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CIRCUITSUseful design ideas from

Electronics Today.Circuits to get you thinking how to solve

your special task, or just for fun. Frompower control to special effects to

alarms, test circuits, and so on.Plus detailed sections on

crystal oscillators, speakercrossovers and more.

For ordering detailssee below.

Obtain yours now from us directly by using the order card in this issue, or by mailing $4.50 + 45c for postage and handling toMORE CIRCUITS, Electronics Today Magazine, Unit 6, 25 Overlea Blvd, Toronto, Ontario, M4H 1B1. Or if your local magazineshop has ETI regularly, they'll soon be getting MORE CIRCUITS too.

EditorSTEVE BRAIDWOOD BSc

Assistant EditorGRAHAM WIDEMAN BASc

AdvertisingAdvertising Manager

MARK CZE RWINSK I BAScAdvertising Services

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Contributing EditorsWALLACE J. PARSONS (Audio)

BILL JOHNSON (Amateur Radio)JOHN GARNER (Short Wave Listening)

DICK CARTWRIGHT (Servicing)

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INTERNATIONAL EDITIONSElectronics Today International

25-27 Oxford St.. London W1R 1 RF, UK.Editor Ron Harris

Electronics Today International,Ryrie House, 15 Boundary St.,

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Elrad,Kommanditgesellschaft, Bissendorfer

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electronics todayinternational

INCORPORATING ELECTRONIC WORKSHOP4,.......WW.WAWeenVANVe

PROJECTSEASY COLOUR ORGANQuick -to -build light show for your stereo.LCD THERMOMETER 31Low power temperature measurement, and nice readout!LIGHT SHOW COLOUR SEQUENCER 51Nifty unit to adjust lights with last month's voltage controlled triacs.VHF ANTENNA, PART 2 55Something about "man versus the elements" . .

BIP BEACON 59For those who can't see, or even for the darkroom.

FEATURESOP AMPS PART 2 17Continuing our once -in -a -while discussion.INSIDE INFO FROM ULTRASOUND 23How the hospitals justify buying a stereo.ETI COMPUTER CATALOG(UE) 35This year's fashionable computer is dressed in the finest of

NEWS &COLUMNSNEWS DIGEST 4AUDIO TODAY 11What a difference a sum makes!COPS STAC TIMER 63Data sheet on how to take control of your life.STOMPER 65Get in practice for barbeque season with this Softspot.RECORD THAT DX 67Taping helps you identify those real catches: Shortwave World.SERVICE NEWS 71The CEASA is picking up steam.QRM 73A little bit of crying over spilt split -splits.TECH TIPS 75Ideas from our readers.FUN OF ELECTRONICS 78Geiger's counters.

INFO & MISCELLANEOUSMore CircuitsTower's I. T. SRead ETI FREECanadian Projects BookSubscriptions

2 741 Cookbook 6910 ETI Panel Transfers 6916 ETI Binders 7422 Classified Ads 7926 Project File 80

ETI Circuits No. 1 30 ETI Marketplace 81ETI Back Issues 53 Reader Service Info 82Electronics Paperbacks 54 Advertisers' Index 82ETI T -Shirts 62 Next Month's ETI 82

ETI CANADA - JUNE 1979 3

NEWS DIGEST

8086 Micro KitIntel's distributors are stocked with theSDK -86, a complete 8086 micro-computer system on a boa -d withmemory and I/O systems in kit form.This stand-alone microcomputerallows designers hands-on experiencewith Intel's 8086 16 -bit HMOS micro-processor which offers ten times theprocessing power of the 8080.

The kit includes an 8 -digit LEDdisplay, a 24 -key keyboard, and allother necessary components fromresistors and crystal to CPU. Onceassembled and corrected to a powersupply the SDK -86 is ready to go.

For data memory, there are 2K bytesof 2142 RAM. This can be doubled byimplementing additional devices in thepositions provided. There is also roomfor 8K bytes of program memory usingeither or both of the keyboard andTTY/CRT 4K ROM -resident softwaremonitors included in the kit, or a2716/2316E EPROM/ROM combina-tion. There is a fully -buffered systembus and 22 square inches of the printedcircuit for developing prototypecircuitry.

Programs and data may be enteredthree ways: the keyboard with LEDdisplay, a built-in serial communica-tions interface, or via cable (SDK -C86)to any Intellec MicrocomputerDevelopment System. The develop-ment system approach allows the userto create programs using PL/M 86 orAssembly Language, and download

them for checkout in the SDK -86. Themonitors provide single-step andbreakpoint capability, as well asmemory and register modification andcontrol of the keyboard/display, serialport, and bus expansion interfaces.

The SDK -86 Microcomputer kit ispriced in the US at $780.00 in single unitquantities.

Fast RAMsIntel Corporation claim they have thenext generation of static RAMs, the2115H/2125H 1024 -bit and 2147H4096 -bit static memories. They arefabricated using a new generationprocess called HMOS II to achievemaximum access times of 20 ns and 35ns respectively. These speeds aremore than twice as fast as previousMOS memories of corresponding size.They are the fastest, lowest power, 1Kand 4K static RAMs currently available.Moreover, the new devices are fasterthan bipolar memories of equivalentstorage, and they use considerably lesspower. The 1K devices will be used todirectly replace bipolar memories inexisting product designs and toenhance performance of existing andfuture products. The 4K devices willprovide a fully -compatible perform-ance upgrade for existing 2147applications, as well as unprecedented4K performance for new productdesigns.

Hundred -piece US prices are $9.85each and $62.60 each.

Bell Goes More DigitalBell Canada's DMS-200, first of ageneration of new digital switchingmachines was officially introduced inApril.

The DMS-200 has a capacity of60,000 trunks - more than double thecapacity of any analogue switchingsystem in use. The DMS-200 does notconnect directly to customers lines butrather interconnects with localswitching centres which are in turnused to serve customers.

The new switcher requires only afraction of the floor space ofconventional units and the speakersmentioned that the solid state softwarecontrolled design would lead tosubstantial operational savings.

The DMS-200 actually went intoservice in Ottawa in January and hasbeen operating smoothly since thatdate. Later this year the first DMS-100machine will be opened in Ottawa'slona switching centre at which timecustomers will be able to subscribe tosuch additional features as call waiting,call forwarding and speed calling.

A final member of the DMS family isthe DMS-300, which will providegateway switching service to countriesoverseas.

50 MHz Freq CounterThe Max -50 is a 50 MHz, 6 -digitfrequency counter, about the size of apocket calculator. Operation isautomatic with lead -zero blanking anda choice of two power sources.

Input is sampled for 0.1 second,readout updated 6 times per second.

For further information pleasecontact: Len Finkler Limited, 25 ToroRoad, Downsview, Ontario, M3J 2A6.

Concentration -Difference EngineTokyo Institute of Technology has dev-eloped the first vehicle to be driven byconcentration -difference energy. TheCDE engine uses heat given off whena solution of salts decreases in concen-tration, caused by vapour absorption.The fuels are pure water and the enrich-ed aqueous solution of inorganic salts.Maximum speed of the prototype veh-icle is about 20 kph, but that's a start.

4 ETI CANADA - JUNE 1979

Triac DriversTwo new single -chip, optically -isolated triac drivers, with zero voltage -crossing capability, have beenintroduced by Motorola. Designatedthe MOC3030 and MOC3031, thedevices are designed to drive up to 55amp triacs in the interfacing of logiccontrol systems to equipment poweredfrom a 110 Vac line. The MOC3030/31scontain gallium -arsenide, infraredemitting diodes, optically coupled to amonolithic silicon chip incorporatingthe detector, triac driver and zero -crossing circuitry.

Zero -crossing protects the triacs andload equipment from inrush currentsthat are generated when triacs aretriggered at near -peak voltage andgreatly reduces potential RFI/EMI.

The trigger current required toon output is 30 mA (MOC3030) or 15mA (MOC3031). US 100 -up prices are$1.80 and $2.37.

Cesco Micro CatCesco has published a new 48 pagemicrocomputer catalogue describingmicrocomputer and microprocessorproducts available from manufacturerssuch as Texas Instruments, Motorola,Signetics, AMI, RCA, Intersil,Commodore and Apple. This catalogueincludes the latest microcomputers,pms keyboards, printers, displays, diskdrives and software. The Micro-computer systems range from thepersonal Pet and Apple to the AMPLprototyping unit. Available free bywriting to Cesco Electronics Ltd, 4050Jean Talon St. West, Montreal, Que,H4P 1W1; or to the Toronto, Ottawa orQuebec City branches.

Exporting To JapanThe Japan External Trade Organiza-tion has recently published a directoryentitled "Exporting to Japan, 1979"which includes a complete list ofproducts that Japanese companieswish to buy from foreign sources.

The bulk of the products listed in thedirectory fall into the categories of foodstuffs, machinery, textile products,sundry goods, metal products,chemical products and precisionmachines.

For those interested in receivingpersonal copies, further informationcan be obtained by contactingOverseas Courier Service, 222 NorthQueen Street, Etobicoke, Ontario M9C4Y1; telephone 416-626-2968.

Horizontal CardMounting SystemThe increased popularity of largeformat microprocessor boards such asIntel, S100, S50, Motorola, Exorciserand Double Eurocard has meantan increase in the height of cardhousing required.

To facilitate the mounting of any ofthese boards in a standard 3U highframe, Vero Electronics haveintroduced a Horizontal Card MountingKit. Designed for use with Vero 3A, 3Cand KM4C card and case frames, the kitconsists of two mounting plates andeight moulded feet. These can bepositioned anywhere in the frame tosuit the required size of board. Clip -in

guides to fit the mounting plates arealso available. Standard boards mayalso be mounted vertically within thesame system as the horizontal mountedboards.

Electronic Packaging Systems, POBox 481, Kingston, Ontario, K7L 4W5.Telephone 613 549 5152.

Two Chart RecordersWebster Instruments has two new chartrecorders:

The Techni-Rite Model TR-711single channel chart recorder providesa frequency response of dc to 125 Hz;

multiple chart speeds in 3 ranges of 1and 2, 5 and 10, 25 and 50 mm persecond; sensitivities of 10 mV/div.,100 mV/div. and 1 V/division and aninput impedance of 500 k ohms.

Writing is by a thermal stylus on heatsensitive chart paper. The stylusfeatures a ruggedized two piece coaxialconstruction that will withstand mostphysical abuse.

Calibrated chart width is 40 mm with40 divisiors. Chart length is 65'. Leftand right hand event markers, actuatedby external switch closure, areoptionally available, as are a carryingcase, plug in chart rewinder, onesecond timer, remote control chartdrive, and aninverter for 12 VDCoperation.

The TR-711 is 4" square by 121/4" longand weighs 10 lbs.

A two channel oscillographicrecorder, the Gulton TR-725, offersseven switch selectable sensitivitiesfrom 10 to 1000 mV/div.; fourpushbutton chart speeds of 1,5,25 and50 mm/second; frequency response ofdc to 100 Hz (-3dB) for each 50 mmchannel. Additionally, Position, Gainand Stylus Heat controls are includedon the front panel.

A single event marker is supplied thatis switch controlled by either a one -second timer or by a pushbuttonmanual control.

Rugged coaxial thermal styli areprovided that are extremely resistant todamage from improper handling. Thestyli are guaranteed for six months.

A plug-in chart rewinder is available,as are a variety of useful options andaccessories.

For more info contact RogerWebster, Webster Instruments Ltd, POBox 427 Port Credit PS, Mississauga,Ontario, L5G 4M1. Phone 416-275-2270.


Introducing theTROUBLESHOOTER3-1 digit 11111DMM$179** Suggested Canadian price. Duty and

federal sales tax included. Subject tochange without notice. Fluke DMM'sare represented in Canada exclu-sively by Allan Crawford AssociatedLtd., and are stocked and sold byauthorized distributors coast -to -coast. Individual distributors maysell at other than the suggestedprice.

We call our new8022A hand-held digi-tal multi -meter the"Troubleshooter" be-cause it provides all themeasurement functions you normallyneed: high ohms, low ohms, AC voltage,DC voltage, AC current, and DC current.

And it's packed in a small, light -weightimpact -resistant plastic case with circuitrydesigned to withstand both physical shockand electrical overloads.

Even the razor sharp 31/2 digit LCD readoutis made to handle the extremes of humidity,temperature and vibration.

For extra convenience and safety theprobes feature Fluke's exclusive fingerguards and shrouded connections, dis-couraging accidental contact with circuitvoltages.

And it's so handy to pick one up. The 8022Ais in stock right now at Fluke distributorsacross Canada.

FLUKEO

Buy FLUKE from

ISH COLUMBIAVancouver: ACA Electronic Centres

Allan Crawford Associates Ltd. 604/294-1326Victoria: Queale Electronics Ltd. 604/388-6111Nanaimo: Queale Electronics Ltd. 604/753-1124Vernon: Interior Electronics Ltd. 604/545-2394Kelowna: Interior Electronics Ltd. 604/860-0585

ALBERTACalgary: ACA Electronic Centres

Allan Crawford Associates Ltd. 403/230-1341Edmonton: Cardinal Industrial Electronics Ltd. 403/455-4122

SASKATCHEWANCardinal Industrial Electronics Ltd. 403/455-4122

MANITOBAWinnipeg: WES Ltd. 204/632-1260

ONTARIOToronto: ACA Electronic Centres

Allan Crawford Associates Ltd. 604/294-1326Ottawa: Allan Crawford Associates Ltd. 613/829-9651Sudbury: Sonic -Northern Ltd. 705/674-5691Timmins: Sonic -Northern Ltd. 705/264-1228

QUEBECMontreal: ACA Electronic Centres

Allan Crawford Associates Ltd. 514/670-1212

NOVA SCOTIAHalifax/Dartmouth: Allan Crawford Associates Ltd. 902/469-7865

CardonDistributeAntennaCardon Import Canada Ltd has beennamed officially the exclusiveCanadian distributor for Anetnna Incproducts.

For more information, write toCardon Import Canada Ltd, 95 McNabSt. North, Hamilton, Ont, L8N 3C8. Tel:416-527-1040.

Crowbar SCRsMotorola has announced a new seriesof SCRs - type numbers MCR67through MCR71 - the first in theindustry to be specificallycharacterized and specified for"crowbar" applications.

The new devices are accompanied bydata sheets which now provide a graphdetailing Peak Capacitor DischargeCurrent - a plot that indicates peakdischarge current as a function ofpower supply capacitordischargetime.This permits power -supply designersto select the specific SCR whose peakcurrent characteristics are capable ofhandling the characteristics of theirparticular supply.

ImagingDevicesA forty-eight page product guideproviding tabulated data and outlineconfigurations for RCA's standard lineof Imaging Devices, designed for use incommunications, industrial,consumer, and military applications,has been released by RCA Electro-Optics and Devices.

Copies of the IMD-100 productguidemay be obtained by writingto RCA, Box3200, Somerville, New Jersey 08876, orby calling 717-397-7661, ext 2712.

Tunable FilterA tunable band-pass filter, for use inaudio and vibration analysis or forcontrolling random noise, has beenintroduced by Krohn -Hite Corporationand is available in Canada fromWebster Instruments Ltd.

The Model 3500 filter offers anunlimited selection of pass -bandwidths, plus independentlyadjustable high and low frequencybreak-points, over the range of 20 Hz to200 kHz. Insertion loss isOdBwithin thepass -band with attenuation slopesof 24

NEWS DIGEST

No it's not the ETI capuccino-expresso machine! It's the VG EELS electron energy -loss spectrometer, This instrument was developed to identify extremely thin films ofabsorbed molecules, and is believed to be the first to direct at the surface a beam ofelectrons which are of low energy - typically of only 2 to 5eV - to eliminate the riskof damaging the adsorbate. Identification is by measuring the kinetic energy lcst bythe reflected beam.

More info from Paul Robinson of Datacomp Electronics at 416-533-2381.

dB/octave outside the pass -band.The model 3500 offers a 4th -order

Butterworth (maximum flatness)response for frequency domainfiltering, plus a "Low 0" (damped)response, -or pulse and transientfiltering. Maximum attenuation isgreater tha-) 60 dB, and irternally-

gene-ated hum and noise is typicallyless than 200 microvolts RMS.

Floatirg (ungrounded) operaticn isswitch selectable.

For more information, contact RogerWebster, Webster Instruments Ltd POBox 427, Port Credit PS, Mississauga,Onta-io L5G 4M1. Phone 416-275-2270.


Wire-WrapkitA wire -wrapping kit including a newwire wrapping tool, a roll of wire -wrapping wire, and pre -stripped wire in4 popular lengths, is now available.

The tool model WSU-30 is acombination tool that wraps andunwraps 30 AWG (0,25mm) wire on .025(0,63mm) square pins. It strips 30 AWGwire using handy built-in stripper. Thewire is Kynar insulated silver-platedcopper. Supplied in the kit area 50ftrollplus pre-cut and stripped wire ininsulated lengths from 1-4 inchesstripped 1 inch on each end. Availablewith blue wire as Model WK -2B, whitewire as WK -2W, yellow wire as WK -2Yand red wire as WK -2R.

For further information, Len FinklerLimited, 25 Toro Road, Downsview,Ontario. M3J 2A6. Phone: 416-630-9103.

An Apple For TheTeacher,Teachers PET,Etc.

The Cluster/One is a new system whichinterconnects up to 30 Apple II,PET, or TRS-80 computers. The com-puters then share the resources of thesystem - disk storage, quality printing,etc.

The hardware that you get for theUS price of $4500 includes a dual 8inflexible disk drive, console computer(actually a PET) with expanded RAM,and controller for the interconnectionbus. For each remote computer there isa board with the necessary hardwareand software; this connects to thecomputer without modification.

The maximum distance to the farth-est remote station is 250 ft.

Nestar Systems Inc, 430 ShermanAve, Palo Alto, CA 94306; 415-327-0125.

UHF Modulator

A video modulator for use with videogames or personal computers is availablefrom M&R Enterprises, PO Box 61011,Sunnyvale, CA 94088.

The Sup'R'Mod II comes with coaxoutput and twin -lead balun, and is pre -tuned to UHF channel 33. It needs +5to +12 V dc power supply.

NEWS DIGESTData LoggerThe Fluke 2200B data loggerfrom AllanCrawford Associates featuressimplified programming and expandedalarm capabilities for voltage, currenttransmitter, thermocouple, and RTDinputs.

You can preset up to four limit alarmsfor each channel or group. Aprogrammable internal clock providestime of day in hours, minutes, andseconds up t 24 hours with precisescancontrol. And a unique program listdocumenting the exact programparameters and limits is available fromthe on -board printer at the touch of abutton. Alarms, clocks, and programlist are all included in the standard2200B package.

The system is ready to go in theapplication of your choice with a 10 -channel low level scanner and highperformance A -D converter, featuringlow thermal offset voltages and 1

microvolt resolution. It comes with aniso-thermal input connector which canbe used to connect voltage inputs andup to four types of thermocouple inputssimultaneously.

The basic 2200B is equipped for 60 -channel operation or may be expandedto 100 channels using a ScannerExtender Chassis available separately.

Vancouver DascoDasco Products maintains sales officesin Vancouver, Calgary, Winnipeg,Toronto, Ottawa, Montreal, QuebecCity, Saint John, Halifax and St. John's.Dasco Date Products Limited have anew showroom and warehouse at 8495Ontario Street, Unit 304, Vancouver,B.C., V5X 3E8. The telephone number is604-324-3446 and the telex number is04-54252.

S100 UniversalMicro processorBoardA new low-cost prototyping boardcompatible with the S100 Micro-processor Bus System, is now availablefrom Electronic Packaging SystemsLimited.

The S100 board layout has beenoptimized for flexibility, and as amemory board will hold up to fifty-two16 -pin DIPs. In moregeneral use,thirty-six 16 -pin, plus eight 24 -pin, plus two40 -pin packages.

The board is produced from copperclad epoxy glass material and is fittedwith 50 + 50 gold plated contacts at.125" pitch.

Display Decoder -DriverA new chip (ICM7211) from Intersil is anon -multiplexed 4 -digit BCD -to -LCDdisplay -driver for use in low -powerapplications, and the companionICM7212 is intended as a driver/decoder for LED displays.A new chip (ICM7211) from Intersil is anon -multiplexed 4 -digit BCD -to -LCDdisplay -driver for use in low -powerapplications, and the companionICM7212 is intended as a driver/decoder for LED displays.

The ICM7211 device features directdrive to an LCD display and contains acomplete on -board RC oscillator forthe LCD backplane frequency. Noexternal components are required. TheICM7212 LED driver directly interfacesthe display without multiplexing andthus no RFI is generated. High (8mAtypical) drive current contributes todisplay brightness. A brightnesscontrol line is available for adjustmentof light intensity via a potentiometer.

CMOS construction requires onlyminimal power, typically 10 uA at 5VDC. The ICM7211 is a pin -for -pin,

function -for -function equivalent to theSiliconix DF411, and additionally, iscapable of either CODE B orhexadecimal decoding. In eitherdecoding mode, the devices carry a fullnumeric display function in addition toa limited alphabetical display (A, B, C,D, E, for the ICM7211/12 hex mode, orE, H, L, P, blank for the ICM7211/12Code B mode). The new chips may beganged or cascaded to allow for 8,12 or16 -digit displays. Applications includelow-cost direct interface betweendigital systems and microprocessors tothe LCD or LED displays; 3 -1/2 -digitBCD readouts for A/D converters;instrumentation displays such ascapacitance meters, counters, DVMsand DPMs; and battery -powereddigital systems. Both the ICM7211 andICM7212 are available in 40 -pin plasticpackages. Prices in 100 -unit quantitiesare $5.60 for the ICM7211 LCD displaydriver and $3.45 for the ICM7212 LEDdevice.

Intersil, Inc., 338 Queen street East,Suite 208, Brampton, Ontario L6V 1C4Phone 416-457-1014.


Dual -Channel ScopeA new low-cost 12 MHz dual -channelgeneral purpose oscilloscope, theGould/Advance model 0S253, hasbeen introduced by Allan CrawfordAssociates Ltd.

The 0S253 features ease ofmaintenance, portability, ruggedness,and a two-year warranty on parts andlabour.

The vertical amplifiers feature2mV/cm sensitivity with dc and accoupling, sum and differenceof thetwochannels with channel 2 inversion andX -Y modes. Horizontal sweep rates are

fully adjustable over 18 ranges from 0.6microsecond/cm to 2s/cm, with a X5expansion giving a fastest sweep rate of100ns/cm with no loss of accuracy.

Triggering is ac coupled from aninternal or external source, positive ornegative slope and variable manuallevel control. Bright -line operation isavailable to give a trace in the absenceof signal or when the selected level isoutside the range of the input signal.

Additional facilities include dc -coupled Z -modulation input, calibratoroutput and a front -panel trace -rotatecontrol.

Cable AssembliesCable assemblies for testing orconnecting circuitry within a board orfor jumping from board to board,featuring rainbow color coded flatcable have been introduced by OKMachine & Tool. They use 26 AWGstranded conductors soldered andepoxy encapsulated to popular top -entry plugs. Plugs are available in 14and 16 -pin Dlp configurations.'Pins aregold plated phosphor bronze forperformance and durability. Doubleended configuration available in 2", 4 "and 8" lengths. Single endedassemblies are offered in 12" and 24"sizes.

For further information contact: LenFinkler Limited, 25 Toro Road,Downsview, Ontario. M3J 2A6 Phone:416-630-9103.

ASCII -AlphanumericDisplaysLitronix have introduced two'Intelligent Displays', the DL2416 andDL1414. They accept ASCIIinformation from a computer systemdata bus, store it, and convert it toletters on LED alphanumeric displays.Each module displays four letters andmodules may be placed side -by -side topresent words, phrases, or sentences.

In large quantities the manufactureexpects the Intelligent Displays to costonly $1.00 to $1.50 morethan thecost ofLED characters alone. The US pr ce in1000 -piece quantities for the DL2416(0.16 inch characters, aftermagnification) is $26.00 each, and forthe DL1414 (0.112 inch characters)$13.00 each. Both units are availablefrom stock.

Zentronics PhoneZentronic's new phone number is 416-676-9000.

Display TerminalsVolker -Craig Limited has introducedtwo new microprocessor -basedasynchronous data terminals.

The Model VC4152 is compatiblewith Digital Equipment Corporation'sVT52 display terminal and features adetachable upper/lower casetypewriter keyboard, 1920 characterdisplay and data rates to 9,600 baud.Additional features not on the DECVT52 include a 25th status line.character highlighting, and 10 specialfunction keys. Hold screen mode anddual mode keypad are selectable fromthe keyboard and a transparent tapemode switch is standard to allow theoperator to display all 128 ASCIIcharacters, an aid in debuggingsoftware and solving difficultcommunication problems.

Other available options includegraphics. split speeds, a bi-directionalserial peripheral interface controlledfrom the CPU or keyboard, parallelinput for bar code readers orperipherals, and numerous keyboard -character fonts (French, German,Swedish, etc.).

The VC4152 is manufactured itCanada by Volker -Craig LimitedDelivery is 12 weeks. Unit price is

$1,850, with distributor and OEMdiscounts up to 45%.

The Volker -Craig model VC415APLoffers both ASCII teletypecompatibility and full APL overstrikecapability switch selectable. Theterminal features a buffered line editmode for preparation of data, andselectable independant window (splitscreen) for host responses so existingscreen data is not erased duringprogramming operations. Atransparent tape mode switch enablesthe display of all 128 characters and thestandard detachable terminalkeyboard is typewriter paired. Anoptional keyboard package includes a16 key numeric pad and 12 specialfunction keys.

Other available options include serialand parallel peripheral interfaces andcoloured display screens (amber,green).

Delivery is 12 weeks. Unit price is$1,850, with distributor and OEMdiscounts to 45%.

Volker -Craig Limited, 266 MarslandDrive, Waterloo, Ontario, N2J 3Z9. Teo:519 884 9330, or 416 456 2070.


11111111111111111111111111111111111111 111111111111111111

Metermaster R.H. NICHOLS 1

NEW PORTABLE 15 MHzDUAL TRACE OSCILLOSCOPE

3 WAY POWER SUPPLY - 120V AC - 11-30V DC - Rechargeable NI -Cad's

Be ready for the most difficult service calls with this versatile, lightweightoscilloscope. Operates for up to two hours on internal Ni-Cad battery, and thebattery recharges while you run the scope on AC line power.

Fully automatic triggeringHArinrilEXFEATURES: 2 mV vertical sensitivity

Light weight - Only 10 poundsACCESSORIES INCLUDE: Combination 1:1 and 10:1 switchable probes

and vinyl carrying case.

For more information contact Metermaster, 214 Dolomite Drive, Downsview,Ontario, M3J 2P8. (416) 661-3190

Toronto (416) 661-3190 Montreal (514) 337-0425Edmonton (403) 432-7746 Ottawa (613) 238-7007

11111 III all Ell III

I

Now AvailableOUR ALL NEWLENLINEELECTRONICCOMPONENTSCATALOGUE.

60 pages contain-ing more than400 items, allfully illustratedand described.

SEND FORYOUR FREECOPY TODAY!

Please send me your LENLINE Electronic ComponentsCatalogue and the name of my nearest LENLINE Dealer.

NAMEI I

ADDRESS

CITY

PROV CODE

len finkler ltd25 Toro Road, Downsview, Ontario M3J 2A6 630-9103

Le 'MG ldr am=

II

TOWER'S INTERNATIONAL TRANSISTORGUIDE is now available from ETI. We are proud tobe able to bring you this "bible" of transistor data.It contains data on over 13000 transistor types, 2Ns,

k 2SCs, European and "replacement" types. Informa-1 tion includes polarity, material, package and leadI4info, maximum ratings for VCB, VCE, VEB, IC, TJ,

P, minimum FT, HFE, typical use, manufacturerand suggested equivalents.WE RECOMMEND THIS BOOK WITH CONFI-DENCE BECAUSE THIS IS THE ONE WE USE.

IIII

THE KING

OF TRANSISTOR GUIDES

To order use the card in this issue, or mail the couponbelow to: TOWER'S, Electronics Today Magazine,Unit 6, 25 Overlea Blvd, Toronto, Ontario, M4H 161.

OK ETI - I don't want to be in the dark about tran-sistor specs any longer - send me THE KING. Here'smy $8.95 plus .45 for postage and handling. (That's$9.40 if your calculator battery is flat, or 2 for $18.80)

NAME

ADDRESS

O Bill Chargex.Expiry Date

0 Cheque enclosed. DO NOT send cash.O Bill Mastercharge. A/C No

SignatureMr AN' AM, ..Mr AMP AM, AM, AMP


BY NOW IT should be clear that thevariety of signals which actually exist inwhat is presumed to be a two channelstereophonic signal is considerablymore than two, and that they can berecovered in a variety of ways and put tomany uses.

All of the techniques we discussed inthe past two columns dealt withelectronic means and with applicationsto which these means were peculiarlysuited. Now, as promised, a look atsome passive circuitry andapplications, that is systems whichinvolve only the loudspeaker networksthemselves.

SIMPLICITYPassive systems have one very great

advantage over active: they are simple,and therefore cheap. It is the closestthing to something for nothing that I

know of. It requires no additional poweramplifiers, no isolation devices, nomatrixing amplifiers. It also involvesfewer things to go wrong.

The first modern application ofpassive sum -difference matrixing wasthe David Haffler "Dynaquad"'"introduced in the early sixties byDynaco as an add-on device andincorporated into their integratedamplifiers. Essentially it was used as ameans of ambience retrieval. Hafflersreasoned that in the recording ofconcert music especially, that therecording channel picked up not onlyleft -right information, but reflectionsfrom walls, ceiling, rear walls, etc., ofthe hall in which the recording wasmade. These reflections, bouncingaround several times before beingpicked up by the microphone, ortheearconstituted short-term delayed soundswhich were responsible not only for the

AudioTodayDevelopments in audio reviewed by Wally Parsons

tonal character of the hall, but also forour perception of distance from theoriginal sound, through the ratio ofdirect to reflected sound and even ourawareness of size and shape of thelistening environment, by subconciousanalysis of the different time delays.Because of the random nature of thesesignals, many of them appear at therecording microphones in varyingphase relationships to each other, andwhen reproduced through the two frontspeakers are either masked by thedirect sound or are partially orcompletely cancelled acousticallydepending on their phase relationship.

These out -of -phase signalcomponents could be recoveredseparately by extracting the differencesignal. Moreover, this difference signalis available at the speaker terminals ofany stereo amplifier. If a speaker isconnected from the signal output ofone channel to the signal output of theother channel, any difference signalwould result in a current through thespeaker so connected. This is shown inFig. 1.

Fig. 1. Speaker connected to givedifference output.

It will be noted that a leftchannel onlysignal will also be reproduced. Samething for a right channel only signal.This is because the circuit for theambience speaker is completedthrough the parallel impedance of theother channel speaker and the amplifierinternal impedance.

It will be further noted that a centrechannel signal will appear at eachspeaker terminal equal in amplitudeand phase. Therefore, there will be nodifference, and no current will flowthrough the "ambience" speaker.DOWN THE CENTRE

Fig. 2 shows the first Dyna circuitactually used. In addition to theambience speaker, which was normallylocated to the rear of the listener, acentre speaker has been added byinserting it between the left and rightspeakers and ground, and sharing theground return with them. Both left andright channel signals are reproducedby this speaker since it is in a common

L F

I I

Fig. 2. Centre front and difference connections,the "Dyna" circuit.


Audio Todayreturn path. Actually, for a left channelsignal, for example, current will divideat the junction of the three speakers,with part going through the centrespeaker and part through the parallelcombination of the other channelspeaker and the amplifier's internalimpedance. Moreover, since it enteredthe other channel from the return leadside, it is also in reverse phase from itsown channel. To counter this a smallamount of channel blend, usually about6 dB is introduced at the inputs of theamplifiers. Thus a small level signalfrom the other channel appears inopposite phase to the signal leakedfrom the speaker line of the otherchannel.

The result of all this is a very solidstereo image particularly with regard tocentre and near -centre imaging. True,stage width is reduced since with eachchannel being reproduced by its ownspeaker and the centre speaker, thesound source is now a pointsomewhere between them. But it allowsthe left and right speakers to beseparated by a greater distance, andallows good listening over a widerarea.You'll notice also that difference signalwill appear at the junction of the threespeakers and to the extent that theiramplitudes are identical and theirphases are opposite will cancel out,leaving only the rear channel to handlethem. Notice too that if the rear channelis removed, the centre channel can stillbe synthesized with the same circuit....

PHASE ANOMALIES. . .And a good thing too, because aclose inspection will reveal a problemwith the rear channel. Suppose the rearspeaker is connected with the "plus"connected to the left channel "plus".This means that the "minus" will havetohe connected to the right channel

"plus", unless you have a balancedoutput and can connect to the rightchannel "minus", but in that case youwill no longer get a difference signal,but a sum signal.

A left signal will be reproduced by theleft front and the difference speaker inphase. However, a right signal will bereproduced by the right speaker andthe difference speaker in reverse phase.The solution then is either to use aspeaker with two voice coils or twospeakers, as in fig. 3. This is the finalHaffler circuit, with the centre channelremoved, and with two rear channelspeakers connected in series but inreverse phase to each other, but inphase with respect to their respectivechannels, and a resistor to ground fromthe junction point. This is intended toprovide a ground reference, and withthe blending described earlier,remove front channel signals from therear, plus minimize out -of -phasesignals from appearing in the oppositerear channels. If this seems a littleobscure, it should be mentioned that atthe time Dyna was also promoting asystem of 4 -channel encoding to beused with this system.

To use this system on today's stereosources it is often sufficient to connectonly the rear speakers as shown butwithout the resistor, and with or withoutblending. In that case some signal willleak to the other channel, and left frontwill appear also at the right rear out ofphase, and in phase at left rear.Similarly with left front signals. Byproviding adjustable resistances in theseries leg it is possible to vary theamount of rear channel signal, and byinserting a variable resistor in place ofthe fixed one, the amount of blend in therear channels and the ratio of in -phaseto out -of -phase sound can be varied. Inthis case a pair of ganged resistances

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For the best sound ever in your car. The first car stereospeaker with a woofer, a tweeter and a midrange.

Identical in principle to the best home stereo speakers.Jensen's midrange picks up a whole range of toneslost to any other car speaker.

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1 len finkler limited25 Toro Road, Downsview, Ontario M3J 2A6Telephone (416) 630-9103 Telex 065-24010

_ +

R=SPKR Z

Fig. 3. Four, four, four channels from two!

will be required in each of the rearspeaker lines. The effect can be quitedramatic on some programmes. Is itaccurate? I don't know. But then, whatis?

BACK TO CENTRENote, that if the resistor is replaced

with a loudspeaker, we now have thecentre channel arrangement shown infig. 2. If the "minus" lead goes toground you will get a sum signal inphase with the left and .right frontsignals, and it can indeed be used as acentre channel. Series and shuntresistors allow not only adjusting theblend in the rear channels, but also thecentre channel level. Increasing thetotal resistance reduces the blend,while reducing it increases the blenduntil, at zero ohms, each rear speaker ison parallel with its respective frontchannel. By increasing seriesresistance in the centre speaker andreducing shunt resistance you can altercentre channel level while keepingblend constant.

Finally, of course, you can reversephase of the centre speaker and use itasa centre rear channel. It may seem hardto believe at first, but thistechnique canactually firm up the centre channelimage even without a front centrespeaker. The out of phase rearcondition tends to project its imageforward which, in conjunction with thetwo front signals, tend to bring thecentre towards the listener. Ironically,the effect tends to be less dramatic withfront speakers whose imaging isalready outstanding, but the feeling ofroom expansion is still there.

TWO FOR ONEA microphone technique called "M-

S" or mid -side found some use severalyears ago. This involved the use of acardioid microphone facing theperformers, and a gradient, or figure 8microphone arranged so that its planeof minimum signal faced the samedirection. Matrixing the outputs ofthese two microphones (see April andMay) yielded left and right signals. Byreversing this it is possible to producestereo sound from a singlespeaker box.

12ETI CANADA-JUNE 1979

I don't mean one eight feet long, but asmall box of usual proportions. Fig. 4shows how. A singlespeaker facesfrontand reproduces the sum of the left andright channels. A second speaker ismounted on the axis if the first androtated 90°, and reproduced thedifference signal. Essentially, therotation of the difference speakerresults in a sound field which isperceived to come from one side, whichside depending on the relative phase ofthe combining signals. In practice twospeakers are used for the differencesignals and wired in opposite polarityand mounted one above the other andfacing opposite directions. This isnecessary due to the different radiationimpedances of each side of aconventional dynamic speaker. Also,the sum speaker may consist of twospeakers wired in series or parallel, withthe difference speakers mountedbetween them.

Jensen, who manufactured such aspeaker about ten years ago used acomplex network with a tapped coil, butthe simplest and to my mind the best

Fig. 4. You didn't want all those nasty speakerspointing at you anyway, did you?

approach is the very same matrixnetwork we've been discussing.Connect the differencespeakersas youwould rear channel ambiencespeakers, and the sum speakersbetween the junction of the differencespeakers and ground. By varying therelative levels of the sum and differencespeakers you can alter the size of thestereo image.

It is also useable as a centre channelspeaker, because it does not reduce thesize of the main stereo field. The centrechannel image is firm because it isa realimage, while left and right are less welldefined, being virtual images. Thereverse is true of discrete left and rightchannels.

Ever notice how many good thingswere forgotten when audio became aconsumer commodity?

Audio Today Letters

Want to express your views or report on news? Write to Audio Today,ETI Magazine, Unit Six, 25 Overlea Blvd., Toronto, Ont. M4H 1 B1

WP COMMENTSThe large number of handwritten

letters which I receive is a splendidcommentary on typewriter sales in thiscountry. Possibly IBM, Underwood (Hi,guys!) Royal, et al, could use someadvice on marketing from the audioindustry, which has certainly madeheavy inroads into the consumermarket with professional and quasi -professional equipment. In view of thefact that it's hardly likely that anyonewith a typewriter would choose to takequill in hand, I presume that thesepeople do not possess typewriters, andI'm not about tosuggestthat they go outand purchase one just to please me.

However, it does mean that, from timeto time, I receive letters which are, urn,shall we say, difficult to read. Thewriters of such letters, I suspect, often

of a brush-off from otherpublications and even somemanufacturers' reps. Well, they won'tget brushed off here. Many such writersappear to be of somewhat limitededucation, if one uses apparentliterateness as a basis of judgement.The projects which such peopleundertake are all the moreremarkable, then. Perhaps some of themore sophisticated are a little toosmartfor their own good, and would rathertrust the Japanese to do for them.

Then, too, thereare readersfor whomEnglish is not their native language,including many French speakingCanadians. Certainly their English isstill usually a lot better than my French,and suggests a greater level of commonsense throughout the province ofQuebec than in Quebec City itself, or inOttawa.

It occurs to me that many readers,particularly those to whom I'vereferred, might considertheir problemsto be pretty simple, and not worth mywhile bothering with. While it's true thatmany are indeed simple, from my pointof view, they are not so simple from thepoint of view of the letter wr ter, or ofmany other readers who haven't yetwritten. Any reader who takes thetrouble to write with a problem,especially one which he suspects is sosimple that he thinks he might appearfoolish (by the way, that's the main

reason letter writers are indentifiedonly by initials), particularly someonewho does very little letter writing, andmay be working in a non-nativelanguage, then spent seventeen centsin postage, and entrust this to thehazards of the post office, obviouslyhas a problem or comment which isimpertant to him and will certainly getthis department's full attention, if notalways the fastest response.

Which brings us to the first letter. I

hope the writer will read the foregoingin the spirit intended, and will not takeoffence. It's an interesting letter (to me,anyway), but the handwriting isextremely difficult for me to read. All I

know about the writer is that he lives inSt. Lambert, P.O., or just possibly St.Laubert, or St. Lambeth, although I

don't know of these places, and judgingby some of his references, is probably inhis forties or fifties. Anyway, here it is,as best I can read it.

HISTORIC SPEAKERSMaybe what I'm asking is a little bit

too old for you, but 20 or 22 years ago aman named Karlson designed anenclosure that I built in those days withan Electrovoice triaxial speaker.Everybody was in hi fi in those days,stereo was as far as the moon. Maybe inyour files or charts you have the exactmeasurements for it.

As I recall this was the best sound inthe world with a 15" Wharfdale, 8"commercial horn horizontally arrangedon top, and I don't recall the tweeterused. The twin taper pieces formed anexponential curve and were veryimportant, like tuning an organ pipe.

Will it work properly with the newhigh compliance, high efficiency units?I remember the measurements were fora 15", a 12" and an 8" speaker.

I still use a 4 x KT66 output tubecircuit called class AA and a transistorpre -amp. I still prefer the sound of tubetype power amps. Is it obstinacy on mypart or a taste developed over sometwenty years?

St. Lambert (?) P.O.

Probably a bit of both. You're not thefirst to observe some highly desireablequalities among some of the best tubetypes. Historical perspectives can be

ETI CANADA -JUNE 1979 13

most peculiar. In music, we shouldremember that Bach was practicallyunknown in his own time, and were itnot for the efforts of Mendelssohn, wemay never have known that this geniusever existed. The great revival ofBaroque and Renaissance music in thefifties and early sixties brought to lightan incredible amount of rubbish -"music to gather wool by" - whichshould have been left in the archiveswhere it was found, but also unearthedsome real gems. Today's nostalgia forthe fifties and the big band eraconveniently forgets the amount oftrash recorded. Similarly, most of theequipment built in the "old days" wasjust as ordinary and undistinguished inits time as most of today's stuff is now.But there were and are some gemswhich are occasionally revived andgiven the benefits of moderntechnology.

I remember your Karlson speakerenclosure very well. Karlson nevermade speakers, only enclosures, andthey were frequently mated toWharfdale, Electro-Voice, University,and Jensen drivers, and the occasionalGoodman. The design, which isreprinted here from Babani's collectionof speaker design (Fig. 1) is a hybrid ofthe bass reflex and a very short pipeterminated in an exponential slot.Performance is very much related tospeaker compliance and "Q" as in areflex system. Detailed analysis isextremely complex, but the dimensionssuggest a volume in the loadingchamber of about 2.5 to 3.0 cu. ft. and aport area of 78.75 sq.in., which makes itthe same area as a 12" speaker cone.Tuning frequency is probably around50 Hz, but it's hard to figure, especiallysince it's not too certain whether theupper section should be considered asa duct, or a pipe. Probably it's actually abit lower than this.

I would suggest as a starting point, a12" driver with a resonance around 35Hz to 45 Hz, such as one of theGoodman's Audiom series. Since it's asmallish box you don't want a highcompliance driver unless it has a low Qwhich means big magnet. If you wish toexperiment with it, I would suggestmaking the space behind the shelf, andthe slot both adjustable, and alter themboth. I would start with the shelf toachieve the classic twin peak refleximpedance curve, then adjust the slot tocontrol the spread and height of thesepeaks.

I must confess'that none of thesespeakers ever impressed me as much assuch contemporaries as the Electro-

Voice Patrician, a Klipsch-licensedfolded horn, and the original TannoyGRF, a sort of transmission line with ahorn flare, and both designed forcornerplacement.

Anyway, hope this helps, and goodluck.

AUTO SOUNDI'm writing to suggest that you devote

one of your columns to the subject ofautomobile stereo. I have beensearching for over a year to find anefficient way to put a higher poweramplifier in place of the 2 wattsthat runsmy AM -FM now. First, I found a fairlyefficient 85%-95% voltage doublercircuit but even at 25V there wasn'tenough volume for my ears. So I tried tobridge the amplifier (three of fourdifferent but fairly common circuits I

dug from my magazine stack) with asimple phase inverter to theoreticallyquadruple my power. However, I wasnot ever able to arrive at a circuit thatwouldn't violently break into oscillationthe moment a speaker was attached.

Next I found the NE 540, aninteresting device, but lack of data on itspin configuration helped me send fourof these little beggars to an early grave.

I finally came across an excellentcircuit for a simple amplifier (from thepages of Audio Amateur, hasa fairly lowparts count and can be used at anyvoltage from ±15V up to whatever isnecessary for your particularapplication by only increasingcomponent ratings and adjusting twobias pots. I'll send you this circuit if youare interested) which retains highquality, its only drawback being that forautomobile use it is difficult to create anegative supply.

Digging through Wireless World andETI Circuits #1, I found two circuitswhich claim to deliver a complementarynegative voltage. I have not been able toget either circuit to work at more than acouple of milliamps before the negativeheads down to zero. Have you anyexperience with generating negativevoltage at amplifier type currents (33mA to 2 A) or could you direct me tosome literature on this subject?

You expressed a desire for someinput a few issues ago on preamps. I amcurrently building one from an article inAudio magazine which just about fitsmy idea of what a preamp should be.That is, there are no tone controls,which I believe aren't necessaryanyhow in a good quality system. Itdoes however incorporate a rumblefilter, a centre channel output, and

keeps hum down toa minimum by usinga second chassis to house the powersupply.

Another subject that I would like toknow more about is one you discussedbefore. Tape decks and associatedcircuitry. You answered one reader'sletter with the commentthat design wasfairly dependent on the recording headitself as well as the type of recordingsystem. Could you delve further intothis some time? I haven't seen much inthe way of explanations of thecharacteristics of the recording head orthe effect of speed and tape size on thesignal being recorded.

Well, this letter, believe it or not,started out to be a short series ofcomments. So I'll just sum up by sayingyour column is becoming my favouriteETI feature. Thanks for your time.

B.D., Victoria, B.C.

The trouble with cook -bookengineering is that combining recipesdoes not result in the sum of the two, butsomething else entirely. Usually acridsmoke. Collections of circuits,including ETI's are intended as sourcesof circuit information, but cannot justbe strung out one after the other and beexpected to work.

Looking first at your power supplyproblem, I can't for the life of me figureout why you would even consider usingeither one. The WW circuit (Fig. 2)couldn't possibly deliver any kind ofcurrent. Or were you expecting the 555to operate as a current source. As forthe ETI circuit (Fig. 3) this is simply aninverter with a doubler output and apositive ground. What you require is abalanced supply, and on the same page(page 50) of the same ETI Circuits #1,and immediately following the circuityou used, you will find a circuit for a DCto AC inverter. It uses an astablemultivibrator driving a power amplifierdriving a step-up transformer with acentre -tapped secondary. Follow thiswith a rectifier and filter and you have abalanced DC supply.

Returning now to the source of yourproblem, required audio power, I

should like to draw to yourattention thefact that I am using a 10 Watt amplifierfor speaker measurements, and haveno difficulty generating enough powerat 20 Hz to cause violent vibration of thefloors, even with an inefficient speaker.The kind of sound levels you seem towant in thecarkind of scares the hell outof me. I'm just glad you drive on BCroads, instead of Ontario. Anyway, witha 12 Volt supply, assuming an amplifiercapable of a voltage output of Vcc -2v,


Audio Today

P -P that gives 10 V P -P, or 5 V peak, or3.5Vrms. Into 4 Ohms this will deliver3 Watts. Or into 8 ohms we have 11/2W.Now with a bridge arrangement you willget twice the voltage across the speaker,and thus four times the power, for 12Winto 4 ohms or 6W into 8 ohms. Butthis requires that you have truly out ofphase inputs (ie: differential ampinputs), AND amp outputs rated forhalf the impedance driven by the bridgeset-up (or less), ie, 2 or 4 ohms respec-tively. Otherwise you won't get twicethe voltage as hoped. Note that if youwant you can get out more acousticpower simply by connecting more

SQUAREWAVEDRIVER

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speakers in parallel with the first, againif the amp will handle it. That is, two 8ohm speakers look like 4 ohms, three8 ohmers look like 2.7 ohms etc. Inother words, bridging works if all con-siderations are taken care of, but it'snot the only way to get mor volumewith a fixed power supply. But thisis a topic for a whole column by itself.

I don't agree that if a system is of highquality there is no need for tonecontrols. Tone controls are forcorrection of programme sources notequipment defects. If your reasoningwere correct there would also be noneed for a rumble filter, since good

D2

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equipment would not contain anyrumble. This sounds like either theBurwen or the Bongiorno circuits, bothof which are very good.

No, I will not delve further into tapeelectronics right now since there is noroom. But it is on my list of subjects.

Letters like this one are particularlywelcome, as long as you don't mindbeing shot down occasionally. Afterall,ETI readers are all adults, even the kids,and as such can handle a little straighttalk, right?

Yes, I'd like to see the AA circuit.Thanks for the offer.

Fig. 2. A couple of inverters that won't do the trick.

+DC SUPPLY

INPUT

D3

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01 - Small signal N.P.N. Q2, 03 - Output transistors

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,-. / Base optionalDia. to suit 12" to 15" Speaker

'w .7 ° . -'N'' ''' '0 '0 " '0 .0' r9i F, r sil 1. g ,1 1:, g f.o . 'r. in a 'Lr, ../3 'r..' c --1; 2 Fig. 1. (letters) Dese is de planz for da box, by Karlson, reprinted from Babani's "Hi Ft Loudspeaker Designs". If you're wondering why Fig. 2.

appears before Fig. 1 it's because Gail put it in the wrong place. However, we have that problem solved for next month, she's going to ourEnglish office, and we've got a new artist, Sarah.


HANSENMULTI -

METERSMULTIMETER MODEL AT -210The model AT -210 is a handy type 100KOhm Per Volt High Sensitivity VOMdesigned for wide range measuring andchecking.With its solid meter movement, highreadable scale and the other many ex-cellent characteristics, accurate measur-ing and checking are available.

MINI TYPE MULTIMETERMODEL AT -1The model AT -1 is a mini type VOMdesigned for the subsidiary instrument ofthe engineers or technicians. With its solidcase, high readable scale and the othermany excellent characteristics, accuratemeasuring and checking are available.

Write today for complete details onthese and other Hansen meters.

Name & Title:

Co. Name

Co. Address:

City

Prov

Postal Code

HANSEN ...mainly because of the meter!

len finkler limited25 Toro Road, Downsview, Ontario M3J 2A6Telephone (416) 630-9103 Telex 065-24010

How to read ETI FREE inthe comfort ofyour own....

library.

1. Find a local (or school) library.2. See if they take Electronics Today.3. If not, continue with these steps.4. See if they take any of those "other" electronics magazines.5. Find the librarian responsible for magazines.6. WARNING. Do NOT be offensive. After all it's not his or her fault that they'venot seen ETI, even though the magazine is incredibly popular, informative andfamous. Not to mention full of useful projects, interesting explanations of newtechnology, news, with columns on audio, ham radio, shortwave and much more.7. Politely convince the librarian that ETI is incredibly popular, informative andfamous. Not to mention full of useful projects, interesting explanations of newtechnology, news, with columns on audio, ham radio, shortwave and more. (It isespecially easy to win this debate if you have noticed in step 4 that they do!).8. Now lay this one on them! They can get 7 issues of ETI for FREE, so as tohave a chance to evaluate it and see for themselves how popular the magazinewould be on their library shelves. All they have to do is fill in the coupon belowand send it to us.9. Note: if librarian is bigger than you, and looks fierce, simply leave couponbelow on librarian's desk.

Dear Librarian:Electronics Today is a magazine aimed at electronics enthusiasts of all levels,

from beginner and student, to teachers, technicians, and engineers who areprofessionally involved in the field. Something else you should know is that weare a Canadian magazine, and we' e been around for 2Y2 years now. That meanswe not only have editorial related to electronics, we have information relatingspecifically to Canada. The ads too are Canadian, and we find our readers read-ing these intensely to find out where to get what in their own country.

In deciding whether to give us a shelf space, you no doubt have to decideif enough of your patrons will be interested in us. If you take Popular Elec-tronics or Radio Electronics, then that decision has been made, for ourreaders are in many ways similar. In fact, our reader survey and letters we receiveindicate that many readers not only like us better, they've "switched" from the"other two"

Please then accept our free "evaluation subscription" offer. We will send youthe next 7 issues free, so you can see how we do.

Thank you.

Mail to: Library Offer, ETIMagazine, Unit 6, 25 OverleaBlvd., Toronto, Ontario M4H1B1.

Librarian:

Library:

Address

Subscription Manager

Offer valid until Sept 30th 1979.Please allow.6 to 8 weeks for first issue to arrive.


Op Amps: Part 2

In the first part of this series Tim Orr discussed the theory and operation of op -amps.This month he moves on to give some circuit applications for this ubiquitous device,and explains how and why it can do what it does!

10k 10k

100k

V IN

V OUT

SINGLE OP AMP OSCILLATOR

This circuit has a Schmitt trigger and a 'sort of integrator' allbuilt around one op -amp. The positive feedback is via the10 k resistors. The 'integration', (the timing) is controlledby the RC network. The voltage at the inverting input followsthat of the RC charging exponential, except that it isconfined to be within the upper and lower hysteresis levels.Thus the hysteresis levels and the RC time constant determinethe frequency of operation It is possible to make the outputsquare wave have a large mark to space ratio. By closingthe switch SW1, the discharge time of the capacitor becomesten times as fast as the rise time. Thus a square wave with an10:1 mark space ratio is generated.

PRECISION HALF WAVE RECTIFIER

Rectifying small signals with any accuracy can be very diff cultusing diodes only due to their forward voltage drop of about0.6 V. However, an op -amp can be used to reduce this voltagedrop to virtually nothing. Consider the circuit shown. There isnegative feedback so that 'virtual ground' circumstances exist.When Vin is positive, D1 conducts to maintain the virtualground, D2 is reverse biased and so the output is just a 100 kresistor connected to 0 V. When Vin goes negative, the outputrises positively, D2 is turned on and D1 turned off. As thevirtual ground is being maintained, the output voltage is theexact inverse of the input voltage. This is true for all negativeinputs. Therefore, the output is composed of positive goinghalf sinewaves. Precision half wave rectification has occurred.In fact the diode error is very small, being equal to

600 mVisurplt..s voltage gain)

ETI CANADA - JUNE 197917

Op Amps: Part 2

Therefore as the input frequency increases, and the surplusvoltage gain decreases, precision falls.

By adding together the original and the half wave rectifiedsignals together in the right ratio, it is possible to fill in thehalf cycle gaps and thus to generate precise full waverectification. The addition of one summing op -amp and threeresistors is all that is needed as shown opposite.

V IN

V OUT

PRECISION PEAK VOLTAGE DETECTOR WITH ALONG MEMORY TIME

The circuit shown has negative feedback only for positivesignals. That is, the inverting input can only get some feedbackwhen diode D1 is forward biased and this can only occur whenthe input is positive. When a positive input signal is appliedthe output of the op -amp rises until the inverting input reachesthe same potential. In so doing, the capacitor C is also chargedto this potential. When the input goes negative, the diode 01becomes reverse biased and so the voltage on the capacitorremains there, being slowly discharged by the op -amp inputbias current and the resistor R (10M). The op -amp used has aMOS FET input, having an exceptionally low input biascurrent of 10 pico amps. Thus the discharge of the capacitor isdominantly controlled by the resistor R, giving a time constantof ten seconds. Thus the circuit detects the most positive peakvoltage and remembers it.

LED BAR PPM DISPLAY FOR AUDIO

The peak voltage detector can be used to control an illuminat-ed audio level monitor having the same characteristics as aPPM (Peak Programme Meter). A bar column of LEDs isarranged so that as the audio signal level increases, more LEDsin the column light up. The LEDs are arranged vertically in6 dB steps. A fast response time and a one second decay timehas been chosen so as to give an accurate response to transientsand a low 'flicker' decay characteristic. The op -amps thatdrive the LEDs are used as comparators. On each of theirinverting inputs they have a dc reference voltage, whichincreases in 6 dB steps up the chain. All of their non -invertinginputs are tied together and connected to the positive peakenvelope of the audio signal. Thus as this envelope exceeds aparticular voltage reference, that op -amp output goes highand the LED lights up. Also, all the LEDs below this areilluminated.

V IN

100k

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01 1N914

V< PEAKENVELOPE

33

16k

862

Ve REFERENCE

ALL741

ALLTIL209LEDS

3608

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tronics or computers to take this excitingnew course. NRI starts you with the basics,gives you a firm foundation to build on. Andyour personal counselor is always available,ready to help whenever you have questions.

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or telephone 416-293-1911

Vref (UPPER)

V IN

Vref i LOWER)

R1

V V4 )V OUT = -R5 I(- +V2 +V3 +R1 R2 R3 R4

D1

D1, D2 = 1N914

2N3819 GUARD RING

470nPOLYESTER

400V

01 = 1N914

V OUT

VIN

VrefLOWER -

11=1

PRINTED CIRCUIT BOARD LAYOUTGUARDRING

VrefUPPER

2N3819 V OUT

CA3140

0V OUT

BASIC SUMMING CIRCUIT (MIXER)

A virtual ground amplifier can be used to mix several signalstogether. The output voltage is a mixture of all the inputs.The amount of an input that appears at the output, inverselyproportional to the input resistor. If the input voltages are fedinto potentiometers before being fed to the mixer, thentheir individual levels can be manually adjusted. This is thebasis of most audio mixers, although the cheaper units use op -amps. Most op -amp mixers will degrade the signal to noiseratio of the signals by more than a good discrete componentamplifier.

WINDOW COMPARATOR

A window comparator gives an output which in this caseis 0 V, when an input voltage lies in between two specifiedvoltages. When it is outside this 'window', the output ispositive. The two op -amps are used as voltage comparators.When Vin is more positive than Vref (upper) the output ofIC1 is positive and D1 is forward biased. Otherwise the outputis negative, D1 reverse biased and hence Vout is 0 V. Similarly,when Vin is more negative than Vref (lower) the output of IC2is positive, D2 is forward biased and thus Vout is positive.Otherwise Vout is 0 V. Thus only when Vin lies within thewindow set by the reference voltages is Vout 0 V.

HIGH PERFORMANCE SAMPLE AND HOLD

It is often necessary to have a circuit that will sample ananalogue voltage and then remember it for a long time withoutany significant degradation of that voltage. This is known as asample and hold circuit and one of its uses is to store the voltagefrom the keyboard connected to an electronic music synthesiser.The voltage is then used to control the pitch of a voltagecontrolled oscillator and so it is very important to have a highperformance sample and hold. A drift of less than one semi-tone, (80 mV), in ten minutes is required. A sample and holdis simply an electronic switch, a storage capacitor and a highinput impedance voltage follower. In the circuit shown, whenswitch SW1 is positive the FET is turned on, and has a resist-ance of about 400R. Thus the input voltage charges up thecapacitor through the FET. When SW1 is negative, the FET isturned off, (pinched off), and can have a resistance of thous-ands of megohms. To get a long storage time the op -amp musthave a very low input bias current. For the CA3140, thiscurrent is about 10 pico amps, i.e., 10-11 amps. Therefore therate at which the capacitor will be discharged by this currentcan be worked out from the equation, C(dv/dt) = iwhere dv/dt is the rate of change of voltage on the capacitor.


Op Amps: Part 2

Therefore:

dv = i = 10-11 22 uVis

dt C 0.47 X 10-6

This is a very low drift rate, much better than we need. How-ever, the actual drift rate will probably be in excess of this,due to surface leakage on the printed circuit board, leakagethrough the FET, and internal leakage in the capacitor. It isadvisable to use a high voltage, non -polarised capacitor in this

LINEAR VOLTAGE CONTROLLED OSCILLATOR

This oscillator is very similar to the triangle square waveoscillator shown on this page, except that this one is voltagecontrolled. The integrator and Schmitt trigger action are thesame as before, but the feedback has been altered. The inputvoltage Vin, is applied differentially to the integrator via theresistor network. The larger the value of Vin, the faster theintegrator ramps up and down. Thus the frequency of theoperation is determined by an external positive control voltage.The frequency is linearly proportioned to this control voltage.

When the output of the Schmitt is low, 01 is off and allthe input voltage is applied to the inverting input. Half of theinput voltage is always applied to the non -inverting input.Therefore the integrator's output ramps downward until theSchmitt flips into its positive state. Now, Q1 is switched onand the voltage at the inverting input is negative with respectto the non -inverting input. Hence the integrator now rampsupwards.

SILENT AUDIO SWITCHING

Sometimes electronic switches for audio signals are required.FETs can be used to perform the switching, but they cancause distortion, the resultant output impedance is not verylow and clicks generated by the switching signal can breakthrough. The circuit shown virtually eliminates all of theseproblems. By using an op -amp a very low output impedance isobtained as well as the possibility of selecting or mixing oneor more of many input channels. Because of the virtual groundmixing, the voltage across any FET that is switched on is verysmall. If the output voltage is 1V and the FETs ON resistanceis 470R, then the voltage across the FET is about 10 mV.When large voltages are applied to a turned on FET, the dis-tortion is large, but if the voltage is small, (10 mV say), thedistortion could be less than 0.1%. Thus the virtual ground mix-ing enables low distortion operation. Lastly, to stop the gen-eration of switching clicks, a time constant of 47 msec hasbeen enforced at the gate of the FETs.

circuit to keep the leakage currents to a minimum. Also, tostop surface leakage a simple PCB trick can be used, that ofmaking a guard ring around the sensitive components.

Normally any potential stored on the capacitor may leakto ground across the surface of the PCB, but if we make thesurrounding surface a conducting track held at the samepotential as that of the capacitor then the potential differenceis virtually always zero, and hence the surface leakage is great-ly reduced.

ON = OVOFF = - 15V

ON = OVOFF = -15V

01,2 = 2N3819

SWITCH TIME CONSTANT 47mS

The next part sees circuits for exponential voltage to current convertors, musical chime generators, triangleto square wave convertors, square wave generators with auto level adjustment and variable mark space ratio -amongst other things.


1?V

A STEP BY STEP GUIDE TO BUILDING OUR

MODULAR DISCO PROJECT

1. FIRST TAKE OUT YOUR MAGNIFYING GLASS

2. BUILD THESE MODULES:

Balanced MicrophonePreamplifier

.44 ,

- ''HOW IT WORKS

Modular DISCO

ModAY Paco

PORTS LIST

Fifty/One HundredPower Amplifier

Microphone onnon

Crony. CorrtiPpe F4glom0

Ceramic CartridgePreamplifier

-VU Meter

- SPEC;ICATiONS -

...Vim.

Power MhiL

Modular Disc

Headphone AmplifierPrefade Monitor

m .-en PARTS LIST

Gone. V100 ROOM°

General PurposePreamplMer

Mixer andPower Supply

=-;

3. RUB YOUR EYES

4. SEND US $3.45

And we will send you completefull-size (ETI- size pages )instructions on these and manyprojects in our

CANADIANPROJECTSBOOK #1

IncludesPostage &Handling

22ETI CANADA - JUNE 1979

Inside InfoFrom UltrasoundUltrasonic sound is being used increasingly in medical diagnosis. By Dr. P.N. T. Wells.

THE importance of ultrasonicdiagnostic methods lies in thefundamental differences between themand other techniques such as radiologyand radioisotope scanning. Thesymptoms of some diseases, and ofnatural conditions such as pregnancy,are best investigated by ultrasound. Itmaps out anatomical cross -sections,measures the performance of the heartand the flow of blood, and identifiesmany kinds of abnormality, includingseveral types of cancer, all withoutencroaching into the body in any way.

Twenty-five years ago, doctorsseeking to investigate the structures ofthe body had no alternative to X-rays.Injections of substances to give bettercontrast were often necessary to obtaininformation about soft tissues.Nowadays, ultrasonic methods havereplaced radiology in helping to solvemany clinical problems: doctors dependon ultrasonic diagnosis, and patientsdemand this kind of investigation. Theprocedures are rapid and painless andnothing enters the body other thanultrasound waves. Unlike ionizingradiations, ultrasound at diagnosticexposure levels seems to be harmless.

BASIC PRINCIPLESMost diagnostic applications ofultrasound depend on the reflection ofultrasonic waves at surfaces betweentissue structures which differ in theirso-called characteristic impedance. Thecharacteristic impedance of a material isequal to the product of its density andthe velocity of ultrasound within it.The densities of soft tissues, about 103kg m-3 (kilograms per cubic metre), andthe velocities of ultrasound withinthem, about 1500 m s-1 (metres persecond), are similar to those for water.When an ultrasqnic wave strikes theboundary between tissues that differin characteristic impedance, a propor-tion of the energy in the wave isreflected in much the same way thatlight is reflected when it meets a changein reflectivity at a surface

Far -side Mid -linestructures structures

Near -sidestructures

1Ultrasonicprobe

Ultrasonicbeam

Near -side Mid -linesignals echo

Displayscreen

Far -sideechoe'

Vertical Iv

deflectionplate

Cathode-raytube

Horizontaldeflectionplate

Electron gun

Basic arrangement of the A -scope system, in use in this instance to show Me mid -line structuresof the brain in their relative position half we between the sides of the skull, as indicated bysymmetry of me deflections of the cathode-ray tube trace. Asymmetrical spacing of thedeflections may mean that disease has brought about a physical change such as a tumour onone side of the brain. The swept -gain generator gradually increases the receiver amplification overeach sweep of the time base to compensate for the attentuation of the deeper echoes byintervening tissues.


The characteristic impedances of softtissues are similar, so the echoes fromtheir boundaries are very small. Forexample, only about 0.5 per cent of theenergy striking the boundary betweenkidney and fat is reflected. Such echoesare large enough to be detected by asensitive receiver. But almost all theenergy crosses the boundary andis available for reflection by deeperstructures.

Much larger reflections occur atboundaries between soft tissues andeither bone or gas, because of largedifferences in characteristic impedance.These large reflections restrict the use ofultrasound in medical diagnosis. More-over, it is necessary to exclude air frombetween the probe and the patient. Thismay be done either by examiningthrough a water bath or through a filmof oil smeared on the patient's skin.

RESOLUTIONUltrasonic echo -ranging techniquesdepend on the measurement of the timeinterval between the transmission of a

brief pulse of energy and the receptionof its echo, just as in radar. In anyimaging system, whether using light,ultrasound or any other kind ofradiation, the resolution is limited bythe wavelength of the radiation. It is forthis reason that ultrasound, as opposedto sound, is used in medical diagnosis.We need to visualize structures of only a

few millimetres in size, so that wave-length has to be around a millimetreor less. In soft tissues, it is about 1.5mm at a frequency of 1 MHz andproportionately less at higherfrequencies. The highest audiblefrequency, about 20 kHz, has awavelength of 75 mm. In principle,the performance might appear likely toimprove as the frequency is increased.But ultrasound is attenuated as it travelsthrough tissues and the rate of attentua-tion also increases with the frequency,so we have to compromise betweenbetter resolution and reduced penet-ration.

PULSE -ECHO TECHNIQUESIn an ultrasonic instrument for diagnosis,a probe containing a piezoelectrictransducer converts electrical signal intoultrasound waves for transmission intothe patient. It does the opposite forechoes.

The simplest type of ultrasonic pulse -

echo diagnostic system is called the A -

scope. (See Fig. 1). The clock triggersthe transmitter, which feeds a briefpulse with a large amplitude to thetransducer. Echoes return to the probefrom those reflecting surfaces inside thepatient that lie along the ultrasonic

24

Clock

Time -basegenerator

Motor -gearbox

driveDeflection

plate

Transmitter

Receiver

Grid

Cathode-ray tubewith fibre -optic

face plate

Brightness -modulated trace

Idling rollerConstant -speed paper drive roller

Ultrasonicbeam

Ultra -violet

recording paper

Ultrasonic probe

Heart

Time -position recording system based on the B -scope display, shown in use for echocardiography.The fibre -optic face plate of the cathode-ray rube collects enough light to produce a self -developing trace on ultra -violet recording paper.

Supporting structurewith articulated !GAsand slides allowingselection of scan plane _

Articulatedarms

V/0

Resolvers

-Iiio...

Ultrasonic probe

Typical path ofultrasonic beam

Ui k

Line ba-t.(11.,..tatots

Trani:miner

Grit

Tyler ii scar, hilt.

Two-dimensional scanner and B -scope display system studying a foetus. The time -base generatorsare driven by electrical outputs from a series of resolvers that measure the position of the ultra-sonic beam as it moves across the patient Horizontal and vertical time -bases combine to deflectthe spot in such a way that its movement across the display corresponds to the movement of thebeam. Echoes received as the probe moves over the patient produce a cross-sectional image in aplane corresponding to that of the scan. In this example, the image is built up on the screen of anelectronic storage tube for direct viewing

beam. Electrical signals from the echoesare amplified by the receiver andapplied to the vertical deflection platesof the cathode-ray tube; the time -basegenerator, which is triggered intooperation by the clock at the instantthe ultrasonic pulse is transmitted bythe probe, is connected to thehorizontal deflection plates to drive thespot on the display at constant speed

from left to right. In this way thebeam sweeping across the display isdeflected vertically at intervals along thehorizontal axis, corresponding, indistance from the start of the sweep, toecho -producing surfaces at variousdistances along the ultrasonic beam. Aspecial circuit in the receiver increasesthe amplification of the deeper echoesto compensate for their attentuation by


Inside Info From Ultrasound

Head oftwin 2

Abdomenof twin 2

Head oftwin 1

Placenta

Abdomenof twin 1

A two-dimensional scan (right) reveals twins at about 25 weeks of pregnancy. The placenta onthe anterior wall of the uterus is clearly defined while the abdomens of the twins, identified inthe explanatory diagram, appear in section.

intervening tissues. The clock operatesat a repetition rate fast enough to give aflicker -free trace on the display.

The A -scope has clinical applicationsin neurology, ophthalmology andinternal medicine. It allows the depthsof echo -producing surfaces to bemeasured, and the characteristics ofechoes from within structures to bestudied.

Echoes from moving structures, suchas the valves of the heart, oscillate inposition along the horizontal axis, ortime base, of the display. In cardiology

Stationary reflector Wave fromtransmitter

1,116:161

(a)

Reflec or movingtowards source

I -*

(b)

Reflector movingaway from source

.11,

Reflected wave,equal in frequencyto transmitted wave

Wave fromtransmitter

Reflected wave,higher in frequencythan transmittedwave

Wave fromtransmitter

Reflected wave,lower in frequencythan transmittedwave

The Doppler effect occurs when a wave isreflected from a moving surface, giving enupward or downward 'shift' in frequency as in(bl and (c).

particularly, patterns of movement cangive diagnostic information. They canbe studied by making recordings withthe aid of a B -scope display (see Fig 2).In the B -scope, the time -base sweep isnormally invisible, but it is brightenedby returning echoes to produce spotsof light on the display in places where,on an A -scope, there would bedeflections of the beam. The positionsof the spots of light correspond to echo -producing structures in the patient, andthe pattern of their movements can bepermanently recorded.

Transmitter

Probe

Transmitting 1.transducer

CROSS-SECTIONAL IMAGESThe B -scope forms the basis of anotherdisplay method, the two-dimensionalultrasonic scanner (see Fig. 31. Theultrasonic probe, instead of being heldin the hand, is mounted on a scanner. Itcan be moved to any position in a two-dimensional plane. In this way it ispossible to arrange for the beam to passthrough structures lying in a chosenplane within the patient, while theposition of the probe and the directionof the beam are measured continuouslyby 'resolvers' mounted in the scanner.The electrical signals from the resolverscontrol two time -base generators,driving the vertical and horizontal beamdeflection plates of a cathode-ray tube.The direction and position of the ultra-sonic beam across the patient controlsthe position of the cathode-ray beamshowing up on the display, related tothe positions of the echo -producingsurface.

A cross-sectional image of thesurfaces can be built up photo-graphically by a camera with an openshutter that record., the bright spots onthe display while the patient is beingscanned. The echo information can alsobe stored electronically.

Two-dimensional scanners in whichthe probe is moved in contact with thepatient produce individual images inscanning times of about 10 seconds,Images can be produced at a muchfaster rate by moving the probemechanically. Images in rapidsuccession allow physiological move-ments to be studied; their main

Receiver

Receivingtransducer

Ultrasonic Foetal heartbeams -1 I

Rate meter

Recorder

Record offoetal Heartrate

One use of the Doppler 'shift' is to monitor the foetal heart. The echoes usually fall in the rangeof audible frequencies.


Inside Info From Ultrasound

importance is in cardiological diagnosis.But although these rapid mechanicalscanners produce so-called real-timeimages, they lack flexibility. Thisdifficulty can be overcome by usingultrasonic probes containing manyseparate transducer elements, operatedseparately or in groups, which canproduce ultrasonic scans made up ofparallel lines or of lines arranged in afan shape, at frame rates of tens persecond.

As well as making it possible to studyrapidly moving structures, real-timescanners can also he used to explorelarge volumes of anatomy in a shorttime. A doctor using one can examine apatient in about a quarter of the time ittakes with a 'conventional' two-dimensional scanner.

The frequency of an ultrasonic wavereflected from a stationary structure isequal to that of the incident wave. Ifthe beam is reflected by a surface whichis moving towards the ultrasonic source,the reflected wave is compressed into ashorter space. This means that thewavelength is reduced. it shows as anupward 'shift' in its frequency.Reflection by a surface moving awayfrom the source gives a downward shift.

This phenomenon, the well-knownDoppler effect, conveniently gives shiftfrequencies that fall in the audible rangewhen ultrasound is reflected by movingstructures in the body such as heartvalves or flowing blood. A simpleinstrument based on this makes itpossible to detect the movement of thefoetal heart. Similar instruments tomeasure blood flow allow peripheralarterial disease to be assessed.

Because Doppler shifted signals arereceived only from structures that move,two-dimensional maps of them can bebuilt up by using a Doppler probe toscan the patient. In this way thedistribution of blood vessels close to thesurface can be studied. Suchinformation may obviate the needfor X-ray angiography, which is a

dangerous and expensive procedure.It can also be combined with other

information about structure positionobtained by the pulse -echo method,making it possible to map out bloodvessels within the body and measure therate of blood flow at the same time.

Work being done to improve the per-formance of the instruments now in useincludes basic studies on the inter-actions between ultrasound and biolog-

ical materials, the development ofreal-time scanners and investigationsof techniques for displaying theinformation. The ultrasonic signals fromdifferent tissues may be characteristic ofthe tissues themselves and in some cir-cumstances it may be possible toidentify them. Improved techniquesinclude colour -coding to demonstratevarious tissue characteristics, and storingultrasonic data in a three-dimensionalmatrix so that any two-dimensionalplane can be selected for display.Analysis of Doppler signals from bloodflow is another promising field; it maysoon be possible to assess the effect ofdrugs on the cardiovascular system.

The clinical value of ultrasonic tech-niques has already been proved, buttheir spread into general, everydayservice will depend on the developmentof instruments that are simple to use.These, paradoxically, may be morecomplicated than the ones we alreadyhave. It will also mean training doctorsand technicians to obtain and interpretresults. But it is clear that ultrasonicdiagnosis is, in many instances, the bestand most economical way of gettingthe information essential to proper careof the patient.

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With a subscription you payonly $14 dollars!

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- ETI Project

Easy Colour Organ

Here's the electronics for a home colour organ to light up your sound system.

It's less sophisticated than the lighting controller of last month, but very in-expensive.

A COLOUR ORGAN is quite simpleto put together, and the circuit de-scribed here enables you to make avariety of different attractive lightdisplays for your sound and peopleparties.

WHAT IT DOESThe basic idea is that three lights

are controlled on or off by the threechannels of our circuit. Each channellistens to a different frequency rangeof the audio. Thus one light willpulse in response to the bass, anotherilluminates with mid -range sounds, andthe last lights for high notes.

Four level controls allow you toadjust overall light level, and eachchannel individually. Up to 200 wattsper channel can be handled by this unit,or more if heatsinks are used (Be sureto insulate the SCRs from the heat -sinks though!)

DISPLAY IDEASVarious displays have been tried.

Two of the most commonly seen aredescribed here. First there's the all -in -one -box type. The box looks like aspeaker box, but the front is coveredwith a sheet of clear or translucentplastic. The type used to cover floure-scent lighting fixtures is attractive.Inside the box are three coloured lights,and the appearance may be made moreinteresting by also enclosing mirrorsor shapes which are then lit up.

The other kind of diplay uses smallflood lights of different colours tolight up parts of the room in time withthe music. A sophistication of thisscheme is to project shapes or shadowswith the lights.

CONSTRUCTIONBuilding this project is very quick

especially using the pcb, and followingthe component positioning diagram.A few notes should be observed. Weused a "pigtail" type holder for thefuse, the idea of which is to allow forreplacement if/when the fuse blows.So attach the pigtails to the fuse, theninsert the two tails into the board.Don't mount it too close to the boardor you won't be able to get the fuse outif need be! About % inch should do.Now puz in the resistors, capacitors

(watch the polarity of some, andtransformer. The SCRs can also be putin, but make sure not to get them toohot as this can damage them. If indoubt, grip each lead with pliers be-tween the body and your iron as yousolder, this will draw the heat away.

The potentiometers can now bemounted, their leads will need to bebent so that the pots can be orientedas shown. (See pictorial). Make surethat R4 clears the fuse and holder!You don't want the pot shaft to be live!

The last step is to wire up the socketsand line cord. Although we have shown


Eli Project

S1

AC

F1

AC

R7 C4 X3

RIM M-

T1

MASTER

R4

C3 X2

R10

IN

11111

R3

Fig. 1. Component positioning diagram.

Potentiometermounting.

a picture of our board not in a box,we strongly advise mounting the unitin a box to keep the wires and socketsetc from floating about.

CONNECTING UPAll that remains is to attach the

audio input to the speaker terminalsof the amp, plug in the lights to thebox, and the line cord to the wallsocket.

SCRposition

N.1.1.3.40,361%.110%.

Circuit board layout.

R5

R9

X1

MID

11; 4147wi11110111111INIVED

-

C2

R8

R2' I R1

LOW

11=11,s-I-! -

111

AUDIO IN

C1

WARNING: THE CIRCUITRYIN THIS PROJECT IS CONNECT-ED DIRECTLY TO THE LINE.HENCE ANY POINT (exceptthe audio input wires) COULDGIVE A NASTY SHOCK IFTOUCHED. THUS ALWAYSOPERATE UNIT IN A CASEAND USE PLASTIC KNOBSFOR THE POTS.

eTCCO-23

ONO OINNO 001010

O

A 71 71)828 ETI CANADA - JUNE 1979

HOW IT WORKSStarting at the input end of the circuit,the sound signal from the speakerterminals is fed to the primary ofT1, and appears at the secondary.A number of things must be said aboutT1. First, it is used to isolate theinput (which is connected to youramp!) from the AC line. It should benoted that the transformer is usedbackwards from its usual orientation,that is to say the 8 ohm winding isnormally the secondary and is hereused as the primary.

Another purpose of the transformeris to ensure that the colour organ lookslike a very small load to your amplifier,thus not affecting normal operation ofthe speakers which are also connected.

Let's now look at the way the restof the circuit works. Figure 3 is asimplified picture of just one channel,with the controls R4 and RI (or R2or R3 depending on which channelwe're looking at) set at maximum.The components R, C, R5 and thetransformer secondary (as an inductor)act as a bandpass filter, so that thesignal reaching the SCR gate is thefiltered version of the input signal,with frequencies outside the selectedband being greatly reduced. Theactual frequency and "width" of thebandpass filter are set by the valuesof the previously mentioned compon-ents. As can be seen by looking atFig. 2, the basic differences betweenchannels are the values of C and R.The higher value C is, the more lowfrequencies are allowed through. So

the channel with C2 has the lowestfrequency response. Notice that Ralso varies from channel to channel,and the overall effect is such thateach channel "listens to " about onethird of the audio spectrum.

OK, now we've got the signal tothe gate of the SCR. When that signalexceeds a certain amount, (about 2V)the SCR "fires" or switches on, allow-ing current to flow through the load,in this case light. Now, the SCRis a rather peculiar device in that itcan only conduct in one direction, andonce it is switched on, it stays onuntil the current through it falls tozero. This of course happens every1/60 second, since it is in the AC linecircuit. (See Fig. 4) However, if thesound level still exceeds 2V in the nextpositive 'A cycle, the SCR will betriggered again, and over an extendedperiod of loud sound the light appearscontinuously on.

Control R4 sets the overall lightlevel, while RI, 2 and 3 allow theindividual adjustment of light levelsof each channel.

Easy Colour Organ

Fig. 2. Circuit diagram for complete colour organ.

C1220u+ T1

AUDIOIN 8R

TOSPEAKERTERMINALS

.1-40

R110k

R3 C2

6k8 lu

--/VW-1R55k6

S1

R9 C3

R2 3k9 20n

10k

FiV R65k6

R10 C4

R3 1k 4n7

"/VVV--I I10k

Fig. 3. Simplified circuit diagram for just one channel.

Signal appears here

\\aNg

Transformersecondary

Signal isfiltered whenit gets here

R C

Fig. 4. What the SCR does relative to the AC supply voltage.If sound signal exceeds approx 2Vduring these times. SCR wins on light

Voltageat AClineinput

;120V RMS)

4_,

A AOne cycle =1/60 sec

SCR doesn't condut, sinceit is a one way deyce

I

Tvnr

R75k6

X1C106

S2

X2C106

X3C106

13E1

S3

LOWERE()

MEDFREQ

HIGHFREQ

1204 ACINPUT

-PARTS LIST

SCRsX1-3 C106

POTENTIOMETERSR1-4 10k

RESISTORS all 1/2WR5-7 5k6R8 6k8R9 3k9R10 lk

CAPACITORSCl 200u/40VC2 luC3 20nC4 4n7

TRANSFORMERTl Speaker Driver Type

1k2 pri, 8R sec.

MISCELLANEOUS3 AC Sockets, AC line cord,Fuse clips and 2A fuse, pcb.


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TEST

The first in a new seriesof 'ideas books'for the experimenter

Contents

Diode CheckerGO NO GO Diode TesterZene, CheckGO NO GO Transistor TestierOuick JFET TestCurrent Gain TesterBasic Transistor TesterSimple Transistor SCRSCR TesterCrystal CheckCrystal CheckerGood Bad Battery TesterBattery TeslerOp -Amp TeslerOp -Amp CheckerCheap Logic Probekudrble TTL ProbeAudible Slow PuttiesLogic ProbeLogic Analyser

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SWITCHING

Touch Triggered &stableTouch Sensitive SwitchElectronic SwitchSound Operated 2 WaySPST Switch Flip FlopTwo Signals on one Wire

INDICATORS

Line -it -Light3 Step LevelLight LevelBargrapn DisplayFuse FailureBlown FuseBack Up LampDC Lamp FailureFM Tuner StationCurrent FlowDisco Cue

FLASHERS

Oanong LightsLow Frequency Strobetad-.

Ultra Swag.

POWER CONTROL

LOA Mains ControlFloodlamp ControlZero Crossing SyncTrain ControllerLow Ortlensntial Thermostatsimple Temperature ControlFull Wave SCR Control

AUTOMOBILE

Brake Lamp FailureCourtesy Light DelaySimple Huard LightL,ght Extender & ReminderFour Way FlasherHeadlamp DipperWooer OetaySuppressed Zero VoltmeterRev Counleol.horneterAuxiliary Battery

DETECTORS &COMPARATORS

Peal, Detects HoldWindow DetectorPeak Pr remPosdive PeakReaction Comparator

RADIO FREQUENCY

Cryfrat MarkerIDo one MarkerRF VoltmeterRF DetectorLED RF indicatorRF Amplifier Prot.OonPET -RadioOp -Amp Radio

MISCELLANEA

Phase Locked LoopTouch DoorbellPhase Lock ControlAudioVirtual Earth MixerProp EliminatorLoudspeaker ProtectionDON Capacitance ProbeDigital Tape Recorder AdaptorBreakdown Diode SubstitutionDual Function ChargerDual Mode AmpCapacitor SubstitutionEtectronic CapacitorSpeeding Up Darlington,Shutter SaverThyristor SensslivrtySound Operated FlashStrength TesterLogic No. Immunity

TIPS

Identifying 74 SeriesSupply PinsSoldering IC sTinning With Solder WickPCB StencilsFront Panel Fin.OIL DollingFluorescent StartingAvoiding insulted Heat SinksTTL Mains InterfaceBoost Your MainsHrgn Resistance on Low Wt..High Voltage ElectroldicsTransistor IdentificationTemplate & Heet Sink forPower Tr...torsTransistor SocketSolder Flow ProblemsOdd Resistor ValuesResistors in parallelCMOS OIL Handlingidentifying Surplus ICSExtending Battery LifeBattery SnapsPower Supply or BatteryBattery CheckingWick RemoverTransformers at reverseLoudspeaker CheckingImproving UJT LineantySignal TracerCrystal few..Cheep Vance.Zer. Lifts Cap... Rating

DATA

741 Op -Amp DataBC 107-109 DelaBC 177-179 DataCMOS & TTL Data2143055 D.IA12955 DateBipolar Data Tab.Bipolar FETe RectifiersDiod. Prnoute Zone, Misc

ALARMS

B urr. AlarmPhoto Intruder AlarmIntruder AlarmPhoto Electric RelayLow TemperatureiLights outTemperature SensorCoolant levelWater LevelElectromc LockCar Battery WatchdogSimple Car Ate.Simple Lock

AMPLIFIERSPREAMPLIFIERSHigh input impedanceH igh Impedance BullerLow Output ImpedanceKoh Input ImpedanceLow Frequency ExtenderVirtual Earth Preamp

LIT:feS'leelo TapePr.arnglayer2 5 Wad20 Watt Slaveto WattLour. icrophoneVoltage Controlled AmpWide Band Amok,.V.I. Power AmpBroadband Amp

SIGNAL PROCESSORS

Fury BoxGuilar Fu],Furl BoxWaa WaaDisco AutoledeSimple Autotadeinformation Trend.Optical Purse ConditionerTV Sound PickolfCr.klefree PotentiometerVoltage to FrequencySine to Square WavePrecision AC to DCVoltage ProcessorUniversal MeterDouble PrecisionFast Half We.Simple ChopperNo. Pc;vcting SCR TriggerPhase Shifter

SIGNAL GENERATORS

SimpleVariable Duty oweFast EdgeFET

VaImproved DMy cycStable CCheap 1CMOS)Simple TTL XTALUncrarcat OTALPulseZero CrossingSimple PulseNeedle PulseStable Linear SawtoothZenerNosePerak

Simple RelaxationTriangle with independent slopeE sporventielWderange MultivibratorMultiple Waveform

Uneat Sweet,Step Frequency

Simple SirenShip SirenTwo ToneToy Sirenso. Stan. Z CarsSound EffectsSound Effects

FILTERS

BandpassLow j firgh PassRefection NotchBandpassCartridge E0 dr RumbleHum StopperTape Hiss ReductionSimple Crossover

DIGITALThermometerHeads or TailsBinary CalculatorVoltmeterSeven Segment to °KernelRle

Random BinaryCMOS DieMullip.er HintsL C MemoryCMOS Clock

POWER SUPPLIES

ConstantTemperature StableConstantVottage ControlledPreoson Voltage Divide,Dual RolantySimple BalancedVol

Short Circuit Protect.Simple TTL Supply274414 SupplyStable ReferenceTrenstormerless Invert.,DC to DC ACVoltage MultiplierAutomobile ConvertorShaver AdaptorDC -DC.0 Voltage From BatteryVarAble re or ve outputSemple12v troth Battery ChargerBucket RegulatorAdjusting Zener VoltageVariable Zen.,Zener Bo sting of RegulatorsN igh PowerElectronic FuseBetter FuseRece,lator a fuseFes. 4,1.gSCRVoltage PutantyNI CAD DischargeCur rent Lan.ong

kococa

tl1/4 6e°\


ETI Project LCD Thermometer

LCD Thermometer

This simple yet accurate temperature meter will find many uses in thelaboratory or home. It utilizes the digital pane described in the February78 issue, details included here.

THE RELIABILITY OF electroniccircuits in the days of tubes was, tosay the least, poor by today's standards.The introduction of transistors andintegrated circuits increased reliabilitydramatically. One of the main reasonsfor this is the reduction of powerdissipation and the resultant loweringof temperature. Devices and circuits arenow designed to minimise powerdissipation as this allows a highercomponent density while increasingreliability. However some circuits bytheir nature must dissipate high powerand the semiconductor devices usedmust be kept within their temperaturelimits.

This temperature meter will allowtransistor temperatures to be measuredand the appropriate heatsink chosen.It is just as useful outside the electronicscene measuring liquid or gas tempera-ture especially where the readout needsto be physically separate from thesensor.

USE AND ACCURACYThe accuracy of the unit depends on thecalibration; provided it has beencalibrated around the temperature atwhich it will be used, accuracy of0.1 degree should be possible. We couldnot accurately check linearity but itappeared to be within 1 from 0 to100°C.

However other errors will affect thisreading. If measuring the surfacetemperature i.e. a heatsink temperature,there will be a temperature gradientbetween the surface and the junction of


eti 589

Temperaturemeter

31

Ell Project

the diode. Silicon grease should be usedto minimise the surface-to-surfacetemperature difference. Also whenmeasuring small objects, e.g. a TO -18transistor, the probe will actually coolthe device slightly. At high temperaturesthese effects could give an error of upto 5% (the reading in this case is lessthan the true value). If the probe isin a fluid, e.g. water or air this problemdoes not occur.

CONSTRUCTIONAssemble the panel meter as previouslydescribed but omitting the zener diodesand R6 and R7. The value of R1 hasalso been changed. The decimal pointdrive should be connected to the right-hand decimal point. The additionalcomponents can be assembled on a tagstrip as shown.

We mounted our unit on a tag strip asshown in the photo. While we have notgiven any details, knocking up a caseshould be no problem. For a powersupply we used eight penlight Nicadcells giving a 10V supply. If dry batteriesare used six penlight cells arerecommended although a 216 -type 9 Vtransistor battery will give about 300hours of operation.

The sensor should be mounted in aprobe as shown in Fig. 1 if other thanair temperature will be measured. Thisprovides the electrical insulation neededfor working in liquids etc. It should benoted however that the quick dryepoxies are not normally good near orabove 100°C and if higher temperaturesthan this are expected one of the slowdry epoxies should be used.

CALIBRATIONTo calibrate this unit two accuratelyknown temperatures are required, oneof which is preferably zero degrees andthe second in the area where the meterwill normally be used and highestaccuracy is required. For a general-purpose unit 100 C is suitable. Theeasiest way of obtaining these referencesis by heating or cooling a container ofdistilled water. However temperaturegradients can cause problems, especiallyat zero degrees.

One method of obtaining water atexactly zero degrees is to use a test tubeof distilled water in a flask of iced waterand allowing it to cool to near zero.Now by adding salt to the iced water itstemperature can be lowered to belowzero. If you are very careful, the testtube water will also drop below zerowithout freezing (you should be able toget to about -2 C). However the slightestdisturbance at this temperature willinstantly cause some of the water tofreeze and the remaining water to rise

SPECIFICATIONSTemperature range

Resolution

Sensor

Power consumption

- 50°C to +150°C- 60°F to +199.9°F

0.1°C or F

silicon diode

1.5mA @ 9 V dc

ADD PIECEOF INSULATIONBETWEEN LEADS

JOIN DIODE LEADSONTO WIRES

Fig. 1. This diagram showshow the sensor is mountedinto a ball-point pen casingor similar.

to exactly zero, providing an idealreference.

For a hot reference the boiling pointof distilled water is very close to 100 Cespecially if the container has a solidbase and is evenly heated e.g. on anelectric hotplate.

The actual calibration is done asfollows:

1. In the 0°C reference adjust RV2 andRV3 until the unit reads zero.

2. In the hot reference adjust RV1 togive the correct reading.

This should be all the adjustmentrequired.

If zero degrees is not available, e.g.if setting up for °F, the followingmethod can be used:1. In the cold reference use RV2 and

RV3 to adjust reading to zero.2. In the hot reference use RV1 to

adjust the reading to indicate thetemperature difference between thetwo standards. If freezing and boilingpoints are used,.this will be 180°F.

3. Now, back in the cold bath, adjustRV2 and RV3 to give the correctreading.No further adjustment should be

required.


LCD Thermometer

D11N4148.

(SENSOR)

R1110k

R1227k

RV22k

RV3200R

R135k6

RI10k

RV11k

R51M

Fig. 2. Circuit diagram of thecomplete temperature meter.

The printed circuit board forthis project is on page 97.

T 510n

470iC2

C3220n

- HOW IT WORKS TWhile the voltage across a silicon diode isnominally about 600 mV it is dependentupon the ambient temperature and currentin the C 'vice. The temperature coefficientis neoative, i.e. the voltage falls withincre sing temperature but fortunately islinear in the region of interest. The actualvalue varies with current and from deviceto device, but is typically -2.2 my/ C at250 µA.

By measuring the voltage across thediode with a suitable offset voltage tobalance the voltage at zero degrees anaccurate temperature meter results. Thedigital panel meter described in Feb. 78has a stable reference voltage available(between pins 1 and 32) of about 2.9 V;with the 10k resistor R11 this providesa constant current for DI (the sensor).The offset voltage is also derived from thisreference voltage by R12, RV2 and RV3.The panel meter is used as a differentialvoltmeter and measures the potentialdifference between the offset voltage andthe diode. We have used two trimpotsin series in the offset adjustment to givebetter resolution. If desired a 10 -turntrimpot can be used (2k2). Adjustment ofthe three potentiometers allows the meterto be calibrated in either °C or °F withthe upper limit of 199.9°F due to thepanel meter over -ranging.

The power supply is simply a 9 Vbattery, and so the zener diodes anddropping resistors described in the panelmeter article should be omitted.

R247k

_L C1100n

R9

ALL VOLTAGESARE REFERREDTO PIN 1. 21

(-4.9V) 3736 (-2.8V)

35 (-2.9V)

100k

R84M7

C610n

R104M7

2N3904

BACKPLANE

32

IC1 131 ICL7106 DECIMAL

POINT

30 (-4.8V) 2022

LCDDISPLAY

29

25

28

40 9VBATTERY

27 R3100k

34 (--2.8V 1 39 ,-/VVV-

C4100p

NOTES:*THESE POINTS CANNOT BE

33 (-2.9V ") 38 MEASURED WITHOUT AFFECTINGOPERATION EXCEPT BY A VERY

26 (-9.6V) HIGH IMPEDANCE ( > 1 G12 )

VOLTMETER.


ETI Project LCD Thermometer

9V BATTERY

TAGSTRIP

SOCKET TOPROBE(SENSOR)

Fig. 3. The external components associatedwith the panel meter. For more details of thepanel meter see February 78 ETI.

eti 589

Temperaturemeter

0 0PROBE POWER

PCBs for this project areavailable from: B & R Ele-ctronics, P. 0. Box 6326F,Hamilton Ont., L9C 6L9,and Spectrum Electronics,38, Audubon St. S.,Hamilton, Ont., L8J 1J7.Kits of parts and boardsare available fromNorthern Bear Electronics,P. 0. Box 7260, SaskatoonSask., S7K 4J2.

PARTS LIST

RESISTORS all W, 5%t R1 10k R2 47k R3 100k

R4 not used"R5 1M

R6 not usedR7 not usedR8 4M7R9 100kR10 4M7R11 10kR12 27kR13 5k6

,'OTENTIOMETERS RV1 1k 10 turn trim

RV2 2k trimRV3 200 trim

,APACITORSCl 100n polyesterC2 470n "

" C3 220n " C4 100p ceramic

C5 10n polyesterC6 10n "

SEMICONDUCTORS IC1 ICL7106

Q1 2N3904D1 1N4148

MISCELLANEOUSPC board ETI 135Tag strip

LCD Display Socket for LCD display

BoxSwitch9V battery

These components are supplied withthe Intersil ICL7106 EV evaluation kit.

t This value has been changed fromthe original panel meter.

r 1

DECIMAL,POINTDRIVE

443k.ZD2 ZD1

HIGH LOW(COMMON)

INPUTSFig. 4. The component overlay of the panel meter with the displayremoved. Note that for this project R4, 6, 7, ZD1, 2 and the externalleads are not used.


INTRODUCINGCOMPUCOLOR IIThe Compucolor IIis a disk basedmicrocomputer sys-tem for businessand personal use.

13" COLOR MONITOR 17K R.O.M. 8K R.A.M. (16 & 32 AVAILABLE) COLOUR GRAPHICS BASIC FULL SIZE KEYBOARD FLOPPY DISK RS232 INTERFACE MUCH, MUCH MORE

JUST $2250.00MAIL ORDERS: Ont. Residents add7% Prov. Tax. F.O.B. Toronto. Pleasespecify shipping method desired.

COME IN AND SEE USFULL SERVICE DEPARTMENT

COMPLETE SELECTION OF BUSINESSSYSTEMS AND SOFTWARE IN STOCK.

OPEN Thus. & Fri. Til 9:00 p.m.

HOUSE oF EDITTLITERS368 EGLINTON AVE. W.,

TORONTO, ONT. M5N 1A2lit

(416)482-4336 (AT AVENUE RD.)

111.1.1A

SOMPUTERPE CIA LISTS

a division of comspec communications inc.

PET -8K $1050 upSORCERER from $1295APPLE from $1637SDSystems call for quoteKIM -1 $249

**VISIT OUR STORE**

WE ALSO HAVE

-Books-Supplies-Information-Technicians-Experienced Staff-Consultants

Send orders with cheque, Money Order,Chargex or Master Charge. Includeexpiry date. COD orders must include25% of order. Allow for bank clearance.All shipping collect. Ont. Res. add 7%PST.

COMPUTER SPECIALISTS944 Wilson Ave.

Downsview, Ontario M3K 1 E7(416) 638-4477

ETI Computer Catalogue

INTRO

This sixteen -page supplement to ETI June 1979 givesyou a picture of eleven personal computers. See theprevious page for a list of contents and page numbers.

This supplement gives brief detailsof some 8 -bit microcomputersavailable in Canada. We have edit-ed the manufacturers' literature togive you a single -glance view ofthe important specs.

There are some famous namesnot included - this is because welimited our coverage to thoseproducts visibly being sold here,by manufacturers, representatives,or dealers who were easily access-ible and co-operative. (Our theorywas that if we have to go to someeffort to get information, ourreaders might have to go to a lotof effort to get the product.) Evenso you might have trouble gettinginformation out of some of thecompanies mentioned. So we haveincluded the phone numbers ofUS manufacturers for some prod-ucts.

This 'catalogue' is a simpleoverview to give you a quickpicture of what's available. Moredetails of all these products areavailable from manufacturers'literature. Make sure you lookdeeper into the specs and try outa few machines before buying.

So here you can see what'savailable; the other half of yourbuyer -research is to define whatyour needs are. Ask if the comp-uter you have in mind can be ex-panded into a more sophisticatedsystem than you need today.

Take a look at the computermagazines and ask if you will oneday want to add-on to your com-puter the products you see advert-

ised there. The most commonstandard for add-on boards isS100, but the big manufacturerswith non-standard buses makeavailable a range of boards wideenough to cater for most people.

To save money look at buyingthe minimum system and expand-ing it yourself with cheap boardsand peripherals. For instance,S100 RAM cards are availableat prices below those shown inthese pages. Rather than buyingyour disk drive from the companywho made your computer, checkout other companies (one of themwill be supplying your computercompany, anyway).

Note that boards have to haveslots to plug into, with bufferedinterfacing and power supply.Note that disk systems, printers,etc, need software.

Not all the computers comewith the beginner's language,BASIC. Not all have 'assembler'programs available, or the facilityof machine -language programm-ing (these are used by people whoare developing programs for dedi-cated computers).

To learn more about computersread the series Bits, Bytes andBauds in these back -issues of ETI:Sep, Nov, Dec 77, Jan, Feb, Mar78. Learn more about micropro-cessors by reading the Microbio-graphy series in these back issues:Oct 77 (4004. 8008), Nov 77(8085, Z-80), Dec 77 (6800,6805), Jan 78 (1802), and Mar78 (2650).


Made by Rockwell Intl,Microelectronic Devices,

(D/727-ETI), PO Box3699, Anaheim, CA 92803.

Phone 714-632-3729.

Available from Hamilton-Avnet in Toronto, Montreal,

and Ottawa.

SAMPLE SYSTEMComputer with 4K RAM -

AIM 65-400 $599Assembler ROM $127.50BASIC ROM $150Power Supply -

(Not Rockwell) $100Total for this system -

approx $980

c' 0 -CF4F4PPC R TITSPz_RY

- Sample System


AIM65

The AIM 65 is the only computer in thissupplement which comes without case orpower -supply. But this is a pretty unusualproduct in other ways, too. Unlike thetypical microprocessor evaluation boardsthis one has a full terminal -style keyboard,better than you get on many fully -pack-aged computers. And there's an on -boardprinter. And the full 64 ASCII font can bedisplayed on the 20 -character 16 -segmentalphanumeric display.

The keyboard has 54 keys to provide70 functions (26 alpha, 10 numeric, 22special characters, 9 control and 3 user -defined functions).

The thermal printer prints the 64 char-acter ASCII set in a 5x7 dot matrix at therate of 120 lines per minute with 20 char-acters on each line.

Two 4K ROMs are installed, and threespare sockets are available for another 12K.The monitor program gives the computerits name (Advanced Interactive Monitor),and allows the user to: enter and editprograms directly, no opcodes to mem-orise; list programs on the printer or TTY;display/alter registers or memory; setbreakpoints, trace and debug programexecution; control the printer; transfer infoto/from cassette or TTY; execute programsin on -board or external RAM, ROM, orPROM; interface the assembler and BASICinterpreter.

The spare ROM sockets are filled if you- Upgrades

buy the optional assembler (4K) and opt-ional Microsoft BASIC interpreter (8K).

The processor is Rockwell's R6502,which has 65K addressability and a 56 -command instruction set. The AIM 65comes in two sizes - with 4K RAM or1K PAM ($100 cheaper).

The board has two R6522 VersatileInterface Adapter chips (one handles theprinter, TTY and cassette interfaces, theother is all for you). Each has two paralleland one serial 8 -bit bidirectionalI/O ports, two 2 -bit peripheral handshakecontrol lines, and two 16 -bit interval -timer/event -counters. Also on -board is an R6532RAM -I/O -Timer - a multipurpose chip.

Interfacing is provided for TTY (20 mAcurrent loop) and two cassette machines(with choice of two formats). These inter-faces are available at a 44 -pin applicationconnector along with connections to theuser's VIA ports (see block diagram).Another 44 -pin connector brings out theaddress, data, and control lines for anyexpansion you might dream up.

It's hard to see in the photograph butthere are actually two boards - the key-board module is 12x4in, the circuit moduleis 12x1Oin, and detachable.

All this is yours if you can rig up apower supply to provide +5V at 2A (max),regulated to +/-5%, and +24V at 21/2A(peak, 0.5A average), unregulated(+/-75%).

The only AIM 65 upgrades are the two ROMs we have included in our Sample System.The user can expand the system using the I/O ports or bus expansion.



SAMPLE SYSTEMCat.No. Price

Apple II with 16K RAM -A2S0016 $2200

RF Modulator -(Not Apple) $50

Cassette Recorder -(Not Apple) $100

Colour TV -(Not Apple) $600

System Price (if you do notbuy a new TV) about $2350

Sample SystemApart from the monitor (or TV plusmodulator) and cassette recorder, theApple II is a complete computer. The 8KROM holds BASIC (6K) as well as thesystem monitor. The single board canhold up to 48K of RAM (using 16K ICs).The processor is the 6502. Power supply,keyboard, cassette interface and game I/Ocome in the standard package. Also inc-luded are two game controls, manual,BASIC manual, and video display circuitry.

The display can be text, high resolutiongraphics or colour graphics. Two pages ofgraphics memory are selectable, and thebottom four lines of the display can beused for text. Graphics resolution (four-colour: black, white, violet, green) is280x192 (or 280x160 with text at thebottom of the screen). 8K bytes of RAMare displayed.

Resolution in the 15 -colour mode is40x48 or 40x40 with four lines of text.

Upper-case text is shown as 24 linesof 40 characters (normal, reversed or flash-ing).

Standard I/O is cassette interface, gameinterface, and buffered connectors for 8

expansion boards. Cassette interface is at1500 bps. Game I/O handles four paddleinputs, three TTL inputs, and four TTLoutputs.

Apple BASIC is a translated integerBASIC which includes: any -length variablenames; immediate indication of syntax orrange errors; multiple statements on oneline; integers from + to - 32767; stringarrays to 255 characters; single-dimentioninteger arrays; graphics commands to drawpoints, horizontal or vertical lines, to assignor read colours; game paddle read function;set display to text/graphics; memoryboundary adjust; break execution & cont-inue; line number and variable tracing fordebugging; PEEK, POKE, and CALL;cassette SAVE and LOAD; automatic linenumber mode; RND, SGN, ASC, LEN,and ABS; return stack POP; GOTO andGOSUB; fully interruptable.

The 16K version (and 32K & 48K ver-sions) include Applesoft BASIC on tape,with documentation.

With 32K of RAM add $200, with 48Kadd $400.

APPLE 11

Made by Apple Computer,10260 Bandley Drive,

Cupertino, CA 95014.Phone 408-996-1010.

Available from Compucentre,Compumart, Cesco, and

various others.

UpgradesExpansion Boards:Apple makes a range of plug-inboards to fill the 8 slots avail-able on the main board. Notethat S100 boards do not pluginto the Apple II.

For $265 you can get a parallelinterface board designed for usewith a printer (board A2B0002).

The A2B0007 is a printer inter-face card for use with Centronicsmatrix printers; it costs about$300.

The A2B0003 is an RS -232Cserial interface card for interfacingwith other computers either dir-ectly or via a modem. It costs$265.

A2B0005 is a high-speed serialinterface card (RS -232C) for$290.

A2B0001 is a double -sided23/4x7in prototyping card for $35.

A2B0009 is an expanded ver-sion of Microsoft's BASIC; thisplug-in ROM card costs $300.

A new addition to the range isthe A2M0024 one-year calendar -

clock with 1/1000th second acc-uracy.

Peripherals:Apple sells a range of productsto expand your system - diskdrives, printers, etc. Coming soonis a graphics input tablet with alinear resolution of 200 pts perinch over an 11x11in area.

Software:The $37 A2M0022 cassette con-tains the Dow Jones stock quotereporter package. Also available isthe usual range of game andcheckbook programs.


0 (11

Sample System

td440;5;(itPo( GM. MD I* 116110,111117 F11119111311Fi01

1 MOW as- MO TOM CJI MARCIE

t V910547.114411914,140(4 -


COMPUCOLOR ll

Made by Compucolor Corp.,PO Box 569, Norcross,

GA 30071.Phone 404-449-5996.

Available from House OfComputers and Datamex in

Toronto, Computer Shop inWinnipeg, and KerridaleCompute -Micro in Van.

-couver

SAMPLE SYSTEMComplete System -

Model 5

Above: Compucolor realise that to sell lots ofcomputers they have to provide you with astrategy for getting the wife's approval. Whatbetter than telling her you bought it for herto help her remember recipes. Left: The diskslot doesn't show in the photo so here's a d, -awing.Below that are a couple of screen shots - butthe colour displays don't show up well in ETI.Right: These are the two upgraded keyboards.

The Compucolor II is a complete computersystem with 72 -key keyboard, built-incolour video monitor, and built-in floppydisk facility. The Model 5 comes with 32Kof RAM. The model 4 has 16K for $2550.

The processor is the 8080A. 16K ofROM holds Disk BASIC, CRT controlfirmware, and the File Control System.Sockets are included for an additional 8Kof ROM.

There is one RS -232 serial interfaceavailable. Expansion- is possible usingthe 50 -pin bus.

The CRT displays 64 characters on 32lines in 8 colours and 2 character sizes.The graphics display resolution is 128x128,with vector -generating software. The fullfont contains 64 ASCII characters and 64graphics characters. In the Terminal modethe computer can be used for time-sharingvia a RS232C interface.

The terminal commands control Page/Roll Mode, Erase Line, Erase Page, Tab,Character Size, Blink, Cursor Home,C -Left, C -Right, C -Up, C -Down, X -Yaddressing for cursor, Caps Lock, CPUReset, Colour Selection, 15 plot modesBlind Cursor, Local- Full- and Half -Duplex,Write Vertical Mode, and TransmitCursor and Page Modes.

3 3 43 4 s:,, 3433 ,

$2995

Stored in ROM is the 'Disk BASIC8001' interpreter which uses 29 state-men.:s, 3 commands, 19 mathematicalfunctions, 9 string functions, and 12 diskfile commands.

The disk storage system puts 51.2Kbytes on each side of a 514in diskette.Average access time is 200ms; transferrate is 76.8 kilobits/second.

Optional extras include two deluxekeyboards: the CCN keyboard has colourcluster and number pad (101keys) for$225. The CCNF keyboard adds another16 function keys for $335.

Another disk drive will cost you $599.If you buy Model 3 or 4 you can add 16Kof RAM for $570.

The following diskettes are available for$30, many of the game diskettes haveseveral programs on them: Hangman,Othello, Math Tutor, Chess, Star Trek,Blackjack, Cubic Tic-Tac-Toe, PersonalFinance Vol 1, Personal Finance Vol 2,Bonds and Securities, and Equity.

Also available on diskette are anAssembler ($37.50), a Text Editor($37.50), and Personal Data Base ($45).

The computer comes with a Samplerdiskette.


The H8 computer.

-Sample System


Made by Heath Company,1478 Dundas St E, Missis-sauga, Ontario, L4X2R7.

Phone 416-277-3191.

Available from HeathkitElectronic Centres in Missis-sauga, Montreal, Edmonton,Winnipeg, Ottawa and Van-

couver.

The H8 chassis holds the Heath 50 -line buswith slots for nine cards. It comes witha ready -wired 8080A CPU card with sevenvectored interrupts available. Also supp-lied is the Front Panel memory card whichinterfaces to a 16 -key pad and nine -digitLED display for octal programming. Thekeypad gives direct access to registersand memory, one -button program loadand dump, and input/output keys fordirect communication with any port. Thedisplay shows contents and location ofmemory, registers or I/O ports - andupdates continuously even when theprogram is running.

WH8-16These 16K RAM cards come ready wiredto enable you to expand the memory up tothe 8080's addressing limit of 65K.

H8-5:This card provides serial I/O for videoterminals, printers, etc. Provides 20 mAcurrent loop and RS -232 levels. Also hasa cassette interface which can controltwo machines. Available in assembed formfor $250.

H9:This video terminal uses a 12in CRT to dis-play twelve lines of 80 characters. Input isvia the 67 -key keyboard. Display is upper-case only, and can be organised as fourcolumns (each 12 lines of 20 characters).Serial interfacing is via 20 mA currentloop, RS232C, or standard TTL levels.

Parallel interfacing uses TTL levels on8 bits input and 8 bits output, with hand-shaking lines for connection to paper tapereader/punch. Simplified kit has wired andtested control board and wiring harnessfitted with connectors.

H17:This package includes a disk controllercard for the H8, and disk drive with powersupply. One drive is included - a secondone costs another $580, Storage is on hard-

sectored 40 -track 5%in diskettes, eachholding 102K bytes. Typical random sectoraccess times are less than 250 ms; track -

step time is 30 ms maximum. The priceincludes a blank diskette. At least 16Kof RAM should be fitted to the H8.

Fully assembled the H17 costs $1030.

H8-17:To use the disk system you need this oper-ating software. It includes Benton HarborBASIC (if you want Microsoft BASIC youhave to spend another $125 on the H8-21diskette), a two -pass absolute assembler,a text editor and console debugger, and thedisk utility programs.

Extended Benton Harbor BASIC hand-les strings and files, and supports the.WH-14 line printer and WH8-4 interfaceboard.

5% Discount:If you buy the H8, a major peripheral,and the memory, software and accessoriesyou need, Heathkit will give you 5%discount.

H8


Chassis, PSU, CPU Board,& Front Panel -

H8(Kit) $530Two 16K RAM Cards -

WH8-16(Wired) $700WH8-16(Wired) $700

Serial Interface Board -H8-5(Kit) $190

Video Terminal -H9(Kit) $1000

Disk Drive & Controller -H17(Kit) $900

DOS Software on Disk -H8-17 $125

All The Above With 5%Discount $3938

- UpgradesPlug-in Boards:The WH8-16 and H8-5 are des-cribed in the sample system.Other boards are:

H8-1 is an 8K memory cardsupplied with 4K of 4K -bit staticstatic chips for $200 (kit).Thechips for the other 4K cost $140.

The WH8-8 is a an assembled8K board for $420.

The H8-2 is a parallel interfacecard with three independent portsand handshaking. Price for kit is$230.

WH8-4 is an assembled serialI/O card for $420.

The H8-7 is a breadboard cardfor $$150, with bus interface andaddress decode.

Cables are needed to connectperipherals to the H8-4 and theH8-5. These are $30 each.

Other Accessories:The H14 is a new line printer for$800 in kit form ($1300 assemb-led). The H36 is an LA36 DECWriter II for $2195. The H10 isa paper -tape reader/punch for$580 (kit) .

Heath offer a self -instructionprogramme for learning BASIC.You get a workbook with a Black-jack program listing, and referencecards. Price $60.

If you have 40K of memoryand floppy disk you can spend$150 on a Microsoft FORTRANinterpreter.


Below: The H9 video terminal. Top Right: The new H14 line printer.Bottom Right: The H8-17 mini disk drive.

LOW COST INTERACT MICROCOMPUTERNow available in Canada a powerful microcomputer, costing severalhundred dollars less than other similar microcomputers currently onthe market. The Interact is a full function microcomputer with"Advanced BASIC" programming capability. Simply attach to your

Mail to:

MARKETRON CORP. LTD.1240 Bay Street MallToronto, Ont. M5R 2A7Phone 416/923-1917Dealer inquiries invited!Dealership information availableto qualified retailers. Pleaserequest on company letterhead.

home television and you are on your way to becoming a computerprogrammer. Write your own programs or take advantage of themany Interact programs available from us on cassette. Futureoptions will include floppy disk and printer attachments.

Features include: full colour; sound;full size keyboard; built-in cassettedrive; 16K RAM - 2K ROM; includesRIF connector and two joysticks.Weighs only 12 pounds.

ONLY $ 79500

BONUS OFFERFor a limited time only receive 13program tapes ($300 value) includingEDU-BASIC, for only $50.00. Opt-ional Level II BASIC $39.95, MicroChess $29.95; plus many moreprograms available - complete listavailable upon request. Available atour store or by mail order.

Pls send: Cheque Money Order Chargex Master Charge American Express

ORDER INFORMATION

Interact MicrocomputerBonus Programs($300 value)

Ontario Res. add 7% sales taxShipping chargesTotal enclosed

$795.0050.00

$845.0059.15$5.00

$909.15

Card No Expires

SignatureName

Street

Town Province

Postal Code Phone

Other programs, add appropriate amount and 7% sales tax (Ont. Res.)


SAMPLE SYSTEMInteract Family Computerwith 16K RAM $795Level II BASIC on cassette -

US price $50(Colour TV also needed)

Sample System

The Interact Family Computer is designedas a computer -based compendium of videogames that doubles as an inexpensivepersonal computer. Program cassette playeris built-in, alongside a full 53 -key key-board, and the output is TV RF modulatedwith sound and 8 -colour video. Alsoincluded are two game controls - x -yjoysticks with hit buttons - and antennaswitcher.

The model 1 Interact used 8K of RAM;the 16K version is new and can handle theenhanced cassette BASIC. This allowslogs and trig and handles string variables.

The processor is an 8080A running at2MHz, with the monitor in 2K of ROM.

Currently there are five series of prog-ram tapes available. The 'Strategy' seriescomprises Blackjack, Star Track, Concen-tration, Chess Master, Video Chess, andInteract Micro Chess.

The 'Educational' series comprises AddEm Up, Compute -A -Color, Hangman.


Knockdown, Edu-BASIC (Level l), andMusic Maestro. Music Maestro comes witha keyboard overlay to give you a three -octave keyboard of black and white notes,plus vibrato. The computer will transposekey, allow you to edit your tune, and itdisplays a staff on the TV screen withkey signature and time at the beginning.

The 'Action' series is made up ofRegatta, Trailblazers, Dogfight, Show-down, Computer Maze, and Breakthrough.

The only program so far in the 'Life-style' series is Biorhythm.

The programs in the 'Management'series are Checkbook, Data Base Manager,and Financial Calculator.

Programs promised are Backgammon,Computer Football, Bridge Bidding, Scient-ific Calculator, and Computer Flashcards.

Interact Electronics promise also tomake an RS -232 interface, ROM BASIC,and disk storage available soon.

INTERACT

Made by Interact Electronics,PO Box 8140, Ann Arbor,

Michigan 48107.Phone 313-973-0120..

Available from ComputerWorkshops in Toronto,

and Focus Scientific inOttawa.


Sample System


The PET 2001-16/32 with newkeyboard. The inset shows the2021 electrostatic printer.

PET Models:There still PETs available withthe built-in cassette: this is the8K PET which sells for $1095.The high -quality keyboard PETsare the 16K and 32K versions for$1495 and $1795.

2001-16K:This model is similar to the PET we re-viewed in our February 1978 issue, but hasmore RAM and in place of the old key-board and built-in cassette you get a pro-fessional keyboard (and number pad).The 14K bytes of ROM hold the BASICinterpreter (8K+), the operating system(4K), and the monitor (1K). The videodisplay is built-in: you get 40x25 charac-ters on a 9in CRT. In addition to the 64ASCII characters there are 64 graphicscharacters available.

The BASIC handles strings, integers,and multiple-dimention arrays, uses nine -digit precision, and PEEK and POKE fordirect memory access. Sockets are availablefor another 8K of ROM; ROMs for theassembler or disk controller plug into the

main board.Input/output is provided via the IEEE

488 instrument interface, or via the mem-ory -mapped user port.

C2N:This external cassette recorder/player hasbeen modified by Commodore for highreliabil.ty. The PET can interface twincassettes to handle and update files.

2021:This electrostatic printer uses only fourmoving parts to print all the 128 PETcharacters (upper and lower case letters,numbers and graphics) onto aluminium -coated paper. It connects to the PET userport (Parallel data at TTL levels) or theIEEE port. Speed is 150 Vines per minute.

2041The PET single mini disk drive uses aShugart SA390 (for 514in diskettes). Thedisk operating system comes in two ROMswhich plug directly into the main PETboard, plus a ROM which replaces one onthe board. The interface is made directly tcthe memory bus of the PET.

PET

Made by Commodore Busi-ness Machines, 3370 Phar-macy Avenue, Agincourt,

Ontario, M1W 7K4.Phone 416-499-4292.

Available from the dealersmarked in the Dealer List

on page 49.

SAMPLE SYSTEMCat. No Price

Computer with 16K RAM -2001-16K $1495

Single cassette recorder -C2N $120

Electrostatic Printer -2021 $695

Single Disk Drive -2041 around $775

Total For All Above -around $3085

- Upgrades

Peripherals:The best way to find out what ishappening with PET peripheralsis to see what you local dealerhas in stock. These are rumouredto be appearing soon under thePET label: 2022, a tractor -feedprinter for $1295; 2023, a dot-matrix printer for $1095; andmaybe some of the productsadvertised now in the US com-puter magazines.

Boards:Sorry, we can't help you muchhere. Companies do make boardsfor interfacing with the PET,including an S100 expansionboard. But as far as what'shappening in Canada try contact-ing your local dealer - or godirect to a US company when yousee their ads.

STOP PRESSLatest news is that this

product will not be available.We also have heard that the2020 dot-matrix printer is

also unavailable.


Sample System


Sol -20/32:The Sol comes in two simple versions -the Sol -20/16 (16K RAM and 5 free slotsin the S100 backplane) for $3115, and theSol -20/32 which is carries an extra 16KRAM card.

The Sol uses the 8080A and an operat-ing system called Solus which comes in a'personality module' for use with thedisk system the Solus ' personality module'is replaced by the Bootload module.This replaces the terminal functions ofSolus with the Disk Operating System.

You can connect an audio cassetterecorder directly to the Sol, and use theBASIC/5 cassette which is included. TheSol is capable of controlling two cassettemachines.

There is an extended BASIC availableon cassette or disk. Other languages avail-able are FOCAL, FORTRAN, and PILOT.(PILOT has been developed for PT foreducational applications.)

Built into the Sol is an 85 -key capacitivekeyboard with cursor keys and arithmetickeypad.

Video is provided to display 16 lines of

64 characters on a monitor (or TV plusmodulator). The character set comprises96 ASCII upper and lower case charactersplus 32 optionally -displayable controlcharacters. The cursor features switch -selectable blinking.

I/O is via an RS-232/20mA loop serialinterface, or an 8 -bits input + 8 -bits outputTTL-level parallel interface.

Video Monitor:Processor Technology feature in their liter-ature a modified Panasonic TV set for useas a video monitor. This wasn't availablewhen we checked in Toronto, but the storedid have a monitor of another make,. Asvideo levels are pretty standard it shouldbe no problem to make the Sol work withany monitor (or any TV set, with a bitof work).

Helios II:The Helios II Model 2 is a dual -drivemachine; the Model 4 has two dual -drives.These make available 750K and 1500Kbytes of disk memory.

SOL

Made by Processor Tech-nology Corp., 7100 JohnsonIndustrial Drive, Pleasanton,

CA 94566.Phone 415-829-2600

Available from ComputerMart in Toronto, Computer

Ciruit in London, andBasic Computer Group in

Vancouver.


Sol 20 with 32K RAM -So120/32 $3560

Video Monitor -(anybody's) $400

Disk System -Helios II Model 2 $4960

Total for above $892044


Sample System


C..140Nuerders

N

-'Shers..

Cartridge/ N

SORCERER

2 MaeOapno

Block DiagramSorcerer Computer

Standard EquipmentOptional Equipment

Sorcerer:The Sorcerer is a Z-80 based computer thatcomes with 8K or more RAM and has a 79key keyboard built-in. The keyboardincludes separate number/cursor pad.Video output displays 30 lines of 64 upper -or lower-case characters using the fullASCII set (128). Additionally 128 graphicscharacters are displayable (either 64standard plus 64 user -defined, or alluser -defined).

The 4K ROM monitor program handscontrol over to a plug-in ROM -PAC.This ROM card comes housed in a caseidentical to that of an 8 -track audiocartridge - for quick language changing.Included in the basic price of the Sorcereris a ROM -PAC cartridge containing an 8KMicrosoft BASIC interpreter. Coming soonare ROM -PACs for APL, PILOT, DOS(Fortran, Cobol), and assembly language.

The standard BASIC allows multiplestatements per line, string manipulation,and multiple dimention arrays. In onesecond you can execute approx 700floating-point additions with seven decimal

digits of accuracy.Dual cassette interface is provided with

optional high/low speed to suit the qualityof your machine. Parallel (8 -bit) and serial(RS -232, 300 or 1200 baud) interfaces arealso provided.

Programs available on cassette includethe following titles:Casino, Personal Phys-ician (?!), Personal Data Management,Mangement Aids, Computer Aided Instruc-tion, Advanced Engineering.

Memory:On the main board are sockets for 32K ofRAM. You can buy a 32K Sorcerer for$1945 but you will probably save bybuying a cheaper model and fitting theextra RAM yourself.Expansion Box:A six -slot S100 expansion box is available.Although we don't make use of it in our'sample system' this accessory will benecessary for anyone wanting to addlots more memory, disk storage, or thefun S100 boards advertised in the comput-er magazines.

IU

I

111.1.Cenbel

z

Made by Exidy Inc, 969W Maude Ave, Sunnyvale,

CA 94086.Phone 408-736-2110.

Available from ComputerPlace and Comspec n Tor-

onto, Computer Innovationsin Ottawa, and Orthon in

Edmonton.

SAMPLE SYSTEMSorcerer with 16K RAM -

$1645Another 16K of RAM

chips - $250Expansion Box -

$425Single cassette recorder -

(anybody's) $100Video Monitor -

(anybody's) $400Price of this system -

approx $2820

UpgradesThanks to the S100 bus expansionbox there is a large range of plug-in boards available for the Sor-cerer. Using the interfaces pro-vided there is no problem conn-ecting any standard peripherals tothis computer.


UpgradesStandard peripheral interfaces areavailable at the expansion unit.This means it is easy to addprinters, disk systems, modems,etc. Four diskette drives can beadded, the last three costing $799each.

Radio Shack have a line printerfor $1899/$1999, tractor feedoptional. Top speed is 21 linesof 132 characters in one minute.Note Level II or disk BASIC isneeded to control these printers.

To communicate with ter-minals and other computersthe TRS-80 Expansion Inter-face has an optional Serial Inter-face board. This provides RS-232C signals.

There is a TRS-80 telephoneinterface which plugs into theRS -232 board and cradles a

telephone handset. It operatesin the 'originate and receive'mode and can provide two-waycommunication with anothercomputer with 'originate andanswer' capabilities.

The RS -232 board costs $170and the telephone interface is

$339.New items in the TRS-80 range

are: retrofit 12 -key numeric pad,$130; voice synthesiser, $589;business desk and printer stand,$299 and $150; and a technicalreference manual for $15,95.Software:A $55 Microsoft editor/assembleris available on cassette for anyone

with 16K of RAM. It creates bothsource and object files. It does

not support macros and con-ditional assembly.

A T -bug program allows you toprogram in machine language on aLevel I machine for $30.

Other cassettes come with theusual range of programs from $8to $50.

Sample System


The TRS-80 CPU,the expansion in-terface (underthe monitor),and the 'QuickPrinter'. Pluscassette recorderand Radio Shackvideo monitor.

Also in ourSample Systemis the mini disksystem.

TRS-80Made by Radio Shack,Bayview Drive, Barrie,

Ontario, L4M 4W5.Phone 705-728-6242.

Available from any of the700+ Radio Shack outlets

across Canada.

SAMPLE SYSTEMCat. No. Price

16K CPU with Level II -26-1006 ($1247)

Video Monitor -26-1201 ($299)

Cassette Recorder -14-841 ($69.95)

Package Price On AboveThree $1547

Expansion interface -26-1140 $4,9

Disk Drive & Cable -26-1160 $829

Quick Printer & Cable -26-8160&26-1401 $868.95

Package Price On All TheAbove $3692

26-1006:In ETI April 1978 we reviewed the simpl-est TRS-80 system, with 4K of RAM andLevel I BASIC (this system costs $899 withmonitor and cassette recorder). Spendingan extra $648 furnishes the CPU boardwith 16K of RAM and the vastly -improvedLevel II BASIC (using 12K of ROM, ratherthan 4K).

26-1201 & 14-841:The CPU board can interface directly withany standard video monitor (note: it doesnot work directly into a TV set; if youwant to use your set you have to buya video modulator or modify the TV forvideo input). Similarly any quality audiocassette recorder with remote control canbe used to store programs or data. Thetwo products in our Sample System arethe ones recommended by the manufact-urer.

26-1140:The CPU board cannot interface directlywith disks, printers, and other peripherals,and the board is limited to 16K of RAM.By adding the Expansion Interface you cancontrol up to four mini disk drives, a

printer (via a standard Centronics parallelport), and a dual cassette recorder. An

extra 16K or 32K of RAM can be fitted,and an RS -232-C interface board is avail-able. The Expansion Interface is a separatemodule with its own separate powersupply.

26-1160:The TRS-80 mini disk system uses 51/4 -inchdiskettes to provide 55,000 to 310,000bytes of on-line storage. With just one diskdrive you get about 55K of storage - thefirst diskette holds TRSDOS (Disk Operat-ing System) and Disk BASIC (which useabout 4.2K and 5.8K of RAM). The formatis 35 tracks of 10 sectors with 1/4K bytesin each sector. Average track access timeis 200 ms; it takes 600 ms to cross alltracks.

26-8160:The Quick Printer gives 150 lines/minuteon a roll of 4% inch wide aluminum -

finish paper. The printer gives upperand lower-case letters and all keyboardcharacters except arrows. All Level IIprinter commands are used. Three charac-ter sizes are available, giving 20, 40 or 80characters per line, software selectable.Level II and the Expansion Interfaceare necessary, so is the $69.95 cable(26-1401).


Sample System


Above : The VP -550 two -channelsound board. Left: The VIP hookedup to monitor and cassette.

Eastern Canada: RCA,1 Vulcan St, Rexdale,

Ont, M9W 1 L3.Phone 416-274-5491.

Available from Home Com-puter Centre in Toronto,

Wackid in Ottawa, andOrion in Kichener.

VIPThe VIP is a hobbyist computer designedspecifically for progamming graphics. TheCOSMAC 1802 processor is used with a512 -byte monitor program in ROM and2K of RAM. Sockets enable the RAM tobe doubled.

The 1802 has 16 16 -bit general purposeregisters, an 8 -bit D register and three 4 -bitregisters (that can be set under programcontrol), and features easy DMA oper-ations.

The CHIP -8 interpretive language is saidto be very easy to use (we haven't tried outthe VIP at ETI, yet). CHIP -8 allows 16one -byte variables and is limited to theoperations +, -, AND, and OR. In all thereare 31 4 -digit -hex instructions. Singleinstructions generate a random byte,read in a keypad digit, display a pattern,sound a tone or increment a variable.Subroutine nesting and machine languageinserts are permitted.

The firmware bit -maps a 256 -bytepage of memory onto the screen of themonitor (which you provide). A '1' inmemory makes a patch appear on thescreen, in any of 64 positions in anyof 32 rows. Alternate interrupt routinescan display up to 128 rows.

Software allows patterns (letters, num-erals, cowboys, etc) to be formed andmoved around the screen.

The keyboard is a 16 -key pad markedin hex with the bottom four keys doubling

as function keys - for the only four funct-ions available, memory write, memoryread, tape write, and tape read.

Interfacing is avaiable via two connec-tors. One provides 8 -bits parallel input and8 -bits parallel output, plus control lines,with 2 TTL load drive capability. Theother connector brings out address, data,and control lines, for expansion. Alsoprovided are separate sync and videosignals. There is no buffering, though. Thecassette audio and motor control leads, andthe video lead, are attached to the boardand fitted with plugs.

The power supply gives only 600 mAat 5V - but there are pc board pads avail-able for fitting a 7805 -type regulator andfilter capacitor (so you can add your ownunregulated power -supply).

The VIP comes with a cassette inter-face. A fixed -frequency tone sounds whilea tape is written, and also when keys aredepressed. An LED lights up to show whena tape has been read.

An instruction and maintenance manualis included. Featured in the manual are 20video game programs to get you started.

VP -590 & VP580:The first of these is a board which plugsinto the VIP and allows program control of8 colours. Any of four background colourscan be selected. The board has sockets fortwo auxiliary 16 -key keypads (VP -580) fortwo -player or three -player interaction.

VIPMade by RCA, New Holland

Avenue, Lancaster,PA 17604.

Phone 717-397-7661.

Western Canada: RCA,6303 30St SE, Calgary,

T2C 1 R4.Phone 403-273-1815.

Dealers are just being setup in the West, but try

these: Byte Shop in Van-couver, Computer Slop in

Calgary, Orthon in Edmon-ton, and Advance IndstlElectronics in Winnipeg.

SAMPLE SYSTEM(Note all prices are US pricesin US dollars)

Cat. No. PriceCOSMAC VIP Computer -

VIP $249Colour Board -

VP -590 $69Second Keyboard -

VP -580 $15Total Cost Of Above System(excluding colour TV) -

In USA $333

- UpgradesThe VP -590 and VP -580 are men-tioned in the Sample System.

The VP -595 is a sound boardwhich gives one of 256 tones forUS$24.

The VP -550 is a music boardwhich gives two channels and con-trol of frequency, time and amp-litude, for US$49.

VP -570 is a 4K RAM board forUS$95.

VP -700 is 4K of ROM 'TinyBASIC', which needs ASCII -en-coded keyboard, for US$39.

A suitable keyboard is prom-ised for under US$50.

VP -560 is a board to locatetwo 2716 EPROMs (2K each)anywhere in 32K of memory, forUS$34.

VP -565 is a US$99 EPROMprogrammer which generates itsown high voltage, designed for2716 2K EPROMs.



11111nlM;MEMORY SIKETTERMINAL WIDTH?DAZZLE -WRITERRUNNING WITHOK OASIC!!.!

Top Left: The Z -2D with single disk drive fitted.Top Right: Inside the Z-2, showing the 5100 card frame.

Bottom Line: The two plug-in boards of the TV Dazzler. Insteadof the terminal listed in our Sample System you could use the Dazzle

Writer (middle picture) plus TV and suitable keyboard. The chess displayshows the Dazzler at its best (well, it would be better on a colour TV!).

Sample System

9

Z -2W:The Cromemco system is based on theS100 bus. The Z-2 gives you a full-lengthshielded motherboard with 21 card slots.It includes a heavy-duty power supply(+8V @ 30A, +/-18V @ 15A) which willpower a full set of cards plus floppy diskdrive. It comes with a CPU card - the$395 Zb0-based 4MHz 'ZPU-W'. TheZ-2 prices shown are for an assembledunit.

4FDC-W:The Disk Controller card is capable ofsimultaneously interfacing three 5in orfour 8in disk drives. It includes an RS -232interface with a software -selectable rangeup to 76,800 baud. A 1K byte PROMholds the bootstrap monitor.

WFD:The 5in disk drive stores 92K on eachdiskette side in a soft -sectored IBM format.

Z -2D -W:The Z -2D is a Z-2 computer with DiskController and Disk Drive fitted.

16KZ-W:This 16K RAM card will operate at 4MHzwith no wait states. Access time is 200 ns.

The card is 'Bank Selectable' - an 8 -posit-ion DIP switch on the board locates thememory in one of eight banks, which areselected under software control via oneof the output ports. This way the comput-er can access up to half a megabyte ofmemory; and in a time-sharing applicationthe bank select feature can be used tohandle up to 8 users with a minimum ofsoftware overhead.

FDB-S:The Cromemco 16K Disk -Extended BASICcomes on a 5in diskette. It features 14 -digitprecision, extended string and sub -stringhandling, PRINT USING for Cobol -likeformatted output, TRACEing of programexecution, dynamic error trapping, randomand sequential disk file access, programchaining and overlays, multiple statementsper line, renumbering of lines, and directmachine -language interactions using INP,OUT, PEEK, POKE, and USR commands.

3100:This CRT terminal has capacitive keyboardand numeric and cursor pads. It commun-icates to the computer via the RS -232interface. Upper and lower-case lettersare displayed eighty -to -the -line on a 24line display. The price includes a 10ftcable with DB-25P connector.

Z2D

Made by Cromemco Inc,280 Bernado Ave, Mountain

View, CA 94040.Phone 415-964-7400.

Available from ComputerMart & Trintronics in Toron-to, Futur Byte in Montreal,

and Robo-Tronics & TheComputer Shop in Calgary.


Chassis, PSU & CPU Board -Z -2-W $1435

Disk Controller Board -4FDC-W $860

5 inch Disk Drive -WFD $655

Two 16K RAM Cards -16KZ-W $86016KZ-W $860

16K Disk Extended BASIC -FDB-S $130

Terminal -(anybody's) $2000

Total For Above System -about $5200

Upgrades

The S100 system used in the Z-2makes it very versatile, very ex-pandable. Standard cards makeup the computer described as oursample system.

The TV Dazzler is a couple ofcards that map memory onto aTV screen in colour. Definition is128x128 lie 2K bytes of memoryfor simple mapping). Eight col-ours are available and 16 grey -scale levels. Output is video.

The D+7A is an I/O card whichcouples two game consoles tothe computer. The consoles eachhave an x -y joystick, an audioamplifier and speaker, and fourpush-button switches.

Cromemco also have a widerange of cards for everything frommemory, through I/O, to CPU.

48 ETI CANADA -JUNE 1979

DEALERS

The list below is made up from the lists given to us by themaufacturers of the computers in this catalogue. Someof the names we were given were not easily traceableand are not in this list.

Because of the large number we did not list PET dealerson page 43. Here they are marked with a (4, ).

BRITISH COLUMBIAConti Electronics Ltd..5656 Fraser StreetVancouver, B.C.604-324-050.

V.F.A. Systems Ltd.#1-2285 200th Street,Langley, B.C.604-530-8572.

Sound -Comm Distributors,1708 Bowen RoadNanaimo, B.C.604-754-1911.

Basic Computer Group1438 East 8th,Vancouver, B.C.604-736-7474.

Heathkit Electronics Centre,3058 Kingsway,Vancouver, B.C.V5R 5.17604-437-7626.

Kerridale Compute -Micro,2071 W 41st. Ave,Vancouver, B.C.V6M 1Y7.604-263-0934.

The Byte Shop,2151 Burrard SI,Vancouver, B.C.V6J 3H7.604-736-0511.

ALBERTAThe Computer Shop*3515 -18th Street W.Calgary, Alta.403-455-5298,403-243-0301.

TJB Microsystems Ltd..Box 4844,Edmonton, Alta.403-455-5298.

Orthon Holdings Ltd,12411 Stony Plain Rd,Edmonton, Alta.T5N 3N3

Compu-Shop4014 MacLeod Trail Sth,Calgary, Alta.403-243-3846

The Computer Shop of Alberta,723 14 St. NW,Calgary, Alta.403-283-0751

Heathkit Electronic Centre,12863 -97th St.Edmnnton, Alta.T5E 4C2403-475-9331.

Robo-Tronics,509 -16th Ave. N.W.Calgary, Alta.403-282-9496.

SASKATCHEWANMicro Shack Ltd..Box 3733,Regina, Saskatchewan306-543-4079.

Digital Service,.1310 East Centre,Saskatoon, Sask.306-374-8908.

Sask. Sound City Ltd.1007 -20th Street W.Saskatoon, Sask.306-653-2641.

Custom Computing Systems,3-204 2nd Ave. North,Saskatoon, Sask.306-242-7808.

MANITOBAAlberts Controls Ltd*504 Logan Avenue,Winnipeg, Man.204-947-6929.

Percomptron Inc..c/o The Byte Shop,665 Century Street,Winnipeg, Man.204-453-6544.

Computerland of Winnipeg,.715 Portage Ave.Winnipeg, Man.204-772-9519.

Heathkit Electronic Centre,1315 Portage Ave.Winnipeg, Man.R3G OV3,204-783-3334.

Advance Industrial Electronics,1400 Portage Ave. W,Winnipeg, Man.

ONTARIOTORONTOComputer Workshops Ltd 1240 Bay Street Mall,Toronto, Ont.416-923-1917.

The Home Computer Centre,.6101 Yonge Street,Willowdale, Ont.416-222-1165.

Computermart,.1543 Bayview Avenue,Toronto, Ont.416-484-9708.

Hamtraders,045 Brisbane Road, Unit 18,Downaview, Ont.416-661-8800.

Richvale Telecommunications,.Unit 18, 10610 Bayview Avenue,Richmond Hill, Ont.416-884-4165.

T. Eaton Stores 0

The Bay Stores.

The Robert Simpson Co.0

The Computer Place,186 Queen St. W.,Toronto, Ont.M5V 1Z1.416-598-0262.

r::::::,......m....,.........,::::::::::::,::::::::::::::.:,::::::,......gOMPUMART a:1

1

The Personal Computer Store:1.;

is

NOOr KITS from $2359.00reik Assembled from $2759.00

$2.

The North Star Computers HORIZON is a high-performance, Z80Abased microcomputer system which is especially suited for business,educational, and software development applications. It features fast -access DISK storage as an integral part of the package, 4 MHzmicroprocessor operation and built-in I/O capability. The HORIZONuses the S-100 bus structure and each disk now stores 180K bytes.

Available for Dompumart Software: Pack -Expand DiskettePerfect for Structured Programming $25.00Specify single or double density.

INTERTU3EThe Smart Terminal at a Smart Price $1350.00See our May advertisement in ETI

appla°computar

Thousands of people have already discovered the Apple9computer -businessmen, students, hobbyists. They are using their Apples forfinancial management, complex problem solving -and just plain fun.Apples begin at $1695.00 for the 16K model. Write or call for moreinformation.

TERMS: Visa/Master Charge (Please include expiry date),check or money order. Add 2% for shipping and handling.Ontario residents add 7% Provincial Sales Tax.

CO MPU MART, P. O. Box 6132, Station J, Ottawa,Ontario, K2A 1T2; Showroom: 411 RooseveltAve.; or phone (613) 725-3192.

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.,.'7,....... ,, ..... Quality. - ...

..,:. Computer. _ .. Products

Now available

COMPUMARTin Canada from

The Personal Computer StoreMEMORIES ior the S-100 Bus

Econoram I I TM (8K) Unkit $215 Assembled $249Econoram IV TM (16K) Unkit $439 Assembled $479Econoram VI Erm(24K I Unkit $679 Assembled $729

NEW, Econoram XTm (32K) Unkit $939 Assembled $989FEATURES: Fully static memory Dip switch address selection(no wire jumpers). 450 ns access time. High quality, doublesided. plated through, solder masked and legended circuitboard. Sockets for all ICs..UNKITS: Sockets, bypass caps pre -soldered in place for easyassembly.4 MHz operation guaranteed for Econoram IV, VII and X.

MEMORIES for other BusesHEATH H-8: 12K Econoram V ITm Unkit $325 Assembled S395NEW! DIGITAL GROUP: 32K Econoram IXTM Unkit $995ram SBC (Intel/National 80/10 and 80/20 computers):

32K EConoram X ITm CSC* $1595TRS-80 Conversion Kit: Upgrade your 41(*TRS-80 to 16K iuronly $215. Complete with DIP shunts. 1 Year warranty.

OTHER S-100 PRODUCTS from GodboutACTIVE TERMINATOR KIT: Promotes reliable accurate dat,transfer by minimizing ringing, crosstalk, other noise

. ,,,,, only $49.9511 SLOT S-100 MOTHERBOARD UNKIT: All 11 edge conn-ectors soldered in place Indi 1( los .1, I've termination... $149.0018 SLOT S-100 MOTHERBOARD UNKIT: 18 slot version ofabove $195.00FROM FORETHOUGHT PRODUCTS:BETSI: PETTMt0 S-100 interfaceKit (with 2 S-100 edge connectors) $199.00Assembled (4 S-100 edge connectors) $269.00

KIMSI : KIM-1Tm to S-100 interfaceKit (with 2 S-100 edge connectors) $215.00Assembled (2 S-100 edge connectors) $269.00

BACK ISSUES of KILOBAUDDec11978), February, March, April, May(1979) - $3.25 ppdDealer Enquiries Invited.

*CSC (Certified System Component program). 200 hourburn -in, guaranteed 4 MHz operation over the full comm-ercial temperature range, serial numbered, Immediate replace-ment in the event of failure within 1 year of invoice date.Also available for Econoram IV ($639), V11($91 9), X ($1 195 )

TERMS: Visa/Master Charge (Please includeexpiry date), check or money order. Add2% for shipping and handling. Ontario resid-ents add 7% Provincial Sales Tax.

COMPUMART, P.O. Box 6132, Station J,Ottawa, Ontario, K2A 1T2. Showroom: 411Roosevelt Ave.; or phone (613) 725-3192. i

DEALERS, cont'Trintronics.186 Queen St. W..Toronto, Ont.416-598-0260.

Compucentre,20 Bloor St. E.,Toronto, Ont.416-961-5978.

Hamilton-Avnet,3688 Nashua Drive,Units G & H,Mississauga, Ont.416-677-7432.

Computer Methods Ltd.Suite 205, 2249 Yonge Street,Tornto, Ont.416-482-5100-2.

Micro Ware,.2334 Danforth Avenue,Toronto, Ont.416-424-1413.

Comspec Communications,.944 Wilson Avenue,Downsview, Ont.M3K 1 E7.416-633-2871.

Batteries Included,.Village By the Grange,71 McCaul Street (F6),Toronto, Ont.416-596-1405.

Efstonline Inc..3500 Bathurst Street,Toronto, Ont.416-787-4583.

House of Computers Inc.368 Eglinton Ave. W.,Toronto, Ont.416-482-4336.

Nakcomm Sales & Service,.80 Hale Road, Unit 7,Brampton, Ont.416-459-7616.

Heathkit Electronic Centre,1478 Dundas St. East,Mississauga, Ont.L4X 2R7.416-277-3191.

Datamex,14 Leswyn,Toronto, Ont.M6A 1 K2416-787-1208.

OTTAWAFocus Scientific Ltd.409 Rideau Street,Ottawa, Ont.613-236-7767.

Compumart,0411 Roosevelt Avenue,Ottawa, Ont.613-725-3192.

Computer Innovations,171 Slater Street,Ottawa, Ont.613-233-8413.

Wackid Radio,312 Parkdale Ave.,Ottawa, Ont.K1Y 1G3.

Hamilton Avnet,1735 Courtwood Crescent,Ottawa,Ont.K2C3J2613-226-1700

Heathkit Electronic Centre,866 Merivale Road,Ottawa, Ont.K1Z 5Z6.613-728-3731.

REST OF ONTARIOBMB Canada..395 McNabb Crescent,Milton, Ont.878-4909.

Edward S. Grabas,.Box 18, RR #1,Chalk River, Ont.613-589-2083.

Colormaster Inc 3095 Forest Glade Drive,Windsor, Ont.519-945-2348.

The Computer Circuit Ltd.737 Richmond,London, Ont.519-672-9370.

North Star Computer Ltd..1729 Virginia Drive,Sudbury, Ont.705-522-8420.

Orion Electronics,49 Lancaster St. W.,Kitchener, Ont.

QUEBECFuturbyte1191 Phillips Square,Montreal, Que.514-861-3120.

Central Distributors Ltd,350 Des Erables,Lachine, Que.514-364-4222.

Hamilton Avnet,2670 Paulus StreetSt. Laurent, Que.H4S 1G2514-331-6443

irisco Du Quebec Inc..537 Boul. Charest Est,Quebec, Que.418-647-4422.

Harts Department Stores..9200 Claveau Street,Ville D'Anjou, Que.514-354-3810.

T. Eaton Co..677 Ste. Catherine St. W.,Montreal, Que.

Cesco Electronics Ltd.4050 Jean Talon Street W.,Montreal, Que.514-735-5511.

Heathkit Electronic Centre,795 Legendre St. E.,Montreal, Que.H2M 1H1,514-384-9160.

Compucentre,9200 Claveau St.,Montreal, Que.H1J 1Z4.(Stores In Place Ville Marieand Place Bonaventure)

NEW BRUNSWICKinteractive Computer Systems, Ltd.105 Fir Court,Fredericton, N.B.506-455-8994.

NOVA SCOTIAMiniComp Systems,.5666 Stanley Street,Halifax, N.S.902-455-5123.

Kobetek Systems Ltd.RR X1,Wolf villa, N.S.902-542-2500.

Lantz Electronics Ltd 15 Clifford Street,North Sydney, N.S.902-794-3102.


ETI Project Light Show Colour Sequencer

Light ShowColour SequencerThis unit interlaces with the ETI 592 Light Show Controller to givea rainbow sequence of colours.

BY MIXING THE THREE primarycolours in the right proportions anycolour of the rainbow, including white,can be made. A good example of this isa colour TV set, which uses only red,green and blue phosphors. When creat-ing special effects with lights it is oftendesirable to have a colour which changeswith time be it for a spot on a disco wallor lighting up a fountain.

This unit allows three light dimmers(the ETI 592 is ideal) to be controlledin a preset sequence giving eight differentcolour mixes. The rate of change fromone sequence to the next is also variable.

DESIGN FEATURESWhen we first examined the differentways of designing this project we hadthe choice of a simple system using amultitude of potentiometers or onewhich uses digital techniques with aRAM and D -A converters. Due to thecomplexity of the digital approach wechose the simple analogue system.

CONSTRUCTIONThis is simply a matter of following thecomponent overlay in fig. 2. Note thatthe trimpots are staggered to allowadjustment or to allow the larger typeto be used without interfering with theadjacent pot.

Check the orientation of the ICsbefore soldering and solder the powersupply rails first (especially for theCMOS ICs).

The power for the unit comes froman external supply. If it is to be usedwith the ETI 592 dimmer power can betaken from that unit. Otherwise a supplygiving a positive voltage of between 10Vand 15V (regulated) and a negativevoltage of -2V to -15V is needed.Supply current on the positive supply isabout 10mA while it is only about 3mAon the negative side.

SPECIFICATIONS

Number of channels

Speed

Output VoltagePower Supply

3

3 - 30 seconds per step

0 - +7VT 12V @ 10mA

SETTING UP

Connect the unit up and switch on. Onswitching SW1 on the unit shouldsequence through its cycle. Stop theunit and check to see which potentio-meter in each bank controls the light.

Adjust the level of the three dimmers togive the desired colour and intensity.

Close the switch until the next stageis selected, open the switch, and adjustthe next colour. Proceed until all eightstages of the sequence have beenprogrammed


ETI Project

1

9-,7

9

0-.10

OV

+12V

H16 15

3

IC14520

5

+12V

OV

R3 3V2 RV3 RV4 RV5 RV6 RV72k2 25k 25k 25k 25k 25k 25k

RV8 RV925k 25k

SVV1

R1100k

RV 11M

R210k

1,C1

+12V0

OV

0

-12V

IC2555

2

1C2

1100nC3100n

0 0 12V

+12V

0 OV

111314

10

9

15 12

IC34051

6 7 8 16

2 4

+12V

OV

R42k2

RV1025k

RV1125k

RV1225k

RV 325k

OV +12V

R6100k

3

C4 2

RV 4 RV1525k 2Ek

0

RV 6 RV1725k 25k

R52k2

+12V

OV -016

113

10

14 15 12

IC44051

6 7 8 16

2 4

OV 12V

RV18 RV19 RV20 RV21 RV22 RV2325k 25k 25k 25k 25k 25K

RV24 RV2525k 25k

13 14 15 12

IC54051

6 7 8

Fig. 1. The circuit diagram of the sequencer.

The unit consists of three identicalchannels controlled by a master selector.There are eight potentiometers associatedwith each channel which are used simplyas voltage dividers. The 4051 IC associatedwith each set of potentiometers is a one ofeight analogue multiplexer which meansthat one of the potentiometer outputs willbe connected through to the output of theIC (pin 3) depending on the binary code

10

9

2

I

iOV +12.

HOW IT WORKS

R8100k

+121

IC6a324

4

11

-12V

10

C633p

OV

IC6c324

R91k

R111k

0/P 1

0/P 3

presented to the control inputs (pins 9,10and 11).

The output from the 4051 is bufferedby an op -amp with an RC network to givea slow change from one level to the next.The value of the capacitor can be reducedif the response is too slow. As the op -ampcannot swing to its supply rail a droppingresistor is used in series with the potentio-meters limiting the maximum voltage to

the op -amps to 7 volts.The channel selection is done by IC1

which is a dual 4 bit binary counter. Weare only using it as a single 3 bit counterwith the unused inputs terminated to thesupply rails. This IC is clocked by the 555timer IC2 with the rate being determinedby RV1. Again if the rate is wrong Cl canbe changed in value.


- Light Show Colour Sequencer

RV 11

RV 1

RV 13

RVt

RVt

t6 t t6 F"Co,ICS

RV RVit RV7 RV6 RV5 RV4 RV3 RV2

S

V1 SW1

+12V

OV

.`. -12V

+0/P 1----0/P 3-0/P 2

R5

AVIRVtt IR#1471Fig. 2. The component overlay.

ETI Rescue Service is fullyoperational. Many back issuesare available and importantinformation can be suppliedfrom those which are not. So ifyou lose a copy send us detailsand $2 (not cash) for each issueyou require, to ETI BACK -NUMBERS, Unit 6, 25 OverleaBlvd., Toronto, Ontario M4H1B1.

Check page 82 inside the backcover to see which issues areavailable.

111M=INIME nomin=Mp

RESISTORS all 4W, 5%RI 100kR2 10kR3-R5 2k2R6-R8 100kR9-R11 . 1k

POTENTIOMETERSRV 1 1M trimRV2-RV25 . 25k trim

CAPACITORSCl. . . . . . . 33µ 16V electroC2,3 100n polyesterC4-C6 33µ 16V electro

SEMICONDUCTORS1C1 4520 counterIC2 555 timerIC3-1C5 . . . 4051 multiplexerICS 324 quad op amp

MISCELLANEOUSPC board ETI 593single pole switch

PCBs for this project are available from: B &R Electronics, P. 0. Box 6326F, HamiltonOnt., L9C 6L9, and Spectrum Electronics,38, Audubon St. S., Hamilton, Ont., L8J 1J7.Kits of parts and boards are available fromNorthern Bear Electronics, P. 0. Box 7260,Saskatoon Sask., S7K 4J2.


CCCIDUATI-1-11JILLEADING

These Babani Books are now available:

No. Title Price

215 Shortwave Circuits and Gear for 2.60Experimenters and Radio Hams

221 28 Tested Transistor Projects 2.85223 50 Projects Using IC CA3130 2.85BP1 First Book of Transistor Equivalents 2.00

and Substitutes52 Projects Using IC741 2.40Electronic Calculator Users Handbook 2.9050(FET) Field Effect Transistor Projects 3.55

B P24BP33B P39BP44BP46BP47BP48BP49BP50BP51

IC555 ProjectsRadio Circuits Using IC'sMobile Discotheque HandbookElectronic Projects for BeginnersPopular Electronic ProjectsIC LM3900 ProjectsElectronic Music and Creative TapeRecording

4.004.504.504.304.804.504.20

Please add 30¢ per book for postage and handling,and use the card in this issue to order.

11111111111111111111111111111111111111111111111111111111111111111111111111111111U1

= Specially Imported for Canadian= Hobbyists:

Another Circuits Book:

`CA3130'2 50 Projects Using IC CA3130

F.-.

.1 Published in the UKin February 1977

About the IC Audio Projects RF Projects Test Equipment Household Projects Miscellaneous Projects

$2.85 (Size 71/8" x 41/4")

E.-- Please include 30c forpostage and packing.

Send order with cheque orChargex/Mastercharge number

I.§ (with expiry date and signature)

By R. A. Penfold96 pages

to:ETI Books, Unit Six, 25 OverleaBlvd., Toronto, M4H 1B1.

1111111111111111111111111111111111111111111111111111111111111111111111U1111111111

AU, /Mr AI /Mr /Mr /Mr AP' d11, AI AN, Amr

Specially Imported from England!

Electronic Projectsfor BeginnersBy F.G. RayerPublished August 1978

$4.30 30¢ postage & handling.

CEDNTENTS

INTPODUCTION

SECTION I NO SOLDERING.. PROJECTS

T.60NN 006tIE .

SCR Comrolled LPN ..-.....Trulliva zercom

1961.1.1 , SupBout Speaker

hD11.1 WWI lullutar _

°NNW MowLED Wawa.119.1

Tumour Tr.Engem LSO..

SECTION, RADIO AND AUDIO ERE(1.Spostrt

1414.1 Oluk RAJ6. EwerON Tram. 61N Rueuet

St6lun6 RnolutENT ININN166,14t PreamplifInTom Cantral fa You D. EtcTAN Clamel Itur

SE

60

74

SWOON, NISEI LIANFOUS DEVICESSNWIt911lrTnr.tu A...

19 1 Nan IC Ampli.am A An/1..Two S., Aniplirre

Cw. . 4/1ECTION POWER SUPPLIES

Two Dow Nm . Eau Revalued PSI!WT Oullegor , 41 1119 Voluto Rerulatul PSC

Ttimatot 416*.N6 PSUUTE NO VOW taw Ewen Regulma St.lySoul 111whow1.6.1111, St

PSU tn. Prunewren. bznIT NtuwIw

46w. IvultUt Poeuces

EQUIV ALENT SENICONDUCTOilt

105

017

(Not actual size)

Please use the card to order.

54

.P tor 66 Aor mr .ar III AN


ETI Project VHF Log Periodic Antenna Pt II

VHF Log PeriodicAntenna Pt IIBy Roger Harrison, who still swears (SWR's?) the prototype hasn't fallendown yet!.

BALUN CONSTRUCTIONTHE BALUN TRANSFORMER consistsof a trifilar winding on a ferrite baluncore, Neosid type 1050/2/F14. Alter-natively, a similar core could be strippedfrom a standard 4 - 1 TV balun andrewound. These are found in TV andFM 75 to 300 ohms adaptors. Con-struction is relatively non -critical, anddetails are illustrated in Fig. 7.small -gauge hookup wire, preferably inthree different colours to identify thedifferent strands and assist construction.Alternatively, ordinary enamelledcopper wire, about 22 gauge to 28 gaugeAWG, would be satisfactory, althoughthe three separate wires would have tobe identified in some way, for example,by knotting wire 'b' once at each end,and wire 'c' twice at each end.

The three wires need to be about 150mm long and should be lightly twistedtogether before commencing thewindiry. Wind 61/2 turns through thetwo holes, around the outside of thebalun core as illustrated in Figure 7.

a b c

WINDING BALUN

Ferrite(Neosid 1050/2/F14)or similar

The wound core is then glued to asmall square of matrix board, about 25mm long per side, using a small amountof five-minute epoxy or one of the'super' glues. The windings areterminated to two pins on either side ofthe board, as illustrated in Figure 7.Two lengths of hookup wire should besoldered to the 'balanced' terminals,sufficient to reach from the mountingpoint of the balun to the feedpoint ofdipole 10. A short length of coax,terminated in a line socket, is thenattached to the 'unbalanced' terminalsas indicated.

The balun assembly can beconveniently 'potted', using five-minuteepoxy, to weatherproof it.

jalanced

C

balancedE0LL

Mount the balun on the antennaboom, near or underneath, dipole 10,and connect the two 'balanced'connection leads to the feedpoint ofdipole 10. Tape the assembly to theboom using weatherproof tape or plasticties. Even string could be used, or theassembly glued in position using somemore five-minute epoxy.

An alternative balun system wouldbe to use standard 4 - 1 TV baluns.These perform a 300 ohm to 75 ohmtransformation. With the type ofconstruction employed, they can beused for a balanced -to -balanced or a

balanced -to -unbalanced transformation.

CIRCUIT

CONSTRUCTION

unbalanced

Fig. 7. Construction of 1:1 balun transformer.


ETI Project

0I -

Coax from antenna

27 ohm

27 ohm 27 ohm

CIRCUIT

Aluminium panel (back view)

27 ohm1/2 W or Y. W

resistor

75 OHM SYSTEM SPLITTER

SPLITTERSTo run two different receivers from acommon antenna a device called asplitter is necessary. The two receiverscannot simply be connected in parallelas they will interact with each other,apart from causing an impedancemismatch with the antenna feedline.

Two different kinds of splitters calbe constructed - the resistive type andthe transformer type. Alternatively, asuitable splitter may be purchased. Asthey are wideband devices they aresuited for operation over the entirerange from 40 MHz to 250 MHz.

To FM receiver

coax socket

CONSTRUCTION

If using these baluns, connect the 75ohm side to the feedpoint of dipole 10and run ordinary 300 ohm ribbon toyour receiver installations from the 300ohm balun connections. Be sure totake all the required precautionsnecessary with this sort of feedlineinstallation as for TV feeder, to preventsignal 'suckout' by nearby metalstructures and by line imbalance.

300 ohm twin linefrom antenna

Twin lineto TV receiver


CONSTRUCTION 220 ohm'/2 W or Y. W

resistor

Screwterminalpanels

CIRCUIT

300 OHM SYSTEM SPLITTER

Fig. 8. al Circuit of 75 ohm resistive splitter.bl Layout of 75 ohm resistive splitter.cl Circuit of 300 ohm resistive splitter.dl Layout of 300 ohm resistive splitter.

RESISTIVE SPLITTERSTwo resistive -type splitters areillustrated in Fig. 8. That on the leftis for unbalanced, 75 ohm coaxialcable feedline systems; the one on theright is for 300 ohm systems. Both ofthese splitters are compromisesolutions and are only recommendedfor TV & FM receiver installations instrong signal areas. If you are after

Twin lineto FM receiver

DX, then the loss these splitters intro-duce will reduce receiver sensitivity.

Either type may be constructed ona small square or rectangularaluminium plate. Size is unimportantproviding the feedline connectors aremounted reasonably close togetherso that the lead -length of the resistorsand interconnections is kept short.Solder tall connections.


Note that any terminal may be usedas an input and the other twoterminals may be used as the outputs.

When the splitter construction iscompleted, it can be mounted in aconvenient place such as a cutout in awall, shelf, or equipment cabinet.

TRANSFORMER SPLITTERThe best splitter is a transformer -typeas it introduces a minimal loss, and canbe constructed in a similar way to thebalun previously described.

Commence by winding three wireson a balun core as shown in Fig. 7 andwind on 6% turns, trifilar as describedfor the balun. The connections andconstruction are as illustrated in Fig. 9.

Once the transformer is completed,secure the windings, if necessary, witha small application of super glue. Thenglue the transformer to a small scrapof plain phenolic board or matrixboard. This assembly is glued to asmall aluminium panel on which aremounted three coax sockets as illust-rated in Fig. 9. Carefully separateand identify the three leads at eachend of the transformer windings andconnect them as shown. Carefullysolder all joints.

When the construction of the)litter is complete it can be mounted

as described for the resistive splitters.

FEEDLINE SYSTEMSThere are two alternatives for yourfeedline system: a 75 ohm coaxialcable system, or a 300 ohm twin -linesystem.

The coaxial cable system is

recommended for a number of reasons:the coax may be run anywhereconvenient as it is unaffected by wallmaterial, metal objects and powercords. Many VHF receivers, TV setsand FM tuners these days have a coaxconnector antenna fitting to suit, andno interference can be picked up onthe coax feedline as it is effectivelyshielded.

A 300 ohm twin -line feeder has theadvantage of being inexpensive, but itmust be correctly installed with stand-off supports and twists in the line toaid in maintaining 'balance'. It cannotbe run as conveniently as coax, andnoise and multi -path signals may bepicked up on the feeder.

The required use of baluns andsplitters in the system is illustrated inFig. 10 for both systems. The 75 ohmcoaxial cable system is illustrated onthe left and the 300 ohm twin -linesystem on the right.

VHF Log Periodic Antenna Pt II

The coax required depends on theexact details of your installation. If ashort run of coax is possible then a 6.5mm diameter cable such as RG59(variously designated as RG59/U orRG59/CU etc.), which is a 75 ohmcharacteristic cable, is suitable. If thiscannot be obtained, then 50 ohmcable such as RG58 may be substi-tuted, although a slight mismatch willresult. The effect will be unnoticeableon a VHF or FM receiver but slight'ringing' may be apparent on highcontrast areas on a TV picture. Thismay not be visible at normal viewingdistances.

For maximum sensitivity onreception or if you have to run thefeedline more than 15-20 metres, thena low loss 75 ohm cable isrecommended with black, weatherproofouter jacket.

Fromantenna

Ferritebaluncore

Solderlug

Input (75 ohm)

CONSTRUCTION

CIRCUIT

27 ohm'4 W or 1/2 Wresistor

If you wish to use a 300 ohmfeeder system, any of the commonlyavailable TV ribbon feeders shouldsuffice, depending on your require-ments. Solid dielectric type isadequate in strong signal areas and isthe least expensive. If you want themaximum in sensitivity a low -losstype should be installed. There arevarious versions of low -loss 300 ohmfeeder. Some types are similar to thesolid dielectric type and simply havecutouts in the dielectric. 'Open wire'types have small spacers supportingthe two wires at intervals. Anothertype has a continuous dielectric offoam material encased in a thin plastic'shell'.

27 ohm1/2 W or '4 Wresistor

Receiver 1 (75 ohm)

Outputs

Receiver 2 (75 ohms)


Fig..9. al' Circuit of transformer -type splitter.b) Construction of transformer -type splitter.

Phenolic or matrix boardinsulating sub panel


ETI Project VHF LC0 Periodic Antenna Pt II

ANTENNA PERFORMANCE

The beamwidth of the antenna isabout 50° (between the -3dB points).There were no discernable sidelobes inthe forward direction which reducesproblems with multi -path signals onFM and TV reception which are thecause of distortion on FM stereo andghosting on TV signals.

The gain of the antenna is aroundeight to nine dB and the front to backratio (rejection of signals behind the

1:1 balun (Fig. 7)

75 ohmcoax (RG59)

15 ohm sp itter(Fig 8 or Fig 9)

antenna) around 30 dB.The broad beamwidth allows

reception over a wide range of anglesin the forward direction, very handywhen the DX starts pouring in from allover the place as it saves a great dealof rotatina the antenna. If you areusing it for TV/FM reception thebeamwidth should prove adequate formany city locations. However, you maythink that you will have problems witha fixed antenna.

0 0000O0 FM receiver

0

4:1TV balun

Installed at a height of roughly sixmetres above ground level, the antennagave a good account of itself.Admittedly, as far as the local TV andFM transmitters are concerned I live ina strong signal area, although we havein the past suffered from ghosting onTV signals from the south. The goodfront -to -back ratio improved thisproblem considerably.

300 ohm

75 ohm coax(RG59)

5 ohm

TV receiver Fig. 10. Feedline and splitter systems installation. TV receiver

300 ohmtwin -line

TV ribbon

75 ohm splitter(Fig 8 or Fig 9)

OR

FM receiver

300 ohmsplitter(Fig 8)

to 300 ohminputs onreceivers

ALPHA . TUNER . SERVICEThe Name of Quality in Tuner Servicing

Repairs to all types of tuners Domesticor Import. Colour or Black & White.Tube, Transistor or Varactor.

Tuner repairs are our specialty. We useonly original or Superior components togive top performance and reliability.

Fast Coast -to -Coast Service. Majorparts and shipping charges at cost,(dealer net). Bring your tuners to ourMontreal centre or forward by mail.

VHF or UHF $13.95 Varactors $13.95 FM Tuners $15.95 UV Combo $21.95 Parts and workmanship

carry full 12 monthswarranty.

ats electronics3226 6th Street, P.O. Box 172,

Chomedey, Lava , Quebec H7V 3P5 (514) 681-0501

58 ETI CANADA JUNE 1979

ETI Project

Bip BeaconA.J. Lowe designed this project to help a friend from his local Blind Assoc atior.All the device does is emit a continuous series of 'bips' to enable a blind personto get his bearings. So if you know anyone who might like one, have a go atmaking this simple project.

WHEN BLIND PEOPLE put somethingdown, working around the house orgarden, they sometimes have difficultyin locating it again. The Bip Beaconprovides a sound signal on to whichthey can 'home'.

When two blind people arrange tomeet at a certain place, each hasdifficulty in knowing when the otherhas arrived. The Bip Beacon providesan innocuous signal that says 'I'mhere'.

You can build a beacon for about$3. If you don't know any blind peoplecontact your local Blind Association,they'll be glad to hear from you. Manyof these beacons have been built andeagerly accepted by blind folk.

WHAT IT DOESThe beacon simply emits a series of'bips' (a 'bip' is a short 'beep') at foursecond intervals. That's all, but it'senough.

HOW IT WORKSThe circuit, shown in Fig. 1, is basedon one IC, a quad two -input NOR gate.Two of the gates form a slow.runningmultivibrator the output of whichenables the other two gates to form anoscillator whose output is amplified bytransistor 01. Component values arechosen so that a short duration audionote is produced every four secondsOr so.These beacons are most convenientlybuilt in transistor radio cases. Mostreaders will be able to find one or twoof them in which the radio is dead andnot worth fixing. As long as the caseand speaker are intact that's all thatmatters.

A suitable printed circuit boarddesign is shown in Fig. 3. The actual

circuit is in the middle of a boardmeasuring 65 x 50 mm. This size is largeenough to reach the support posts in thetypical pocket radio.

The board should be cut and shapedto suit the exact shape of the case. Agood way of doing this is first to makea cardboard template and get that right,and then use it to mark the pc board forcutting.

Care must be taken in locating theholes in the board for the mountingscrews. Holes are not shown in Fig. 3as they must be drilled to suit eachindividual case. A good way of findinghole positions is to make a transparenttemplate from stiff plastic film, usingthe card template as a guide. The

Bip Beacon

.104 10 0it 06* ***** -6 0 - -'411 e

support posts can be seen through thisclear template and it is easy to markthe hole positions and transfer them tothe pc board.

All this cutting, shaping and drillingshould be done before mounting anycomponents.

Next mount all the componentsexcept R2, whose value must be deter-mined on test to allow for variations inthe value of C1. Take care with thecorrect orientation and handling of IC1which is a CMOS IC.

The board, with all comporic itsexcept R2 mounted, is then hooked upto the battery and speaker and a valueof R2 selected so that the bips occur


ETI Project

The photographs above show the constructionof the Bip Beacon on a pcb which fits inside acheap transistor radio case.

every four seconds. As R2 is a highvalue resistor 5.6 megohms or more, itmust not be held between hands duringthis test or spurious results will beobtained. Use test leads with clips.

Finally insert R2 and assemble theboard, switch and battery in the case.See the photos.

As these beacons are needed bypeople who can't repair them them-selves, they should be made verythoroughly - with first class solderedjoints.

CLUBSElectronic clubs who undertake pro-duction of beacons for local blindassociations might approach local chainstores to see whether they can provideany new but 'dud' radios which theymight otherwise throw away.

Well there it is - a not very difficultproject, but a worthwhile one to helpthe sightless to 'see'.

CHIPNot all types of 4001 will work asoscillators, you must specifically requesttype 4001A, not 4001B. Motorola doesnot have an A series, but their 4001(not B) will work.

The pcb artwork.

R1 R2 C1

0'D1 D2

114as,:".°---c708

8 8 LZ:ana g

0-0.0.11

I C 1

TO SWITCHAND BATT+ V E

14 R4 ei

d/01 TO SPEAKER

BAIT- VEC2 R3

4

PCBs for this project areavailable from: B & R Ele-ctronics, P. 0. Box 6326F,Hamilton Ont., L9C 6L9,and Spectrum Electronics,38, Audubon St. S.,Hamilton, Ont., L8J 1J7.

The component overlay.


Circuit diagram of the Bip Beacon

R1220 k

D1

IC1/1

2

D2

IC1/24

1.C1

470nC22n 2

l2IC1/4

R410k

Bip Beacon

A----o +9 V

012N3905OR SIMILAR

R547

SPEAKER8 OHMSMIN

5.6 MEG OR MORE SELECT ON TEST

- PARTS LISTRESISTORS all % wattR1 220 kR2 5M6 or more - select on testR3 390 kR4 10 kR5 47 ohmsCAPACITORSC1 470 n non polarisedC2 2n2 ceramic

SEMICONDUCTORSD1 and D2 diodes 1N914 or similarGn transistor PNP type 2N3905 or similarIC1 4001 ACMOS

Transistor radio case with speaker and 9volt battery.Miniature toggle switch.

- HOW IT WORKS

+9 V -

o v

VOLTAGE AT PIN 4 OF IC1

ovr

SWITCHON

The IC contains four (hence its nameQUAD) NOR gates which are separatefrom one another except for the powersupply connections. Consider any of theNOR gates, such as gate 1, which has itsinput terminals connected to pins 1 and 2of the IC and its output terminal con-nected to pin 3. The NOR description is ashort way of saying NOT OR, and itmeans that - only when the input voltageon pin 1 or pin 2 or both pin 1 and pin 2is high, (i.e. above about 3Y2 volts) thenthe output voltage at pin 3 is low (i.e., atthe level of the negative rail). If neitherpin I nor pin 2 is high i.e. both are low,then the output voltage on pin 3 is high.

That's all there is to a NOR gate.Now, applying this knowledge to theinterconnection of the four gates, thedescription goes as follows:

Consider gates 1 and 2. Immediatelyafter 'switch on' there is no reason whythere should be any voltage at pins 1 2 5and 6. So if 1 and 2 are low, then pin 3must go high. As this pin 3 is connected topins 5 and 6 they must go high, and so pin4 goes low. Now capacitor Cl charges

fairly rapidly from pins 3,5 and 6 throughdiode DI and resistor RI. As CI charges,the voltage at its top end, and hence onpins 1 and 2, increases. When that voltageis high enough gate 1 inverts (because withpins 1 and 2 connected it is an inverter)and its output pin 3 goes low. This makespins 5 and 6 go low, and hence pin 4 goeshigh.

Next, Cl discharges through diode D2and resistor R2 - slowly, as R2 is a veryhigh value resistor. Ultimately the voltageof the top of Cl has fallen to a low valueand so it takes pins 1 and 2 down low. Sopin 3 goes high, 5 and 6 go high, and 4goes low, and the process repeats over andover.

From this description it can be seenthat the voltage at pin 4 would follow thegraph shown in Fig. 2.

Now consider gates 3 and 4. A momentafter 'switch on' pin 8 is low because it isconnected to pin 4 which is low. Also pin9 is low because there is no reason why itshould be high. So pin 10 goes high, and,following the earlier description, pins 12and 13 go high and 11 goes low, C2charges through R3 and when it is

charged, which doesn't take long as it is avery small capacitor, then its top end ishigh. So pin 9 is high. This then sends pin10 low (that's the NOR gate action), pins12 and 13 low, and 11 high. The capacitordischarges rapidly through R3 and thecycle repeats at an audio frequency. Itsoutput, pin 11, turns on and off transistorQ1 and so a note is produced by thespeaker.

However, at any time when pin 8 ishigh gate 3 ensures that pin 10 is held low.Hence 12 and 13 go low and pin 11 goeshigh and transistor Q1 is turned off.

Now pin 8 is connected to pin 4,which, as already seen is high for most ofthe time and low for only a small fractionof the time - while Cl is charging. Thusthe audio output occurs for only shortintervals when pin 4 is low.

By suitable choice of RI and R2 thedevice has been made to give a short bipevery four seconds or so.

The pitch of the audio note can beadjusted by selection of R3 and C2.

As the ICused is of the CMOS type itscurrent drain is very low and a longbattery life can be expected.


Promiseheranything...

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I


ETI Data Sheet STAC Timer

STAC TimerThe National MM57160 is an example of how to REALLY control the timing ofEVERYTHING in sight - it's a microprocessor in disguise.

The standard timer and controller chip is apreprogrammed member of National's Control-ler Oriented Processor (COP) family. The deviceis designed for use in repetitive timing applica-tion where 1 to 4 outputs are to operate at 4user -programmed times. Minimal externalhardware is needed for complete systemimplementation due to direct display drivecapability and a key -switch interrogation fea-ture. Strap selection for 50 / 60 Hz input and7 -day / 8 -day mode has been included foradded versatility.

InitializationPower for the device is a single power supplyof 7V9 to 9V5 Proper initialization will occurinternally if the supply rise time is between 11

s and 1 ms. If the supply rise time to finalvalue exceeds 1 ms, an external RC networkwith a time constant in excess of the supplyturn -on time should be placed on the Power OnReset (POR) pin This delays initialization untilthe power supply voltage is within specifica-tions Initialised conditions are (a) time (real-time clock) at 00 00. (b) all set point times to00 00 and all outputs off. (c) all days valid. (d)present day counter to day 1. and. (e) real-timeclock mode

Setting the time is performed in the normalreal-time clock mode by depressing the SETHOURS (10) or SET MINUTES (9) keys Eachdepression will cause an increment of the hoursfrom 0-23 or minutes from 0-59. respectivelyholding the appropriate key depressed willcause the numbers to roll (slew) at a 4 /secondrate Normal operation is to slew the value closeto the desired setting and then 'bump- it to thefinal value

OPTION SELECTIONStrap switches can be ucrd to implement keyfunctions Figure 1 Must ates strapping ofkeyswitch functions 1-5

ProgrammingFor proper operation, the system must have1 or more of its set point times loaded To load(or program) set points, the DATA ENTRY key(5) must be depressed momentarily to take thesystem from the normal real-time clock mode tothe data entry mode. Upon activation, 1 of theset point times will be displayed and its outputstatus will be shown on the decimal points ofthe display. After power -up, this will be 00 00and the decimal points will be off. To examineor go to another set point, the ADVANCE SETPOINT key (6) is depressed in the data entrymode for each new time. The 4 values are heldin a revolving stack (similar to a calculatingstack) and each advance causes it to roll 1

position. Four advances returns to the originalposition

To activate a set point, the hours andminutes will be loaded with the same SETHOURS (10) and SET MINUTES (9) keys usediri setting the real-time clock. In addition theSET STATUS (8) key is activated and is used toload the output(s) to be activated at the pro-grammed time. Depresssion of the SET

STATUS key causes the 1st decimal point toturn on (which will correspond to output 1

turning on at run time). If this output is the only'one to be used at this programmed time, onecan go to the next set point by using theADVANCE SET POINT key. If, however, the

Features 24 -hour real-time clock with 4 -digit display 60 Hz (50 Hz option) timing derived from the

power line 4 Control outputs at each set point time 4 set point times may be programmed with

repeat every 24 hours Valid day programming to "skip" certain

days Manual mode to verify programming Transducer input to force to a preset condi-

tion Time of day reset to ease time setting or to

allow use as a sequence timer High speed "demonstration" mode for

verification of capability I Single 9V power supply

[041,10!0.4u1S

a a

e

as,SIG

V SIG

01 SEG

0. secs

SIC

SEG

SIC

104 Sec

S I a(

CI

5/

Si

0

0,

01

D4

DS

10

4 CPG,10,514"

11

/4

124

/0

ZS

11

.0

a,04cS0,104

FIGURE 1 Typical STAC Connection

desired output is to be either output 2, 3 or 4,the set status key should be pressed again toadvance to number 2. 3 or 4 Each advanceturns off the previous decimal point.

If a combination of outputs is designed (suchas numbers 2 and 4), the HOLD STATUS key(2) is used to hold the number 2 decimal pointon before the SET STATUS key advancesthrough 3 to number 4 With the use of theHOLD STATUS key and the SET STATUS key,any combination of the 4 outputs Can beprogrammed at each set point. If an error inprogramming occurs, using the SET STATUSkey from position 4 will clear all data (includingthat set by the HOLD STATUS) and the properinformation may be re-entered by following theproper sequence

If conditions permit, the programming canbe verified on the actual outputs by using theMANUAL key (1) This key, when depressed inthe data entry mode, transfers the decimal pointset -status data to the output latches, thus, themotor, solenoid, valve. or whatever is beingcontrolled will be activated. When all 4 timesand their respective output conditions havebeen programmed, the system is returned tothe real-time clock mode by another depressionof the DATA ENTRY key. If the valid dayinformation is not used, the system is ready tooperate.

Depression of the DAY MODE key (7) en-ables setting and display of the current ancvalid day information The current day is dis-played in the left-ost digit of the display and thevalidity of the day in the right -most digit with a"1" for a valid day, and "0" for an invalid"'of4" day As the clock steps through the week.the programmed conditions occur on all validdays and do not occur on invalid days. The SETDAY key (10), when depressed in the daymode, advances to the next day upon eachdepression The SET STATUS key (8), in theday mode, is used to change the validityinformation. Another depression of the DAYMODE key will return the system to the real-time clock mode

Closure of the HOLD STATUS/DEMO key(2) will provide a means to rapidly cycle throughthe programmed sequence or set up an "instore" display With this key closed in thereal time clock mode, time is advanced at therate of 1 hour per second; thus, a 24 -hour dayrequires 24 seconds to verify and a 7 -day weekrequires less than 3 minutes.

Closing key 6 during the real-time clockmode (either normal or demo operation) willreset the clock time to zero without changingthe set point timing but will reset the valid dayinformation.

External InputsThe MANUAL / REMOTE TRANSDUCER key(1), when depressed in the real-time clockmode, will override any time -related program-ming and immediately force output 1 on and 2through 4 off. This condition will remain untilthe next valid set point occurs.

Using ItA table of key functions and an example pro-gram are given on the next page, the permuta-tions are endless'


ETI Data Sheet STAC Timer

KEYNO.

KEYSWITCHNAME

FUNCTION

REAL-TIME CLOCK MODE DATA ENTRY MODE DAY MODE

1 MANUAL/REMOTETRANSDUCER

Remote transducer input; forcesoutput 1 ON, outputs 2-4 OFFuntil next valid set point afterswitch is off

Manual verification mode, allowsdata to be transferred to outputs1-4

(Novel

2 HOLD STATUS/DEMO

Allows rapid demonstration ofsequence by advancing clockat rate of 1 hr/sec

Holds output N ON while pr ogramming advances to outputN.1. N - 1 -4

(None)

3 8 DAY Specifies 8 -day cycle in lieuof 7 -day

Specifies 8 -day cycle Ifs lieuof 7 -day

Specifies 8 -day cycle inlieu of 7day.

4 50 Hz Specifies 50 Hz line frequencyinput

Specifies 50 Hz line frequencyinput

Specifies 50 Hz lii.e liequency input

5 DATA ENTRY Places unit in the data entrymode

Returns unit to the real-timeclock mode

(None)

6 ADVANCE SETPOINT/RESET TIME

Resets time of day to 00.00without changing set pointsbut resets all days to valid

Advances display to the nextset point so that it may beverified or altered

(None)

7 DAY MODE Places unit in the day mode (None) Returns unit to the real-time clock

8 SET STATUS (None) Controls programming ofoutputs. resets output N to-0- (unless preceded byHOLD key) arid advances tooutput N.1

Alternate action key.changes day from valid)-1") to invalid ("0") andvice -versa

9 SET MINUTES Advances minutes display ofreal-time clock

Advances minutes display ofselected set point

(None)

10 SET HOURS/SET DAY

Advances hours display ofreal-time clock

Advances hours display ofselected set point

Advances display to nextday -must be set to currentday before returning toreal time clock mode -

Programming Example

1. Output 1 should turn on at 2:00 a.m., and turn off at4:00 a.m. each valid day.

2. Output 2 should turn off at 2.05 a.m. and turn backon at 4:00 a.m. each valid day

3. Output 3 should turn on at 2:00 a.m and turn offat 2:05 a.m. each valid day.

4. Output 4 should turn off at 3:01 a.m. and turn onat 4:00 a.m. each valid day.

5. Monday through Friday are valid days - Saturdayand Sunday are invalid.

6. It is now Monday, the time is 1:00 a.m.

Given these conditions, it is now advisable to constructan "output truth table":

TIME/OUTPUT 01 02 03 042 00 AM

2 05 AM

3 01 AM

4.00 AM

ON

ON

ON

OFF

ON

OFF

OFF

ON

ON

OFF

OFF

OFF

ON

ON

OFF

ON

The following key sequence may be used to load thepreceding program into the STAG memory.

KEYDEPRESSED

DISPLAY NOTES

0000 Initial displayData Entry 0000Set Hours 0100Set Hours 0200Set Status 0.200 Set point 1 at 2 00

_ a m . output 1 ON

KeyDepressed Display Notes

Hold Status 0 200 Hold output 1 ONSet Status 0 7.00 Output 2 ONHold Status 0 2 00 Hold output 2 ONSet Status 0200 Output.? ON out

put 3 ONHold Status 0 2 0 0 Hold output 3 ONSet Status 0 2 0 0 Output 4 ONAdvance Set Point 0000Set Hours 0100Set Hours 0200Set Minutes 0201

Set Minutes 0202Set Minutes 0203Set Minutes 0204Set Minutes 0205Set Status 0 205 Set point 2 at 2 05

a m , output 1 ONHold Status 0.205 Hold output 1 ONSet Status 0 2 05 Output 2 ONSet Status 0 20 5 Output 2 OFF, out

put 3 ONSet Status 0 205 Output 3 OFF, out

DUI 4 ONAdvance Set Point 0000Set Hours 0100Set Hours 0200

Set Hours 0300

Set Minutes 0301

Set Status 0.301 Set point 3 at 3.01a.m . output 1 ON

Advance Set Point 0000

Set Hours 0100

Set Hours 0200Set Hours 0300

Set Hours 0400

Dual -In -Line Package

TOP vin

/II

.(1)

/1or

/4v00

/I

7-44C

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St G

MC

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tSIG e

FIGURE 2: Pinouts

KeyDepressed Display Notes

Set Status 0 400 Set point 4 at 4 00a m., output 1 ON

Set Status 04 00 Output 1 OFF, output 2 ON

Hold Status 04 00 Hold output 2 ONSet Status 04 0 0 Output 2 ON. out-

put 3 OFFSet Status 04 00 Output 3 OFF, out-

pi.rt 4 ONData Entry 0000 Present timeDay Mode 1 1 Day 1. validSet Day 2 1 Day 2. validSet Day 3 1 Day 3. validSet Day 4 1 Day 4, validSet Day 5 1 Day 5. validSet Day 6 ' Day 6. validSet Status 6 0 Day 6, invalidSet Day 7 1 Day 7, validSet Status 7 0 Day 7, invalidSet Day 1 1 Return to current

dayDemo (Running) Run thru at least one

24 hour cycle inter-mittently (use Hour& Minute keys to"nudge" display toset points) to verifyoutput settings. Afterpassing set point justprior to present time.release Demo key

Set Hours 0100 Present time

Programming of the STAC is now complete. The programwill continue in 24 -hour, 7 -day cycle until manuallyaltered.


ETI Soffspot

StomperThis month since we're concentrating on computers,Softspot is also in this vein, with an example of whatcan be done with screen graphics, in this case on thepopular PET from Commodore. By Pete Howells.

The program, as listed, is suitable for running in 4K on aPET. It is the result of sitting down at the machine anddoing it, and, as you can see, in no way have the mostefficient or elegant solutions to the problem been used.

1 PRINT "DO YOU WANT INSTRUCTIONS (YOR N)

2 GETA$3 1FA$ =""THENGOTO24 IFA$ ="Y"THENGOTO7005 DIMB$(8),C(8)6 YY =160:MM =102:SS =46:SY =327 DATA"7",-41,"8",-40,"9",-39,"4",-1,"6",1,

"1",39,"2",40,"3",418 FORK =1T08:READB$(K),C(K):NEXT

10 REM15 INPUT "SET SPEED (1 TO 10) ";DF16 IFDF>10ORDF< 1 THENGOT01020 DF =DF/50

100 J =32768105 PRINT""110 I =33267111 POKEJ,YY

This is the initialisation bit i.e. printing instructions ifrequired, setting the graphics characters for the targetetc., setting up a table for "key pressed"/"direction ofmove" and setting the delay for the speed. J is the positionof the cursor, I for the target. Line 105 is to clear thescreen, but the clear screen character is not reproduced bythe printer.

200 GETA$210 1FA$ =""THENGOT0260212 1FA$ ="S"THENGOT0500213 IFA$ ="N"THENGOTO900215 POKEJ,SS220 FORK =1T08230 IFA$ =B$(K)THENJ =J +C(K)235 NEXT K240 IF J>33767THENJ =J -40250 IF J <32768THENJ =J +40260 POKEJ,YY

Moving the cursor; the direction depending on which keywas pressed - the main action takes place in the loop onlines 220-235. Lines 240 and 250 stop you from going offthe top and bottom of the screen.


Stomper

NIT I1 xNITS

-401-

265 IF RND(TI)>DF THEN 200270 X =RND(TU271 POKEI -41,32272 POKEI-40,32273 POKEI -39,32274 POKEI -1,32275 POKEI,SY276 POKEI +1,32277 POKEI +2,32:POKEI +3,32278 POKEI +39,32279 POKEI +40,32280 POKEI +41,32281 IFX <.25THENI =1-40290 IFX >.25ANDX <.5THENI =I-1300 IFX >.5ANDX <.75THENI =I +1310 IFX >.75THENI =I +40320 IFI >33767THENI =1-40330 IFI <32768THENI =7. +40340 POKEI,MM341 POKEI -41,77342 POKEI-40,66343 POKEI-39,78344 POKEI -1,87345 POKEI +1,64:POKEI +2,64:POKEI +3,64346 POKEI +39,78:POKEI +40,66347 POKEI +41,77350 GOTO200

Moving the target; the speed delay takes place at 265.Lines 271-280 blank the target, lines 281-330 move thetarget and lines 340-350 restore the image on the screen.

500 IFI =JTHENGOTO600510 POKEJ,YY:POKEI,MM520 PRINT" MISSED"

65

ETI Softspot Stomper

521 MX=MX+1522 PRINT" ";100*(N/(N+ MX+ 1E- 30));"%HITS"523 FORKK =1T01000:NEXTKK525 PRINT""530 GOT0270600 N =N +1605 POKEI-2,19:POKEI-1,16:

POKEI,12:POKEI+ 1,1:POKEI+ 2,20606 POKEI -3,64610 PRINT" HIT";N613 PRINT" ";100*(N/(N+ MX+ 1E- 30)):

"%HITS"614 FORKK =1T01000:NEXTKK615 PRINT""616 J =32768620 GOTO200

The test for a "hit" (the position of the cursor and theposition of the target coincide) is made at line 500. If theydon't a message is displayed which is kept on the screenfor the duration of the delay at line 523. The game thencontinues from where it was left off. If a "hit" has beenscored then again a message is displayed, but the cursorposition is reset (line 616) before continuing.

700 PRINT "THE OBJECT OF THE GAME IS TO`STOMP' "

710 PRINT "ON THE INSECT. TO DO THIS YOUMUST"

720 PRINT "MOVE YOURSELF (WHITE) OVERTHE INSECT'S"

730 PRINT "BODY AND, ONCE OVER IT, PRESSTHE"

740 PRINT " 'S' KEY. THE INSECT, HOWEVERDOES"

750 PRINT "NOT STAY STILL: THE SPEED IS SETAT"

760 PRINT "THE START OF THE GAME TO AVALUE OF"

770 PRINT "BETWEEN 1 AND 10. TO MOVEYOURSELF"

780 PRINT "USE THE NUMBER KEYS (1-9, BUTNOT 5)"

790 PRINT "`N' RESTARTS THE GAME AT ANYTIME"

800 PRINT "PRESS ANY KEY TO START"810 GET A$820 IFA$ ='"`THENGOT0810830 GOTO5900 N =0: MX =0950 GOT010This displays the instructions. The lines, along with lines1-4, can be omitted if the facility is not required.

a

NIIMICII

0 It NITS

. *--.g . The program leaves plenty of room for improvement, andnot only in its logical structure. The scoring system couldeasily be made more imaginative, for instance, and theintricacy of the game increased - a suggestion is to havethe insect slow down if a leg is stomped off.

Geography test programThe program shown will test the geographical knowledgeof the user.

The program will first prompt with a request for thearea of the world that will be tested - options are Europe,South America and Asia. After this the machine willprompt with a request that the user enters the name of thecapital city of one of the countries within the chosencontinent. After ten questions the computer will show thescore for the session and enquire whether or not the userwishes the test to continue.

The program was written for TRITON but should besuitable for implementation on most small BASIC sys-tems.10 PRINT "GEOGRAPHY TEST-CAPITAL

CITIES"20 LET R =0,W =030 PRINT40 PRINT "1.EUROPE 2.SOUTH AMERICA

3 .ASIA"50 PRINT60 INPUT "PLEASE TYPE NUMBER OF CONTI-

NENT CHOSEN" A70 IF A =1 GOTO 10080 IF A =2 GOTO 18090 IF A =3 GOTO 260

100 PRINT110 FOR I =1 TO 12; at(I)=0; NEXT I120 FOR L =1 TO 12130 PRINT140 PRINT "WHAT IS THE CAPITAL OF"; GOSUB

340150 GOSUB 500; INPUT "THE ANSWER IS

NUMBER" B; GOSUB 910160 NEXT L


Shortwave World Record That DX

Record That DX

John Garner discusses the convenience of taping your receiving sessions.

FOR THE SERIOUS DXer, a modestbut functional tape recorder can provean invaluable asset to his listeningactivities. A recorder is very useful forthe shortwave listener in that he canreplay broadcasts and gather exactinformation for reception reports. Thefacility to replay a broadcast a numberof times can mean the difference inbeing able to identify stations receivedwith considerable interference orbroadcasts in a variety of foreignlanguages. This replay facility alsoallows the listener to note suchpertinent facts as announcer names,program names, and specific wordingof station identification.

DXers enjoy sharing their receptionexperiences with fellow DXersand non -listeners alike. A recorder will allow theDXer to build a basic library ofbroadcasts which he can replay for hispersonal enjoyment and the enjoymentof others.

THE MACHINE:A number of articles have been

written advocating the reel-to-reelrecorder as the most useful format forthe SWL. However, Don Dawson, ofAlberta, who has had over 15 yearsexperience with the use of homerecording equipment, has found thecassette recorder to be much moreversatile. I must agree with Don and Ihave used several cassette recorders inmy listening room. Quality tapeavailable in the cassette format isconsiderably less expensive than reel-to-reel tape of an equivalent quality.The compact format of cassette makethem ideal for storage purposes and formailing recorded material. It alsoallows one to remove a recording fromthe machine without having to rewindthe tape. The knock -out feature ofcassettes ensures that valuablerecordings will not be accidently

erased. The cassette recorder itself isalso a nice compact size.

In selecting a cassette recorder, thefirst decision that the SWL will be facedwith is whether to buy a portable or astereo cassette deck. Although the costis definitely higher for the stereo deck($125 -$175 as opposed to $60 - $100)it is recommended. A number offeatures which are useful to the SWL areonly found in the deck models. Thestereo feature will allow the user to

his DX activities.If you have two receivers the stereomodel will allow you to record the timefrom WWV or CHU on one channel asyou record the program on the secondchannel. This would allow you to havethe exact time of program details to aidyou in your reception reporting.

The following is a list of featureswhich the listener will find useful in hisrecording activities:Automatic Recording Level: Thisfeature is extremely useful in that it willtend to compensate for fluctuatingrecording levels due to fading. Thisfeature should be switchable to allowfor manual level control which is

preferable when recording music.Digital Tape Counter: This provisionwill allow the listener to note criticalpoints in broadcasts when IDs aregiven, frequencies listed and intervalsignals are played. It also allows you tofind a particular portion of the tapequite rapidly.Pause Control: This function is usefulfor editing recordings the listener maywish to keep and for momentarilystopping the tape when making writtentranscriptions.Automatic Full -System Shutoff: Withthis provision the listener can leave therecorder unattended and it willautomatically stop at the end of thetape.

Microphone/Auxiliary Input Jacks:Both these jacks have a significantbearing on the type of receiver therecorder can be connected to. This willbe discussed further later.Headphone Jack: This facility is

extremely useful in transcribingbroadcasts where reception quality ispoor. What may sound like hash whenplayed over a speaker may prove to bemuch more readable over headphones.Also headphones are good for late hourlistening without disturbing the rest ofthe household.Dolby Noise Reduction: Wh Ie thisfeature is not essential it will certainlyenhance the quality of musicalrecordings and will assist in cuttinghigh frequency noise on somebroadcast recordings.Frequency Response: This area is notcritical for DX recording as even thebottom -of -the -line recorders have anadequate frequency response forbroadcast recording. If the machine willalso be used for music recording it isrecommended to have at least afrequency response of 30 - 15000Hertz with Chrome or Ferri -Chromecassettes.

THE TAPE:With the growth in popularity of

cassette recorders over the past dozenyears or so there are literally hundredsof different brands of cassette tapesavailable. Unfortunately, many of thebargain priced tapes are highlyuiacceptable in terms of bothmechanical and recording quality.From a mechanical point of view, agood cassette should operate smoothlyand quietly in all tape movementmodes. The shell of a good cassette isusually held together by four smallscrews rather than by glue. The tapeitself should be relatively low inbackground hiss and free from


Shortwave World

dropouts (ferrous oxide inperfectionswhich cause blank spots in recordings).Cassettes marketed by the leading taperecorder manufacturers areconsistently good quality buys. Tapesproduced by the manufacturer of arecorder are designed to complimentthe machine's capabilities and are aworthwhile investment, especially forgood musical reproduction.

There are a number of differentclasses of cassette tapes on the market.The top -of -the -line Ferrichrome andChrome tapes are best for recordingmusic if the cassette machine has theappropriate bias and equalizationsettings for them. Tapes in the "HighFidelity" and "Low Noise" categoriesare in the middle price range and are ofsufficient quality for broadcastrecording. Standard or budget -pricedtapes tend to be high in backgroundnoise and are unsuitable for mostrecording applications.

Cassettes are available in a range oftime -lengths from 15 minutes per side(C-30) to 60 minutes per side (C-120).From practical experience the C-90 (45minutes per side) is most useful for SWrecording. The 45 minute time spanallows one to start the machine a fewminutes before a broadcast is due tostart and still allows a sufficient timemargin to record the closingidentifiation at the end of the program.While the C-120 cassettes offer evengreater recording time, they arecomprised of extremely thin recordingtape and have been known to bind orjam easily. The C-30 tapes are ideal forkeeping recordings of interval signalsor excerpts from favorite broadcasts.

EQUIPMENT OPERATION:There are a number of different ways

to connect a cassette deck to a receiver.If your receiver is equipped with a taperecording output jack you simply usedthe appropriate patch cord to connect itto the auxiliary (sometimes called Line)input jack of your cassette recorder. Insome cases the cord may have to beconnected to the microphone inputjack to provide sufficient recordinglevel (read both the recorder andreceiver manuals to determine therecommended procedure). Thismethod is the most ideal means ofinterconnection in that the recordingsignal isnot altered by receivergain andattenuation controls.

Unfortunately, the provision of arecording output jack is a relativelyrecent innovation on the part of receivermanufacturers. If your receiver doesnot have a record output jack, there arethree different ways in which it can beconnected to a recorder. The simplest

68

John Garner's hand activates his cassetterecorder as he awaits an exciting broad-cast from Radio Tahiti.

and least expensive method isto place amicrophone in front of the speaker.This method is almost totallyunsatisfactory as the recorded audioquality will be very poor due to themicrophone picking up all extraneousroom noise as well asthe speaker audio.The second method is to use a patchcord with alligator clips on one end anda plug that matches the recorder onthe other end. The alligator clips areattached to the speaker lugs of thereceiver and the plug is inserted in theAux/Line input of the recorder. Whilethis method will eliminatethe recordingof extraneous room noise, the signal isstill influenced by receiver Gain andAttenuator controls. The speakersignal from the receiver is very strongcompared to conventional recordingoutputs and resistors may have to beused to cut the signal power down fortape recorder input. The most suitableand most expensive method is to takeyour receiver toa competent technicianand have a recording output added tothe circuitry.

It is strongly recommended thatlisteners should keep their recordersrunning whenever they are tuningaround the bands. You never knowwhen you may run across that hard -to -catch station and you may miss gettingthe interval signal or sign -on remarks ifyou have to fumble around loading atape and starting the recorder.

If you are planning on building alibrary of DX recordings it's useful tohave access to a second cassetterecorder. In this way you can edit your

tapes and make up short representativesamples of programs you have heard.

Some of the latest additions to thecassette recorder market feature aprovision for connecting the recorderto a timer. This may be useful for thosewho prefer a good night's sleep tonocturnal DX -chasing. It also enablesyou to record a program when you areunable to be present at your radio.

So add a recording mode to yourlistening operation and add a wholenew dimension to your enjoyment ofthe hobby of shortwave listening.

Thanks to Don Dawson who suppliedmost of the material for this article.

SHORTWAVE MAILBAG: P.O. Box142, Thunder Bay, Ontario, P7C 4V5

Gordon Penn of White Rock, B.C.asks for the length of a long wireantenna for each of the shortwavebands from 10 to 120 metres. -A longwire antenna, no matter how long, willwork satisfactorily on most bands.Usually 75 feet is quite a good length.For improved reception on a specificband an antenna cut for that band willyield better results. To find the requiredlength for a half -wave antenna simplydivide the metre band by 2 and you havethe length in metres. To convert to feetsimply multiply by 3.28. Thus a half -wave antenna for the 120 metre bandwill be 120 2 x 3.28 or 196.8 feet. Thelength for the 10 metre band wouldwork out to 16.4 feet. Other bands inbetween may be figured out in the samemanner.

ANARC '79 CONVENTION:The 1979 Convention of the

Association of North America RadioClubs (ANARC) will be held on theweekend of June 22, 23, 24, 1979 at theRadisson Downtown Hotel inMinneapolis, Minnesota. Among theinternational broadcasters who will beattending the convention are BobZanotti of Swiss Radio International,Jonathan Marks of Austrian Radio andIan McFarland of Radio CanadaInternational. The convention is openfor all shortwave listeners whether youare club members or not. So come toMinneapolis for a great weekend andmeet others interested in this hobby.REALISTIC DX -300

Radio Shack have recentlyintroduced a new receiver on themarket, the DX -300. I had a chance tohave a look at this set the day it arrived ata local Radio Shack store and wasquiteimpressed. The circuitry and controlshave led me to believe that this receiveris manufactured for Radio Shack bytheYaesu-Musen Co. (the makers of theFRG -7 and FRG -7000). There isjust too


Record That DX

much similarity between the DX -300and the FRG -7 for coincidence.

The DX -300 Quartz -SynthesisedCommunication receiver covers 10 kHzthrough 30MHz, and is able to receiveAM (Amplitude Modulation), CW(Continuous Wave) and SSB (SingleSideband) signals.

The synthesized drift -cancellingtriple -conversion mixer systemprovides thirty tunable ranges form 10kHz to 30 MHz and is derived from asingle 4 MHz quartz oscillator. Thisaidsfrequency control and stability. Astable low frequecny "kHz tuningcircuit" covers the 1MHz incrementsand the 5 -digit display shows the exactfrequency.

The DX -300 uses 37 transistors (10 ofwhich are field-effect type), a Large -Scale Integration IC frequencycounter, 3 integrated circuits, 25diodes, 5 seven -segment LED displaysand six LEDs.

You can use the DX -300 at home (on120 volts AC or 12 volts DC -8"C' cells)or in your car or recreation vehicle (12volts DC negative ground).

A six element ceramic filter providesoutstanding selectivity (freedom from

,A141111111.101AN: 4414111MININIMONIMIP ill11111111111111011111111111166.

Radio Shack's super -receiver, the DX -300.

adjacent channel i nterf erence), while adual MOS Field-effect transistor is usedin the critical mixer stage (freedomfrom cross -modulation andundesirable RF distortion).

The DX -300 sells in Canada for$499.95. Dimensions of the receiverare

All in ETI's 741 Cookbook:

V

146 mm high x 362 mm wide x 252 mmdeep and it weighs 6 kilograms.

Next month I will have someinformation on other Radio Shackreceivers. Until then, 73 and goodlistening.

Differential voltagecomparator

Open -loop inverting DCamplifier

Closed -loop inverting DCamplifier

Non -inverting DC amplifierUnity -gain DC voltage

followerX100 inverting DC amplifierVariable gain inverting DC

amplifierHigh impedance x100

inverting DC amplifierX100 inverting AC amplifierNon -inverting x100 DC

amplifierNon -inverting variable -gain

DC amplifierHigh input impedance,

non-inv, x100 AC amplifierNon -inverting x100 AC

amplifierDC voltage followerAC voltage followerVery high input impedance

voltage followerUnidirectional DC v -follower,

boosted outputBidirectional DC v -follower,

boosted outputUnity -gain inverting DC adder

(audio mixer)Unity -gain balanced DC phase

splitterUnity -gain differential DC

amplifier (subtractor)Semi -log AC voltage amplifierConstant -volume amplifier1kHz tuned amplifier

(twin -T, acceptor)1kHz notch filterVariable low-pass filterVariable high-pass filterVariable -voltage supplyStabilised power supplyStabilised power supply with

overload protectionPrecision half -wave rectifierPrecision half -wave AC/DC

convertorDC voltmeter converterDC voltage or current meterPrecision DC millivoltmeterPrecision AC millivoltmeterLinear -scale ohmmeterAudio Wien -bridge oscillatorSquare -wave generatorPrecision temperature switch

Available from ETI for $2 (includes postage). Justorder our May 1977 issue from ETI Back IssuesDept, Unit Six, 25 Overlea Blvd, Toronto, M4H 1B1.

eti PANEL TRANSFERS

A really high qualitysystem for finishing offyour projects. The sheetsinclude a mass of letteringand control scales forboth rotary and linearpots.

The lettering is trans-ferred simply by laying onto the panel and rubbingdown - it's strong andpermanent.

fi '1 1 1 1 '1 1 1

7

The markings are ontwo sheets (a full-sizedone cut in half for easypostage) and containsufficient lettering fordozens of projects.

Send $3.50 (includingpostage) to ETI PANELTRANSFERS. Unit Six, 25Overlea Blvd., Toronto,Ontario, M4H 1B1.Ontario Residents addPST.

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REPLACEMENT PICTURE TUBESFamous Super Chromacolor ® picture

tubes in a range of sizes to replace atotal of 80 industry types. PlusSunshine® and Cinebeam picturetubes to fit almost any brand of color

TV. And Zenith black & white picturetubes to replace 401 other types of B & W tubes.

ZENITH QUALITY PARTSAll the parts you need, from bel fuses

to TV knobs. The star is the ZenithInstant Parts Program (ZIP). It putsthe 100 most used replacement partsat your fingertips, in a specially

designed, compact rack. ZIP makesinventory and re -ordering fast and easy for you.Also, Zenith now offers a line of capacitors, resistors,integrated circuits and universal semi -conductors anda full line of universal needles and cartridges.

Mayor Appliances Div.,Acklands Ltd.,1725 Quebec Street,Vancouver, B.C.Phone -1-604-879-4631

For quality you can depend on.in replacement parts and accessories -

all in one convenient place

B.R.E. Electric Ltd.,5544 -5th Street S.E..Calgary, Alta. T2H 1L3Phone -1-403-253-7171

Your Zenith Distributorhas the parts andaccessories you need inone convenient placeyour Zenith One -StopShopping Center.

REPLACEMENT RECEIVING TUBESA complete line of more than 1,000

Zenith quality tubes . . . the sametubes as used in Zenith originalequipment. Built to operate withgreat reliability - to cut your callbacks.

And they have the long life neededto increase the satisfaction of your customers.

ZENITH QUALITY ACCESSORIESHere are just a few! Quad, stereo and

monaural headphones. Broadened lineof outdoor antennas featuring 13 all -newSuper Chromatenna models. Completenew Chromatenna indoor antenna line.

Antenna rotors. Three grades of batteries ina wide range of sizes. Electronic chemicals, including tunerdegreaser, tuner cleaner, circuit cooler andtape head cleaner. CassPtte and 8 -track recording tapecartridges and record care products. A full line of testequipment & service aids.

Beside parts and accessories, your Zenith Distributorhas the specialized "know how" to help solve toughservice problems. Come in or phone today.

YOUR LOCAL ZENITH DISTRIBUTOR:

B.R.E. Electric Ltd.,14840 -115th Ave.,Edmonton, Alta. T5M 3C1Phone -1-403-455-7171

Major Appliances Div..Acklands Ltd..1155 Sherwin Rd..Winnipeg, Man. R3H OV1Phone -1-204-633-6679

Zenith Radio Corporationof Canada Ltd..1020 Islington Ave.,Toronto. Ont. M8Z 555Phone -1-416-231-4171

Zenith Radio Corporationof Canada Ltd.,900 Boul St. Martin 0.,Chomedey, Lay. POH7S2B6Phone -1-514-663-0430

Waldale Limited.Station Street. Box 339,Amherst, N.S.Phone -1-902-667-3308

get* ore,/Pq ast koc. <?r,;.,6,

(//:r "2'°eci /??C) rit 6`, %/7t 41`.9

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Dick Cartwright covers the C E A S A, which is rapidly becoming better known,and attracting more members.

AS PROMISED in the previouscolumn Ihave devoted most of the last 2-3 weeksto researching the origins and goals ofCEASA (Canadian Electronic &Appliance Service Association). Mr.Bill White, the General Manager, mostkindly supplied me with severaleditions of their quarterly publication,Service Contacts, and the most recentedition of their monthly news bulletin.These contained a wealth ofinformation.

This Association was founded sometwo years ago by a group of concernedmanufacturers, importers and retailers;Canadian Admiral, the T. EatonCompany. Electrohome, Simpson -Sears, Sony, to name just a few. Theaims and objectives of the Associationcan best be summed up by quotingverbatim a letter written by Mr. K. R.Allen, the first President. This letter istaken from the first issue of ServiceContacts and outlines very well theobjectives of this very down-to-earthnational association.CEASA BACKGROUND

"For many years, representatives ofthe major servicing companies andservicing operations of importers,distributors and retailers were invited toattend the Service Committee Meetingsof CAMA, CEMA and latterly EEMAC. Itwas a friendly relationship but a difficultsituation since representatives frommany of the major service operationsattended the meetings as observers, byinvitation only. Imagine, the CanadianElectronic and Appliance Serviceindustry is a four hundred milliondollara year business and some of the largestservice operations did not have a singlevoice in the formation of policy,government legislation, consumerrelations, etc. This situation was of

great concern to many, includingmembers of CAMA, CEMA, EEMAC, aswell as importers/distributors, likeSony and Hitachi, and nationalretailers, like Eatons and Simpsons-Sears. A seed was sown, however,something had to be done to bring ALLof the Canadian Electronic andAppliance Service Industry into oneassociation.

"It took two years for the seed todevelop and the result is the CanadianElectronic & Appliance ServiceAssociation, incorporated underfederal law. An entity at last A voice forService in the marketplace!

"But why CEASA? The Aims andObjectives tell it all! The "Code ofEthics" puts it all in order! AND NOWTHE WORK BEGINS. Putting togethera National Association representing'consumer oriented' serviceorganizatons, from British Columbiato Newfoundland, all dedicated to oneoverall objective - consumersatisfaction. Working together, greatthings can happen and when consumeracceptance and trust has been built up,the consumer will, rightly, look uponservice as an 'assurance of value' and'peace of mind' in the Canadianmarketplace. That's a good part of whatCEASA is all about."

AFFILIATIONSSince its formation a number of

provincial associations have affiliatedthemselves with CEASA, and again I

would like to quote an excerpt from thesecond edition of Service Contacts:

"PROVINCIAL SERVICE ASSOCIA-TIONS ARE ON THE MOVE: Thepast history of electronic/applianceservice in Canada has been onewith little organization or associa-tion. Over the last five years, however,

6, e*: ali j0

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service technicians and businesseshave gathered together in severalprovinces across this fair land toform associations or guilds. CEASAproudly counts three ProvincialAssociations as members, is assistingin the formation of three more and istalking about affiliation with two others.Readers interested in membershipshould contact the association in theirprovince as listed

'Appliance Service Association of B.C.,860 Kingsway, Vancouver, B.C. V5V 3C3Mr. D.W. Loughran, Secretary.Ellectronic Guild of B.C.,735 Sixth Street, New Westminster, B.C.V3L 3C6Mr. George Quan, President.'Professional Electronic Guild of Alberta,P.O. Box 784, Stony Plain, Alta.Mr. R.A. Hopkins, President.'Manitoba Electronics Service Association,297 St. Mary's Road, St. Boniface, Man.Mr. M. Wrublowshy, President.New Brunswick Electronic TechniciansAssociation,247 Dundonald St., Fredericton, N.B.Mr. Glen Smith, President.*CEASA Provincial Members

''Taking an active part in a ProvincialService Association is a goodinvestment in many ways. It gives youthe opportunity to meet othersinterested in the same business, sharethe same concerns and experiences,exchange ideas and come up withsolutions to everyday situations. Themembership fee to belong to a

Provincial Service Association is notonly tax deductible but also yieldsmuch richer returns in knowledge,experience and future planning.

"Make a point to invest in your futureby becoming a member of yourProvincial Association."


Service NewsSERVING CANADIANSFOR OVER 25 YEARS

UHF VHF FMVARACTOR TUNERSSolid State our SpecialityWe service more TV Tunersthan all other tuner compan-ies combined.We also service all makes ofTV cable convertors.

a

CASTLETUNER SERVICE

24 Cranfield Road,East York. Toronto M4B 3H1

Tel 752-7330/1

OURSREALLY WORK!

Between March 1978, whenwe introduced direct -etchPCB transfers to Canada, andMarch 1979, tens of thous-ands of sheets of CERESISTbrought joy to electronicsnuts. And/or bolts.

We've received a raft ofcompliments, but NOT ONESINGLE COMPLAINT con-cerning product quality andperformance.

Isn't it nice to know that,in this 'best? of all possibleworlds,' one thing (besidesyour own immaculate mind)is perfect?

onn000sends.a.e. ceresistfor info nonoo

dealersinvited

CERES, 53 Burnett Ave.,Willowdale, Ont. M2N 1V2.

On March 8th in Toronto CEASA, attheir Annual Meeting, elected a newBoard of Directors forthe 1979-80term,who in their turn appointed thefollowing Executive Committee toconduct the business affairs of theAssociation: Chairman and ChiefExecutive Officer- N.A. Stewart, InglisLtd.; President - A.G. Brooks, T. EatonCo. Ltd.; Vice -President - Retailers -K.R. Allen, Simpson -Sears Ltd.; Vice -President - Electronic Manufacturers- J. Leitmann, Sony of Canada Ltd.;Vice -President - ApplianceManufacturers - D. Good, CanadianAdmiral Corp. Ltd.; Vice -President -Finance - W.C. Bradbury, GSW HomeService; Vice -President - ProvincialMembership - R.A. Hopkins,Professional Electronics Guild ofAlberta;

Heartiest congratulations to thismost imposing Board of Directors.

(Permission to reprint any part of,

tCARD

AUTOMAT ICCASH

Cisco.

facts or figures, from Service Contacts,CEASA's official quarterly publication,has been granted by Mr. W. A. White.)

My discussions with the GeneralManager of CEASA left me with afeeling that this Association shouldquickly attain its objective, aspreviously stated, of coast -to -coastrepresentation through affiliatedprovincial associations. They have a loton the ball!

Inquiries re CEASA should be directto: Mr. W.A. White, Canadian Electronic& Appliance Service Association, Suite804 - 45 Wynford Heights Cres., DonMills, Ont. M3C 1L3

Thanks, CEASA! For the first time Ifeel I now have a source of service newswhich is not just provincial in scope butis nation-wide.All the best.

Richard H. Cartwright.


Q31_3K QRM

Bill Johnson, VE3APZ, talks about what wasn't done about split -splits, andhimself, amongst other interesting (to him at least!) topics.

SPRING IS SPRUNG, the grass is riz,I wonder where the birdies is? It'sa pity that you won't be reading thisuntil the summer, but I just had to getit out of my system. Now is the timefor antenna work, hamfests, hamfests,club picnics, mobile rallies, and publicservice events, and another round ofhamfests for good measure. Still, wehams don't need events like these toget to know each other - we have theprivilege of using the ether waves toaccomplish this. Which has led me todiscover one thing... I am almost un-known west of Thunder Bay. SinceI don't stand around the magazineracks in Stores autographing copies ofETI west of Mississauga, and I don'tget on the Transcanada net, the abovefact is not surprising. Naturally, every-body in Toronto has heard of me. I

have moved around so much that I

have lived near and been a memberof every Metro Toronto area radioclub of note for at least one year.Since I haven't been on the shortwave bands for almost a demi-decademost of the people I talk to have beenon six, two, and 450 MHz. So I'm notsurprised that the only fan mail I getis from Ontario. The opinions I ex-press are those of an Easterner. That'snot the way I want it, because ETI isa Canadian magazine and is read allacross Canada. While I try to speakfor the amateurs of Canada it is verydifficult for me to voice the opinionsof those out west if they don't let meknow what they are. To help youall out there build a mental pictureof me, I've decided to give a briefdescription of myself. I've been licens-ed since 1969, hold all three CanadianCertificates, but don't use the privilegesafforded me by at least two of them.For the last five years my amateuractivity has been all VHF/UHF, and

has focussed around repeaters ownedby the Toronto FM Society, of whichI have been a Director for five years.I have somehow managed to get intomicrocomputers, which is somewhatlike taking your job home, since I workas a Computer Technician. (amongstother things).

That's enough about me. Pleasevote for me in the next election etcetc. Now that you realise that I'm anFM, nob maybe you'll understand whyI write about VHF and repeaters a lot.It used to be people on FM were re-garded as a bit 'funny'. As we put upmore and more repeaters, and moreand more people flocked to use them,it became an accepted thing. Noweverybody has a 2 metre rig - at leastin their car. Again we are faced withanother example of lack of commun-ication in this country of ours. In thebeginning, we had repeater channelsevery 60 kHz from 146.1 to 146.46.We then put extra channels half -wayin between them and added inverted30 kHz channels above 147 MHz.As crowding grew and the equipmentbecame good enough to accept it,natural evolution said we should splitthe 30 kHz channels into two and goto 15 kHz "split -split" channels. Toconfuse matters more, these 15 kHzchannels were "inverted" meaning that,for instance on a frequency below147 MHz you would transmit high andreceive 600 kHz lower instead of thelow transmit - high receive orientationof the rest of below -147- land. Thesechannels became known as the "invert-ed split -splits" or "tertiary" channels.Well, strangely enough, despite plan-ning, these new 15 kHz channels werefound to be too close for comfort inhigh density areas. A repeater operatingat too wide a deviation would open thesquelch of another repeater whose input

was only 15 kHz away from the form-er's output. The system was designedfor ideal conditions.

I heard a voice crying in the wilder-ness, but nobody listened. The voicewas saying "Stop - before it is toolate - go to channels every 20 kHzinstead of 15 - this will reduce inter -mod, remove the need for invertedchannels, and make modification ofexisting synthesizers unnecessary.(Many models need an extra switch togo on a 15 kHz boundary). This voicecame from Vancouver. It went unheardin the East. 15 kHz split -splits were"in". Motion carried unanimously.Some communicators we are!LESSON OF THE MONTH

Q. "I want to put a 110 foot selfsupporting tower in my garden, witha 5 element beam for 10-15-20 metres,stacked 15 -element yogi's for 450, anda J-Beam for two. My local townshipwon't give me planning permission.What can I do?

A. First of all, to to your locallibrary. Get a copy of the OfficeConsolidation of the Radio Act, andthe Radio Regulations parts 1 & 2.In the back you will find engineeringdata on the construction of antennas.If your proposed antenna meets theserequirements, then there is not a lawon the books in any province or munici-pality in Canada that can prevent youputting up that antenna. If it doesn'tthen the proposed antenna is classifiedas a "dangerous thing" and the localmunicipality or city, if appointed bythe Federal government, can preventits construction or demand its repairto the standards.

This is due to a uniquely Canadianlegal loophole known as "FederalJurisdiction", which works like this;in a field where there is a Federal lawapplying, which is also proven to be


QRM

a matter of Federal jurisdiction byprecedent then no authority in Canadacan pass a valid law which limits theFederal law. Since there is a Federallaw on antennas, and radiocommun-ications is Federal jurisdiction, thenyou are safe in putting up your antenna,provided that it complies with theFederal law. (which doesn't mentionanything about zoning or planningby-laws).ORM LETTERS

Either nobody wrote to us, or thepostie is still away sick with the herniathat he got delivering last month'sletters. Either way, we got not mail,so I'll have to rely on word of mouth.

Again, since you guys out West havelittle chance to talk to me on 2mFM,you'd better write to get your fairshare

The thing that people mention mostis their support for my views on theRSO repeater issue. It seems that allthose who have criticized them mis-understood my views, so here they arein simple -to -understand one -liners: --1) Southern Ontario does not need2) Morse code practise is fine, but

another 2 metre repeater, especiallya wide -area one.

let's not spoon-feed students. If theycan't put up a decent antenna to re-ceive W1AW or, perhaps VE3RSO on80 metres, then they won't survivelong as amateurs.J) If the RSO is going to do anylinking between repeaters, it has to beon 220 MHz or above. That was whatwe told the D.O.C. in 1971 and thatis what they made their official policy.If the RSO violates the spirit of thelaw then it will become the letter ofthe law. That's all I have to say on thematter. 73 till next month.

It is with deep regret that we record thepassing of Don Green VE3HDV onApril 15th, at the age of 39.

In 1966 Don was involved in acrippling auto accident,and despiteoperations and continuous care, hebecame extensively paralized. He be-came an amateur in 1972, although attimes it was difficult for him to use theradio. Amateurs who knew him only onthe air would never have guessed this,

BINDERS

since he was very willing to help out bymaking a phone call or relaying amessage to another ham.

He was formerly a member of theScarborough Amateur Radio Club, and,more recenyly, of the South PickeringAmateur Radio Club. His membershipin the Toronto FM Society never lapsed,neither did his participation in thepublic service events such as the Canad-ian Winter Car Rally. As well as main-taining a full HF & VHF schedulefrom his hospital bed, he spent count-less hours phoning blood donors for theRed Cross. This tremendous attitudetowards his fellow man is exemplifiedby one of his last wishes - that hisequiptment be available for loan to anyneedy amateur. Anybody knowing of adeserving candidate should contact:Brent Davis, VE3EJW, Cherry wood,Ontario,LOH 1CO.

Don will be sadly missed by allhis friends on the air, especially onVE3 RPT and VE3OSH repeaters, ONT-A RS and the ROAD RUNNERS nets. Amemorial net held on VE3 OSH onWednesday April 18th received wellover sixty check -ins.

In response to many requests from our readers we havearranged for binders to be made so that you can keep ETI'sfirst volumes together and protected from damage. Thebinders are covered in attractive leather -look black plasticand are designed to hold twelve issues. The ETI design isprinted in gold letters on the spine.

The binders cost $6.00 each, which includes postage and packaging. Do not send cash - you can pay by cheque. Mastercharge, or ChargexCredit card orders must include your account number, the expiry date, and your signature. In all cases allow six weeks for delivery.

Send your order to ETI Binders, Unit 6, 25 Overlea Blvd., Toronto, Ontario M4H 1B1. Don't forget to include your name and address.Ontario residents add 7% PST.


Tech TipsTech Tips is an ideas forum and is not aimedat the beginner. ETI is prepared to considercircuits or ideas submitted by readers for thispage. All items used will be paid for. Drawingsshould be as clear as possible, and the textshould preferably be typed. Circuits must notbe subject to copyright. Items for considera-tion should be sent to ETI Tech Tips, Unit 6,25 Overlea Blvd., Toronto, Ontario, M4H 1B1

Q1 C22N1184 470n

1- OUTPUTLS 1

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COMMON

S WI GROUNDMicrophone Speaker

J. SmithWhat do you do if you need amicrophone in a hurry - the shopsare closed and your friends are onholiday? Or you are just a little short ofmoney? The answer is to build thefollowing circuit from your odds andends box. This circuit uses a smallspeaker as a microphone, one tran-sistor and only four other parts, drawsonly about 2 mA of current from a 9volt battery so an on /off switch is notreally necessary.

The transistor shown is 2N1184and is a PNP germanium mediumpower type but is not critical - try theones you have first before buying thisnew type. The components too are notcritical and the prototype was found towork OK with 20% variation invalues. The output is high impedanceand is fed into the mic input of a taperecorder or pick-up input of anamplifier.

+12

RI1K

C.B. oPOINTS o

Speed Alarm

D. Ian

It is all too easy, during a long journeyon a motorway, to allow one's speedto gradually creep beyond that pointwhich the boys in blue take an un-welcome interest; this alarm gives anaudible nudge whenever you driftover a pre-set speed.

Pulses from the distributor points(due to the ignition coil up to 400Vmay be developed as the points open)are passed through a current limitingresistor, rectified and dipped at 4V7.Via Q1 and the diode pump a DCvoltage, which is proportional to en-gine revs, is presented to RV1; thesharp transfer characteristic of a'CMOS gate, assisted by feedback, isused to enable the oscillator formedby the remaining half of the 4011.

At the pre-set 'speed' (revs) a non -

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ignorable tone emits from thespeaker, and disappears as soon asthe speed drops by three or four mph.

Calibration of Ca may be con-ducted with an accurate pulsegenerator remembering that, for afour stroke engine, frequency = revsper minute times the number ofcylinders divided by 120; for a carwith a specification of 171/2 MPH per1000 revs, in top gear, f =133Hz at70 MPH, 124Hz at 65 MPH (4000'RPM and 3714 RPM). The necessaryfrequency should be fed to Q1 andVR 1 set so that the alarm is just off.Reliable switching occurs on the pro-totypes with a change of only 5Hz(1 50 RPM), ie less than 3 MPH for theabove example.

Direct calibration 'on the road',while covering discrepancies due totyre size, etc, will only be as good asthe speedometer and obviouslyshould be carried out by a passengerrather than the driver.

Ill ED mgIC 1

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Tech Tips

are

approx. 12V

3306012N3904

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LED

0

Micro-Digi Car ClockD. Ian

TOUCHCONTACTS

TO

With the availability of economicalLCD wristwatches has come a surplusof very cheap LED types which, with alittle ingenuity, are eminently suitablefor a permanent display installation;one obvious use is a cheap digital carclock.

The majority of these timepiecesuse two silver oxide cells in series togive 3.2 volts; current consumption,with the display on, is rarely morethan 30 mA, easily provided by asimple stabiliser circuit.

Remove the back of the watch -caseand discard the cells; the contacts ofone cell holder are shorted togetherand the 3V2 supply soldered, notingpolarity, to the two remaining con-tacts: with the 'display on' switchshorted out the result is a highlyaccurate mini -clock with negligablecurrent drain as long as the vehicle isin regular use; even 35 mA will even-tually flatten a car battery thatreceives no charge. Most simpleLED watches have a brass tag,bearing on the metal case, as a com-mon terminal to the various controls,these generally being spring loaded

1001

10M

1M

6

5

3

10

12

IC CD4066

3.2V

TOWATCHMODULE

7.1::11SPLAY'SWITCH

0v

pins pressed, as required, into contactwith clips on the perimeter of themodule. These connections can beextended to panel mounting pushswitches, allowing the unit to behoused in a suitable box.

If the car is used infrequently it isprudent to arrange for the display toautomatically extinguish at the end ofa fixed amount of time; this also'implies the simplest possible 'on'switch to minimise loss of attentionwhen driving. One half of a CD4066quad bilateral switch is connected as atouch -operated monostable andwired, as shown, across the LED dis-play switch: C and R may be selectedfor a shorter or longer time period,those specified will enable the displayfor about 15 minutes. The remainingtwo sections of the 4066 are used tocontrol the other functions, set time,etc., of the watch module.

Note that, in the stabiliser section,LED's are deliberately used to providethe reference voltage at the base of Tisince they 'zener' at appreciabilysmaller currents than a normal zenerdiode; total current of the stabiliserand clock (display off) is about 2 rrA

the smallest car battery should beable to supply this for about a year!

Jana kits are available from manydealers across Canada, includingthe following:

Canadian AdmiralQUEBEC CITYCesco ElectronicsMONTREAL

Cesco ElectronicsQUEBEC CITY

Cite Electronique Inc.MONTREAL

Cite Electronique Inc.QUEBEC CITY

Cite Electronique Inc.SHERBROOKE

Colonial Electronic Ltd.MONTREAL

Commercial RadioMONTREAL

Crobel Ltee.PARC JEAN TALON NORD

Distribution J.M.C. Inc.MONT-JOLI

Electronic Wholesalers (St. Jean) Ltee.ST. JEAN

ETCO ElectronicsPOINTE CLAIRE

Gemobel ElectronicCHICOUTIMI

Gemobel ElectronicSEPT ILES

La Salle DistributorsVILLE LA SALLE

Lemco DistributorsST. JEROME

LevelcoGRANBY

LevelcoST. HYACINTHE

Master Vox Ltd.LONGUEUIL

Matteau (Cite Electronique Inc.)MONTREAL EAST

Matteau ElectronicsTROIS RIVIERES

Matteau ElectronicsSHAWINIGAN

Metropolitain ElectroniqueMONTREAL NORTH

Montcalm ElectroniqueLAVAL

P.L. TremblayJONQUIERE

Payette RadioMONTREAL

SimtroniqueNORANDA

Transtronique Inc.ST. GEORGES DE BEAUCE

TreJeanAMOS

Vision Tronics Ltd.SHERBROOKE

Wackid RadioOTTAWA

For the names of other dealers orfor institutional enquiry, write:Mr. D. MannJana Industrial1777 Ellice AveWinnipeg Man R3H OW5

76

_JanaMality Kits

LJ 12016AProject # 23

Color OrganThe Jana Color Organ is an ideal project for the experimenter who is a musician or a serious audiophile. This

project is a three channel color organ with a capacity of 200 watts per channel." It comes complete with the PC boardand instructions and its high power capability makes it ideal for all kinds of lighting effects, either with spotlights orback -lit lucite panels.

Remember, Jana projects come complete with electronic components of the exact value, so there's no need tosubstitute or hunt for specific capacitors, transistors or IC's.

Pick up a Jana Color Organ kit at your nearest Jana dealer today and while you're there, check out the otherJana Quality Kits.

1. Automatic Headlight Reminder 10. Fish Caller 19. Tone Generator2. Battery Operated Fluorescent 11. Hi Power 12V DC Flasher 20. 5 Transistor 1 Watt Amplifier

Light Kit 12. Photo Electric Night Light 21 Tube Continuity Checker3. Bug Shoo 13. 6V Power Supply 22 Xenon Strobe4. Code Oscillator 14. 9V Power Supply 23 LJ 12016A Color Organ5. Crystal Radio 15. 0-24V Power Supply 24 Loudmouth Siren7. Curiosity Box II 16. Single Channel Color Organ 25 Roulette Wheel8. Daily Lighter 17. Electronic Siren 26 Electronic Skeet Game9. Decision Maker 18. Shimmer Strobe Light 27 Electronic Dice

28 Super Roulette*Optional circuit to increase wattage capability to 1,000 watts per channelis shown in the instructions. 29 FM Mini Broadcaster

Available from

CAM GARD SUPPLY LTD

"

Distributors of all Jana kits, plus parts and components for most Electronics Today projects. Come in or mail your order. Offices across Canada.VANCOUVER2055 Boundary Road604-291-1441

KAMLOOPS825 Notre Dame Drive604-372,-3338

SASKATOON1501 Ontario Avenue306-652-6424

CALGARY640 -42nd Avenue S.E.403-287-0520

HEAD OFFICE, WINNIPEG1777 Ellice Avenue204-786-8401

EDMONTON RED DEER16236-40, 116th Avenue 4910 -52nd Street403-454-5254 403-346-2088403-453-6691

FREDERICTON MONCTONRookwood Avenue 15 Mount Royal Blvd.506-455-8891 506-855-2200

REGINA1303 Scarth Street306-525-1317

HALIFAX, N.S.3065 Robie Street902-454-8581

The

FunofElect-ronicsI HEARD A FELLA ON THE RADIOTHE OTHER DAY SAY THAT WESHOULD ALL CONSIDER USING THESUN TO HEAT OUR HOMES. . .

BUT I DON'T THINK IT WOULD FITIN MY BASEMENT.

L.J

GE? 61i1;

I'M AFRAID, SIR, THAT THE ONLY AUDIO COMPRESSOR WE HAVE FORUNDER THIRTY DOLLARS IS BRUNO HERE.

DON'T LOOK UPON THIS AS A FAILURE INCIRCUIT DESIGN, JOE, LOOK AT IT AS THEDISCOVERY OF THE WORLD'S FIRST LIGHTEMITTING TRANSISTOR!

THIS MORNING MY WIFE ASKEDME WHAT I WAS BUILDING, I TOLDHER I WAS WORKING ON A MULTI -VIBRATOR CIRCUIT - SHE TH-OUGHT I WAS BEING KINKY.

Y'KNOW, I'VE GOT OVER $5000 WORTH OF CB, HAM, AND SHORT-WAVE EQUIPMENT HERE, AND I'M NOT REALLY THAT INTER-ESTED IN ELECTRONICS OR COMMUNICATIONS - IT'S JUST THATWITH A WIFE AND TWO DAUGHTERS, / DON'T STAND A CHANCEOF GETTING NEAR THE TELEPHONE.


Ott 6&A WtCt

7166hg.6 WotETI's new classified advertising section allows you to reach 30,000 readersnation-wide. For as little as $15 (there's a 20 word minimum) you can pro-mote your business from coast to coast.

WHAT DO YOU DO?Send us your typewritten or clearly printed words, your permanent add-ress and telephone number, and your money (no cash please). Make yourcheque or money order payable to 'ETI Magazine'. We're at Unit 6, 25Overlea Blvd., Toronto, Ontario M4H 1B1.

WHAT DO WE DO?We typeset your words (and put the first word and your company namein bold capital letters).If we get your message by the 14th of the month, it will appear in ETI11/2 months later. For example, if we receive it by November 14th, you(and thousands more) will see it in the January issue

SPECIAL! 1000 pieces for $10.00. Choke-capacitor-diode-hardware-insulator-rectifier-relay-resistor-transitor-speaker-switch-trans-former-zener-etc. Money back guarantee.Free flyer & sample on request. SURPLUSELECTRO-, Quebec, 2264 Montee GagnonBlainville, P.Q., J7E 4H5.

$1.00 Unusual Canadian and Americanparts and surplus catalogs. Hundreds ofbargains. ETCO, Dept 087, 183G Hymus,Pointe Claire, Que.

NEED sersatile power supple lor Jitterentkinds of projects? All you really need is this:Regulated Variable Power Supply Kits - (2to 35V 2.5 Amp), IC controlled.short, overload protected, 2N3055 output,easy to assemble, excellent design, everycomponent accessory. PCB included, lesstransformer. Just $18.00 EA or 2 for $33.00.B.C. orders add tax. LINEAR ELECTRIC,P.O. Box 80005, South Burnaby, B.C. V5H3X I.

CLASSIFIEDWSI SALES COMPANY - SWL Radios -Ham radios - 18 Sheldon Avenue North,Kitchener, Ontario N2H 3M2. Telephone(5191 579-0536. Write for giant catalog, freeof course!! (VE3EHC)

UNDERSTAND Digital Electronics.Programmed learning courses. Design ofdigital systems, 6 volumes, only $14.95.Digital computer logic, 4 volumes $9.95Both $19.95. Free details . GFN INDUST-RIES INC,. Bldg. 7-20, 203 Loudon Rd,Concord, NH 03301.

YOU need it? Chances are we sell it!Send us your parts list for free pricequotations. Don't forget, our lists andflyers come out regularly. Don't missout! BRYAN ELECTRONICS, P.O. Box2068, Bramalea, Ontario. L6T 3S3.

NEW STORE! for the Hobbyist, Ham,Audio, CB'r. Digital clock kit 12/24hr. with case $29.95. Ont: Res. add 7%sales tax. GENERAL ELECTRONICS5511 Yonge St., Willowdale, Ont. 221-6174.

AMPLIFIER Kits: 140W Class AB Stereo$129.00. 60- - 100W Class A Mono $58.00Stereo L.E.D. Audio Level Display:- 10steps $26.00. 18 steps $56.00. Free flyer:AUDIOVISION, Box 955, Stn B, Willow -dale. Ont. M2K 2T6.

J & J EI.ECTRONICS LTD., P.O. Box 1437E. Winnipeg. Manitoba R3C 2Z4. SurplusSemiconductor Specialists Do you getour bargain flyer? Send $1.00 to receivethe current literature and specials and tobe placed on the mailing list for futurepublications.

AP SUPERSTRIP SS -2 Solderless bread-boards. 61/2 by 21/4 inches. Immediatedelivery. $20.95 postpaid. WOLVERTONENTERPRISES, Dept ETI, 5 SouthHythe, Burnaby, BC, V5 B 3H6.

FREE CA3I40 with all orders of $5.00 ormore. SN76477N Complex Sound GeneratorIC. $2.95 or 2 $5.50. LM3I7T 1.5 AmpAdjustable Positive Voltage Regulator. $2.95or 2;$5.75. Include $1.00 for shipping -handling. Make all checks payable in U.S.Funds. Send for FREE catalog. KEYELECTRONICS, Box 3506E, Schenectady,NY 12303 U.S.A.

BE off to a good start with your projectsuse our P.C. Boards. ETI No, Price: No 812,$4.90 No 490, $4.60 No 592, $13.90 No 591C, $2.25 No 550, $3.55 No062, $3.00 No 243,$2.45 No 135,$4.00 No 593, $6.90 No 133, $5.10Write for full list to:-B&R ELECTRONICS,Box 6326F, Hamilton, Ontario,L9C 6L9.

NORTHERN BEAR ELECTRONICS Box7260, Saskatoon, SK S7K 4J2. June ETIKits; Colour Sequencer (parts & PCB)$45.00. (& power supply) $65.00. Dig-ital Temp. Meter (lettered case,PCB, allparts) $115.00. ICL7106EV $74.95. STACTimer IC $17.95. Add $1.00 P/H. Sask. addtax Free Flyer.


ETI Project FileUpdates, news, information, ETI gives you project support

PROJECT FILE is our department dealing withinformation regarding ETI Projects. Each monthwe will publish the Project Chart, any Project Noteswhich arise, general Project ConstructorsInformation, and some Reader's Letters andQuestions relating to projects.

PROJECT NOTESSince this magazine is largely put together by

humans, the occasional error manages to slip by usinto print. In addition variations in componentcharacteristics and availability occur, and manyreaders write to us about their experiences inbuilding our projects. This gives us informationwhich could be helpful to other readers. Suchinformation will be published in Project File underProject Notes. (Prior to May 78 it was to be found atthe end of News Digest.)

ISSUE ARTICLEDATE

Mar 78June 78Feb 79

Mar 78Apr 78Jan 79Feb 79

Mar 78Apr 78Apr 78Apr 78May 78June 78Apr 79

May 78June 78

May 78June 78

June 78June 78June 78July 78Aug 78

July 78Aug 78

July 78Aug 78

July 78Aug 78

Aug 78Dec 78

Aug 78Aug 78Aug 78Sept 78

Nov 78Sept 78

Nov 78

Hammer ThrowNeg.Note:C,DTrue RMS MeterNeg.Note:NNote:NHome Burglar AlarmComputer PSU & Neg.Audio Delay Line & Neg.Gas Alarm & Neg.White Line FollowerNeg.Note:CAcoustic Feedback EliminatorNeg.Add-on FM TunerNeg.Audio AnalyserUltrasonic Switch & Neg.Phone Bell Extender & Neg.Proximity SwitchNeg.Real Time Analyser MK II (LED)Neg.Acc. Beat Metronome.Neg.Race TrackNeg.Sound Meter & Neg.Note: NPorch Light & Neg.l8 Metal Locater & Neg.Two Chip Siren & Neg.Audio OscillatorNeg.Shutter TimerNeg.

Should you find that there are notes you wish toread for which you do not have the issue, you mayobtain them in one of two ways. You can buy theback issue from us (refer to Project Chart for datecfissue and see also Reader Service Information onordering). Alternatively you may obtain aphotocopy of the note free of charge, so long asyour request includes a self addressed stampedenvelope for us to mail it back to you. Requestswithout SASE will not be answered.

PROJECTCONSTRUCTOR'SINFORMATION

Useful information on the terminology andnotation will be published each month in ProjectFile.

ISSUEDATE

Sept 78Oct 78

Nov 78Oct 78

Nov 78Oct 78Apr 79

Nov 78Nov 78Nov 78Dec 78

Feb 79Mar 79

Dec 78Feb 79

Dec 78Feb 79

Jan 79Feb 79

Jan 79Feb 79

Jan 79Feb 79

Feb 79Feb 79Feb 79Mar 79Mar 79Mar 79Apr 79Apr 79Apr 79May 79May 79May 79

ARTICLE

Rain AlarmCCD PhaserNeg.UFO DetectorNeg.Strobe IdeaNote:NCap Meter &Neg.Stars & DotsCMOS Preamp & Neg.Digital AnemometerNegNote:C. D

Tape Noise ElimNegEPROM ProgrammerNeg

Log Exp Convert.NegDigital Tach.NegFM TransmitterNeg

Phasemeter & NegSW RadioLight Chaser & NegTape -Slide SynchSynth. Sequ.Dual DiceSolar ControlAudio CompressorWheel of FortuneLight ControllerAM TunerVHF Ant.

PROJECT CHARTThis chart is an index to all information available

relating to each project we have published in thepreceding year. It guides you to where you will findthe article itself, and keeps you informed on anynotes that come up on a particular project you areinterested in. It also gives you an idea of theimportance of the notes, in caseyou do not havetheissue refered to on hand.

Every few months we print a pull out section inthe magazine which may be used as aphotographic negative for making printed circuitboards (as described in our January 78 issue).Each edition of this sheet contains projects fromthe preceding few issues. Information on where tofind which negative is included in the chart.

Write to: Project FileElectronics Today InternationalUnit 6, 25 Overlea Blvd.,TORONTO, OntarioM4H 1B1

Component Notationsand UnitsWe normally specify components using aninternational standard. Many readers will beunfamiliar with this but it's simple, less likely to leadto error and will be widely used sooner or later. ETIhas opted for sooner!

ETI ProjectChart

Canadian Projects BookAudio Limiter5W StereoNotes N, D May 79

OverledBass EnhancerModular DiscoG P PreampBal. Mic. PreampCeramic Cartridae PreampMixer & PSUVU Meter CircuitHeadphone Amp50W -100W AmpNote N May 79

Metal LocatorHeart -Rate MonitorGSR MonitorPhaserFuzz BoxTouch OrganMastermindDouble DiceReaction TesterSound -Light FlashBurglar AlarmInjector -TracerDigital Voltmeter

Key to Project NotesC:- PCB or component layoutD:- Circuit diagramN:- Parts Numbers, SpecsNeg:- Negative of PCB pattern printed0:- OtherS:- Parts SupplyT:- TextU:- Update, Improvement, Mods" :- Notes for this project of complicatednature, write for details (enclose S.A.S.E., seetext)

I


ETI Project FileFirstly decimal points are dropped and

substituted with the multiplier, thus4.7uF is written4u7. Capacitors also use the multiplier nano (onenanofarad is 1000pF).Thus 0.1uF is 100n,5600pF is5n6. Other examples are 5.6pF = 5p6, 0.5pF = Op5.

Resistors are treated similarly: 1.8M ohms is1M8, 56k ohms is 56k, 4.7k ohms is410, 100ohmsis100R, 5.6 ohms is 5R6.

Kits, PCBs, and PartsWe do not supply parts for our projects, these

must be obtained from component suppliers.However, in order to make things easier we co-operate with various companies to enable them topromptly supply kits, printed circuit boards andunusual or hard -to -find parts. Prospective buildersshould consult the advertisements in ETI forsuppliers for current and past projects.

Any company interested in participating in thesupply of kits, pcbs or parts should write to us ontheir letterhead for complete information.

READER'S LETTERS ANDQUESTIONS

We obviously cannot troubleshoottheindividualreader's projects, by letter or in person, so if youhave a query we can only answer it to the extent ofclearing up ambiguities, and providing ProjectNotes where appropriate. If you desire a reply toyour letter it must be accompanied by a selfaddressed stamped envelope.

PLEASE NOTE: WE CANNOTANSWER PROJECT QUERIESBY TELEPHONE,

-Luse SEA/4 ,.VLOUR Aovxg-r'.zse,..skrr

use -IA) en19ry svf<E-E,EXIL,C,:koel,,,r,y yowl,I77tS546C roor .e4cr.

ETI MPAIKT ACE,ire, IS OVIlt OlVD,TORONTOM4 -I-1 1E51

CANADIAN PROJECTS BOOK

50/100 AMPLIFIERRepeating for those who missed itbefore: Q6 is incorrectly shown as a2N4250, it can be replaced by a

2N3904.

Some confusion has resulted over thedriver transistors in this project. Thetypes of transistors used in the proto-type were the BD139 (Q4, 08) andBD140 (Q5 and Q7), with alternatesTIP29C and TIP30C. Although elec-trically equivalent, these latter typescannot be mounted with either faceagainst the heatsink, as can the BDtypes. Naturally, it turns out that theface that can be mounted towards theheatsink (07, 08) results in the leadsbeing in the reverse order for the pcb.

Solution? Mount Q8 and Q9 asshown but use jumper wires to get the eand b connected to the right points,or cut neat holes in the pcb and mountthem on the back side (leads will nowbe in order), or redo the pcb. Apology?Heh heh sorry about that!

By the way, DON'T FORGET TOUSE INSULATORS FOR ALL HEAT -SINK MOUNTED TRANSISTORS!

untiTC Tot, gMES5A4E ,otter.

Chow, Fo4-r YOURmArne neorcssm/E.

READERS' FREE ADVERTISING

ITNow Available

ETI True RMS Voltmeter$89.95

ETI Bucket BrigadeAudio Delay Line $59.95ETI Frequency Shifter . . $69.95ETI Ultrasonic Switch . . $29.95ETI CCD Phaser $79.950-24V 1 Amp Power Supply

$19.953 Channel Colour Organ

500W SCR $19.951500W TR IAC $29.95

2W 12V Audio Amplifier$8 95

Strobe Light $14.95Light Chaser Kit (10 LEDs,Variable Speed) $19.95

Cheque, Money Order or MasterchargeInclude card expiry date and number

Ontario residents please add 7% sales tax

DO NOT SEND CASHAllow 3 weeks for delivery

DOMINION RADIO &ELECTRONICS

535 Yonge St. TorontoOntario M4Y 1Y5

MARKET PLACEI NEED THE INSTRUCTION MANUAL FOR TRANSISTORANALYSER MODEL 212 FROM E.M.C. A. BOISVERT4830 DES PERVENCHES, ORSAINVILLE, QUEBEC G1G 1R7

INTERESTED IN ELECTRONICS OR PHYSICS BUT DON'TKNOW A CLUE WHAT YOUR DOING? WRITE: A.P.O. W.S.(1SSB), 716 SABRINA RD. S.W., CALGARY, ALBERTA,T2W OP3 FOR FREE CATALOG ON ELECTRONICS ANDPHYSICS, CLUBS, ETC.

FOR SALE: 150 WATTS WATSON LABORATORIESSTEREO SPEAKERS. CONSIDERED TO BE THE WORLD'SBEST. IN ORIGINAL CARTON. CALL (416) 630-8343 ORBOX 1358, STATION B, DOWNSVIEW, ONT. M3H 5W3.FOR SALE: B&K 415 SWEEP MARKER GEN., B&K 1470OSCILLOSCOPE $450, B&K 1801 COUNTER $250, B&KTRANS. TEST. $50, HEATHKIT 1M30 TRANS. TESTER$50, AN URM FREQUENCY METER GENERATOR $150,HICKOK MODEL 770 OSCILLOSCOPE $200, COLLINS30AR R41-502 RECEIVER $210, ALL WITH SPEKS.FRANZ MASCHMANN RR 1, DWIGHT, ONT. POA 1H0.WANTED: SCHEMATIC, ALIGNMENT DATA, AND OWN-ERS MANUAL, FOR HALLICRAFTERS SX-62 A -GENERALCOVERAGE RECEIVER. J.A. SHAW 16 ROBINSON LANEPEMBROKE, ONT. K8A 7S1 (613) 735-1911.FOR SALE: CLASSIC TUBE EQUIPMENT: 2 MCINTOSHMC 75 MONO AMPS; 75 WATTS EACH - BEST OFFEROVER $700 FOR BOTH. ALSO CITATION I, II, III (PRE-,60 WPC POWER -AMP & TUNER) BY HARMAN-KARDON.BEST OFFER OVER $600. (416) 531-6590. BOX 157 STN.VTORONTO, ONT. M6R 3AR.POLLY 88 KEYBOARD,COMPUTER FOR SALE: 32K RAM12" CRT. 2400 BAUD CASSETTE R 523JPRINTER PORT. BASIC AND ASSEMBLER. TONS OFSOFTWARE. $1795. CALL A. HABER OR WRITE BON 190LA PRAIRIE, QUE. J5 R 3Y2.

FOR SALE: FULLY ASSEMBLED AND TESTED ELF1 I

COMPUTER WITH STEEL CABINET, 4 AMP POWER SUPPLY4K RAM, '/4K SYSTEMS MONITOR/EDITOR, VIDEO OUT-PUT, RF MODULATOR, CASSETTE 1/0, ASC II KEYBOARD,LIGHT PEN, 2 PARALLEL I/O PORTS, RS232/20MA TTYI/O, HEX KEYBOARD AND DISPLAY, SPEAKER, PROTO-TYPE BOARD, ELFBUG MONITOR, TINY BASIC AND OVER2000 PAGES OF DOCUMENTATION. A SWITCH CHANGESTHE SYSTEM INTO A COSMAC VIP WHICH ALLOWS SO-PHISTICATED CHIP -8 PROGRAMS TO BE RUN. ASKING$400. MARK RUDMIT, 139 MACDONNELL ST., KINGSTONONT. K7L 4B9, (613) 549-6067.WANTED: SCHEMATIC FOR HALICRAFTER RECEIVERMODEL TW2000. EDOUARD DION, 3160 RIVIERE CACHEEBOISBRIAND, QUE. J7H 1A3.

REQUIRED: SHOP MANUAL AND/OR SOURCE OF PARTSFOR EOHOLELLE TYPE NG51 ECHO UNIT. PAULBISSONNETTE, BOX 1977, INNISFAIL, ALBERTA TOM 1A0(403) 227-3916.

FOR SALE: REVOX 8790, SAE 2.900, QUAD405 LUXMANT33, RG1, AUDIO TECHNICA AT 706, ALTCE 5, 30% OFRETAIL PARTIAL OFFER ACCEPTED. GILBERTGUIMOND, 5847 MIGNAULT, MONTREAL, QUE. H1M 1Y9(514) 254-5696.

TINY -C & ASSEMBLER PROGRAMMING BULLETIN FORTRS-80. $1 BRINGS YOU ISSUE PLUS BASIC. ASM ANDSYSTEM TAPE FORMATS. R. VARTY, 2193 HAYGATE CR.MISSISSAUGA, ONT. L5K IL7.

WANTED: SCHEMATIC FOR WEBCOR WFX239 AM/FM8 TR STEREO. ROBERT MCNEIL, 6 ALLEN'S ROAD COR-NER BROOK, NFLD. A2H 3T7.FOR SALE: H.P. 200CD OSCILLATOR 5HZ TO 600KHZ.MORRIE ALTMEJD P.O. BOX 368, DOWNSVIEW, ONT.M3M 3A8, (416) 928-9139. PRICE: $200.


ReaderServiceInformation

Editorial QueriesWritten queries can only be answeredwhen accompanied by a self-addressed,stamped enveloped, and the reply cantake up to three weeks. These mustrelate to recent articles and not involveETI staff in any research. Mark yourletter ETI Query.

Projects, Components,NotationFor information on these subjectsplease see our Project File section.

Sell ETIETI is available for resale bycomponent stores. We can offer a gooddiscount and quite a big bonus, thechances are customers buying themagazine will come back to you to buytheir components. Readers havingtrouble getting their copy of ETI couldsuggest to their component storemanager that he should stock themagazine.

Back Issues andPhotocopiesPrevious issues of ETI-Canada areavailable direct from our office for$2.00 each. Please specify issue by themonth, not by the features you require.The following back issues are stillavailable for sale.

1977 1978 1979February milageriiiim JanuaryMay February FebruaryJune March MarchJuly April AprilSeptember May MayNovember June June

JulyAugustSeptemberOctoberNovemberDecember

We can supply photocopies of anyarticle published in ETI-Canada, forwhich the charge is $1.00 per article,regardless of length. Please specifyissue and article. (A special con-sideration applies to errata forprojects, see Project File.)

LIABILITY: Whilst every effort has been made to ensure that all constructional projects referred to in this edition will operate as indicated efficiently and properly and that all necessarycomponents to manufacture the same will be available, no responsibility whatsoever is accepted in respect of the failure for any reason at all of theproject to operate effectively or at allwhether due to any fault in design or otherwise and no responsibility is accepted for the failure to obtain any component parts in respect of any such project. Further no responsibility isaccepted in respect of any injury or damage caused by any fault in the design of any such project as aforesaid.

- - -

The new video cassette recorders are a bit smaller thanthose available in 1870, in fact they are quite compact..It also seems that the "standards" battle is about over,with only two systems left. SO, now manufacturers canget down to serious business, and buyers can be confi-dent that the machine they purchase is not going to bean orphan. Next month we survey the available mach-ines, Steve Rimmer tells the story. Plus: A sophisticatedtimer (based on the STAC), and a light activated tachoproject. And of course much more. Stay tuned!

Advertisers' Index

Allan Crawford AssociatesAlpha Tuner ServiceCastle Tuner ServiceCeres

Classifieds

6

58

72

7279

Compumart 49, 50Computer Specialists 36Dominion Radio and Electronics 81

Heathkit 30House of Computers 36Jana 76, 77Len Finkler 10, 12, 16Marketron 41Metermaster 10McGraw Hill 19RCA Solid State 84Webster Instruments 83Zenith Radio 70


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Color. VP -590 add-on Color Board allows programcontrol of 8 brilliant colorsforgraphics, color games.Plus 4 selectable background colors. Includessockets for 2 auxiliary keypads (VP -580). $69!

Sound. VP -595 Simple Sound Board provides 256tone frequencies. Great for supplementing graphicswith sound effects or music. Set tone and durationwith easy instructions. $247

Music. VP -550 Super Sound Board turns your VIP into a musicsynthesizer. 2 sound channels. Program control of frequency,time and amplitude envelope (voice) independently in eachchannel. Program directly from sheet music! Sync provisionfor controlling multiple VIPs, multitrack recording or othersynthesizers. $49'

Memory. VP -570 RAM Expansion Board adds 4Kbytes of memory. Jumper locates RAM in any 4Kblock of up to 32K of memory. On -board memoryprotect switch. $95"

EPROM Programmer. VP -565 EPROM Programmer Boardcomes complete with software to program, copy andverify 5 -volt 2716 EPROMs-comparable to unitscosting much more than the VP -565 and VIP puttogether! Programming voltages generated onboard. ZIF PROM socket included. $99!

EPROM Interface. VP -560 EPROM InterfaceBoard locates two 5 -volt 2716 EPROMs (4Kbytes total) anywhere in 32K of memory.VIP RAM can be re -allocated. $34!

ASCII Keyboard** Fully encoded, 128 -character ASCIIencoded alpha -numeric keyboard. 58 light touch keysincluding 2 user defined keys! Selectable upperand lowercase. Handsomely styled. Under $50!

Tiny BASIC,* VP -700Expanded Tiny BASIC Boardputs this high-level languageon your VIP. BASIC storedin 4K of ROM. Ready for im-mediate use-no loadingnecessary. This expandedBASIC includes the standardTiny BASIC commands plus12 additional-includingcolor and sound control!Requires external ASCIIencoded alpha -numerickeyboard. $39'

Auxiliary Keypads. Programyour VIP for 2 -player inter-action games! 16 -key keypadVP -580 with cable ($15')connects to sockets pro-vided on VP -590 Color Boardor VP 585 Keyboard InterfaceCard ($10').

COSMAC VIP lets you addcomputer power a board at a time.

With these new easy -to-buy options, the versatileRCA COSMAC VIP(CDP18S711) means evenmore excitement. Morechallenges in graphics,games and control func-tions. For everyone, fromyoungster to serious hobby-ist. And the basic VIP com-puter system starts at just $249* assembledand ready to operate.

Simple but powerful-not just a toy.Built around an RCA COSMAC micro-

processor, the VIP includes 2K of RAM. ROMmonitor. Audio tone with a built-in speaker.Plus 8 -bit input and 8 -bit output port to inter-face relays, sensors or other peripherals. It's

easy to program and operate.Powerful CHIP -8 interpre-tive language gets you into'programming the firstevening. Complete docu-mentation provided.

Take the first step now.Check your local corn-

puter store or electronics0\ parts house. Or contactRCA Ltd... VIP Sales, 1 Vulcan St., Rexdale,Ontario M9W1L3. Phone (416) 247-5491.'Suggested retail vices in U.S. dollars. CDP18S711 does not include video monitor orcassette recorder"Available 1st Quarter. 1979

The fun wayinto computers. RCA

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