telephone call recording and answering machine system

8/8/2019 Telephone Call Recording and Answering Machine System

1/33

CONTENTS

1. Introduction

2. Block Diagram

3. Block Diagram Working4. Component Used

5. Layout

6. Circuit Diagram

7. Circuit Diagram Description

8. Application

9. Advantages/ Disadvantages

10. Future enhancement

11. Conclusion

12. Appendices1 | P a g e D e p a r t m e n t O f E l e c t r o n i c s a n dI n s t r u m e n t a t i o n E n g i n e e r i n g


2/33

13. Bibliography

INTRODUCTION

Basic concept-

An answering machine ormessage machine, also

known as an answer phone (especially in the UK and some

Commonwealth countries), and sometimes/formerly known as an

ansaphone, ansafone or telephone answering device (TAD), is a

device invented in 1935, by Benjamin Thornton, and independently in

Switzerland by Willy Mueller. The simple recording and answering

machine, which in the absence of the Subscriber/owner of the telephone

instrument, respond to he incoming calls and also record themautomatically.

The telephone recording/answering machine is very

useful for subscribers and callers. The caller can record his message in

the machine and subscriber can hear all the incoming calls.

The telephone recording and answering machine is

consisting of following basic parts.

1. Ring detection

2. Inverter

3. Timer

4. Relay2 | P a g e D e p a r t m e n t O f E l e c t r o n i c s a n dI n s t r u m e n t a t i o n E n g i n e e r i n g
http://wiki/United_Kingdomhttp://wiki/Commonwealth_countrieshttp://wiki/Commonwealth_countrieshttp://wiki/United_Kingdom


3/33

5. Player and recording system

1. Ring detection- Ring detection unit consists of mono stable multi

vibrator and the decade counter. It detects the incoming ring from thetelephone line and counts the incoming rings.

2. Inverter- The output from the decade counter is come at pin 3 and,

which goes high at the beginning if the third ring. Then it inverted

and triggered the timer.

3. Timer- It is in mono stable mode. The inverter triggers it and this

i=output is fed to the led and relays.

4. Relays- There are there relays in the telephone recording/answering

machine. These are of 12v DC and 150 ohms. The timer IC energizes

the relay1. Then the dc supply is on for player.

5. Player and recording system- The player and recording system is

used to record the incoming calls and play these recording calls. For this

the dc supply is used for the player and the ac supply for recorder. In

this the player is on when any incoming calls is come then it is on and

start to play and indicate to caller that you will start your message and

then the recording is on and the call is recorded.

3 | P a g e D e p a r t m e n t O f E l e c t r o n i c s a n dI n s t r u m e n t a t i o n E n g i n e e r i n g


4/33

BLOCK DIAGRAM



5/33


6/33

Its block diagram shown in fig1. The incoming telephone line pair is

terminated into the ring detection unit comprising a constable flip-flop

followed by a ring counter to detect the incoming calls. After counting a

predetermined no. of rings, it triggers a timer (another mono stable flip-

flop) via an inverter. The output of timer is used for energisation of a set

of relays, which initiate the following action-

Switch on ac power to the tape recorder.

Switch on dc voltage to the tape player.

Reset the ring counter in the ring counter in the ring

detection section to make it ready for the next incoming call/ring.

However any fresh call/ring will be ignored as long as timer output stays

high. The timer output also controls the on time of the recorder and

player. The on time can be set as per length of the message to be

recorded/ played; say, two to three minutes. Simulate off hook state ofthe telephone, which is initially in on hook condition.

COMPONENT USED



7/33

List of components



8/33


S.NO

.

COMPONENT TYPE

1. Semiconductor

IC1, IC4 NE555 timer

IC2 CD4017

decade counter

IC3 CD40106

invertors

IC5 CD7812

regulator +12v

T1, T2 BE 547 n p n

Transistor

D1-D7 IN4007

rectifier diode

LED1-LED2 Red LED

2. Resistors

R1 100-kilo ohm

R2,R7 4.7-kilo ohm

R3,R4,R8 10-kilo ohm

R5 33-kilo ohm

R6 2.2ohm

R9,R10 1 kilo ohm

R11 470 ohm

VR1,VR2 1-mega-ohm,

1 kilo ohm

preset

3. Capacitor

C1,c2,c4,c5 .1 uf, 25v

ceramic disk

C3 10uf, 25v


9/33

Theory

RESISTOR-

A resistor is a two terminal electronic component

designed to oppose an electric current by producing a voltage drop

between its terminals in proportion to the current, that is, in

accordance with Ohms law:

V=IR



10/33

Resistors are used as part of electrical networks &

electronics circuits. They are extremely common place in most

electronic component . Practical resistors can be made of various

compounds & films, as well as resistance.

The primary characteristics of resistors are their

resistance and the power they can dissipate. Other characteristics

include temperature coefficient, noise & inductance.

CAPACITOR

A capacitor or condenser is a passive electronic

component consisting of a pair of conductors separated by a

dielectric. When a voltage potential difference exists between the

conductors, an electric field is present in the dielectric. This field



11/33

stores energy and produces a mechanical force between the plates.

An ideal capacitor is wholly characterized by a constant capacitance

C, defined as the ratio of charge Q on each conductor to the voltage V

between them:

C=Q/V

The properties of capacitor in the circuit may

determine the resonant frequency and quality factor of a resonant

circuit, power dissipation and operating frequency in a digital logic

circuit, energy capacity in a high power system, and many other

important system characteristics.

RECTIFIER-

The rectifier is used to convert the AC signal into DC11 | P a g e D e p a r t m e n t O f E l e c t r o n i c s a n d

I n s t r u m e n t a t i o n E n g i n e e r i n g


12/33

signal. The DC supply is used in many electronic ckt. In this ckt the

rectifier is also used for supplying this voltage to the relays.

The rectifier has two types.

1. Half wave rectifier

2. Full wave rectifier

1. Half wave rectifier- In this the rectifier conducts current only

during the positive half-cycles of input ac supply. The negative half

cycles of ac supply are suppressed i.e. during negative half cycles.

2. Full wave rectifier- In this full wave rectifier, current flows

through the load in the same direction for both half cycle of input

ac voltage. This can be achieved with two diodes working

alternately.

It is of two types-

1. Centre-tap full wave rectifier

2. Full wave bridge rectifier



13/33

1. Centre-tap full wave rectifier- In the telephone

recording/answering machine we used the centre tap rectifier. The

ckt employs two diode D1 & D2 as shown in fig. A centre tapped

wave is used with two diodes connected so that each used one half-

cycles of input ac voltage.

OPERATION-

During the positive half-cycles of secondary voltage,

the end A of secondary wdg becomes positive and end B negative. This

makes the diode D1 forward biased and diode D2 reverse biased.

Therefore diode D1 conducts while D2 does not. The conventional

current flows is through diode D1, load resistor RL and the upper half of

secondary wdg becomes negative and B positive. Therefore D2 conducts

while D1 does not. The conventional current flows through D2,RL and

lower wdg. So both positive and negative cycles at input is becomes

positive.

T

RANSISTOR-13 | P a g e D e p a r t m e n t O f E l e c t r o n i c s a n d



14/33

A transistor consist of two pn junction formed by

sandwiching either p type or n type semiconductor between a pair of

opposite type

N-P-N Transistor

P-N-P Transistor

A transistor has three section of doped semiconductor.

(a)Emitter: - the section on one side that supplies charge carriers is

called the emitter. The emitter is always forward biased with

respect to base.

(b)Collector: - the section on the other side that collects the charge is

called the collector biased. The collector is always reversed biased.

(c)Base: - The middle section which form two pn junction between

The emitter and collects is called the base. The base emitter

junction is forward biasing allowing low resistance for the emitter ckt.

The base collector junction is reverse biased and provides high

resistance in the collector ckt.



15/33

OPERATION-

In the circuit there is used of two NPN transistor.

The first transistor is used for triggered the 555 IC. The signal is come

from the telephone lines and then the collector voltage is low of the

collector for just milli second and that time the 555 is triggered by is

connected to the output of the second 555 IC. This transistor is used for

the amplification of current to remove the loading effect of circuit.

555 TIMER

Pin Decription

555

1

2

8

7

6

5

4

3

Ground

Trigger

Output

Reset Control voltage

Threshold

Discharge

+Vcc



16/33

PIN 1- Ground: All voltage are measured with respect to this terminal.

PIN 2- trigger: the output of the timer depends on the amplitude of the

external.

PIN 3- Output: there are two ways a load can be connected to the

output terminal either between pin3 and ground pin1 or between pin3

and supply voltage +Vcc. When the output is low, the load current

flows through the load connected between pin3 and +Vcc into the

output terminal and are called the sink current.

PIN 4- Reset: Applying a negative pulse to the can reset the 555 timers.

When the reset function is not in use, the reset terminal should be to

+Vcc to avoid any possibility of false triggering.

PIN 5- Control voltage: An external voltage applied to this terminal

change the threshold as well as the trigger voltage.

PIN 6- Threshold: This is the non inverting-input terminal of

comparator 1, which monitors the voltage across the external capacitor.

PIN 7- Discharge: It is used for discharge the capacitor.

PIN 8- Vcc: The supply voltage of +5 to +18v is applied.

MONOSTABLE OPERATION:

In the ckt there is two 555-monostable multivibrator

. The first is used for comprising the ring, which is come from the



17/33


18/33

is consisting of three terminals positive voltage regulators with seven

voltage options. The 7812 is designes as fixed voltage regulator and

with adequate heat sinking can deliver output currents in excess of

1A. although these devices do not require external components, such

components can be used to obtain adjustable voltage and currents.

This IC has internal short ckt current limiting. The fig shows, proper

operation requires a common ground between input and output

voltage (Vin-VO), called dropout voltage must be typically 2V.

IC4017

It is five stage Johnson counters having 10 decoded outputs

that are Q0 to Q9. In this circuit we had taken output from Q3 which is

on the 7 no. pin. Inputs include a clock a reset and a clock inhibit signal.

Schmitt trigger action in the clock input circuit provides pulse shaping

that allow unlimited clock input pulse rise and fall times.

This counter is advanced 1 count at the positive CLOCK

signal transition if the CLOCK INHIBITED when the CLOCK INHIBIT

signal is high. A high reset signal clears the counter to if zero count.



19/33

FEATURES

Fully static operation

Medium speed operation 10 Mhz at Vdd 10v

Standardization, symmetrical output characteristics

100% tested for quiescent current at 20v

5v, 10v and 15v parameter rating

APPLICATIONS:

Decade counter/decoder

Binary counter/decoder

Counter control/timers

Divide by-N counting.

For further application information see ICAN-6166COS/MOS

MSI Counter and register Design and application.



20/33

CD4017

Functional Diagram

Carry out

CLOCK 14

CLOCK INHIBIT 13

RESET 15

12

2 1

6 7

4 2

5 6

1 5

7 3

10 4

9 8

11 9

3 0



21/33

LAYOUT



22/33

CIRCUIT DIAGRAM



23/33

CIRCUIT DIAGRAM DESCRIPTION

23 | P a g e D e p a r t m e n t O f E l e c t r o n i c s a n d



24/33

The schematic diagram incorporating the control

circuitry, including power supply and relays, is shown in fig.2. the line

diagram, including all accessories used in the system, is shown in fig.3.

Normally, the telephone lines(in on hook position of the

hand-set) carry 50vdc. However, during ringing, the lines carry 133hz

80v ac (modulated pulses), as shown in fig.5.

Ring detection circuit comprises an input sensing

section followed by MMV and decade counter. In the input sensing

section capacitor c1 is used for dc blocking while IN4007 diode D1 is

used to rectify the ac ringing voltage. The potentiometer formed by

resistor R2& R3 (shunted by base-to-emitter resistance of transistor T1)

act as voltage/current limiting network for transistor T1. During the

positive incursions of the ringing voltage at the base of transistor T1, it

is driven into saturations. As a result, the collector of transistor T1 is

pulled LOW. This low going pulse is coupled to trigger pin2 of timer

NE555(IC1) configured as mono stable (re-trigger able). The output

pulse width is given by the relationship.

Pulse width=1.1R4*C3..seconds

Where R4 is in ohms and C3in Faradays.24 | P a g e D e p a r t m e n t O f E l e c t r o n i c s a n d



25/33

With the component values shown, the pulse width will

be roughly .36seconds. This will ensure that the mono pulse does no

t end during the pause period (.2 sec.) between two successive rings, so

that only one pulse is generated at the output of IC1 for each pair of ring

signals separated by .2 seconds.

The output of IC1 is coupled to clock input pin; 14 of;

the decade counter IC 4017 (IC2), which is used for counting the rings.

From the decade counter one can select any output from Q0 through

Q9. But in; this project we take the output from Q3, which goes high at

the beginning of the third ring so we can hear only two ring properly.

The Q3 output at pin 7 of IC2 is inverted by N1

inverter gate of IC3 to trigger timer IC4 (configured as mono stable),

Whos pulse width can be adjusted with the help of preset VR1. The

pulse width can be adjusted that the tape player could reply the required

message and the recorder could record the response from the far-end

subscriber within the set pulse width period. As stated earlier, timer IC4,

when triggered, initiates four different functions. These accomplished

via relay RL1-RL3 as follows:25 | P a g e D e p a r t m e n t O f E l e c t r o n i c s a n d



26/33

The output of timer IC4 energizes relay RL1. On

energisation, contact RL1 (a) of this relay extends +12v to the coil of

RL2 & RL3, thereby energizing both of them (RL2 & RL3). RL1 (b)

contacts of relay RL1 (on energisation) switch on the DC supplies to the

record player, whose play button is supposed to be already depressed.

(Please note that DC power supply for the player is not catered to in the

circuit. The supply voltage will depend on the make of the player, and

may very from one player to the other. In many cases, battery supply

(provided inside the player itself) could be routed via RL2 (a) contacts.)

Thus, it will start playing the pre recoded message, which would also be

in the released state, simultaneously via relay RL3 contacts, as

described later

RL2 (a) contacts of relay RL2, on energisation extend

+12v to reset pin 15 of counter IC2. Thus the counter remains reset until

IC4 timers output goes low again. RL2 (b) contacts of relay RL2, on

energisation, switch on 230v AC supplies to the tape recorder and thus it

can record the message received in the earpiece of telephone.

Relay RL3 performs the function cradle switch for the26 | P a g e D e p a r t m e n t O f E l e c t r o n i c s a n d



27/33

telephone in; the absence of the subscriber (or even during his presence,

if he fails to lift his handset off the cradle during ringing). Its contacts

RL3 (a) and RL3 (b) are wired in parallel with the hook switch.

.



28/33

APPLICATION

1. In the home we use this important when owner is not present.

2. It can be used in the security field.

3. It can be used in the medical field.

4. It can be used in the industrial fields.

5. It can be used in the crime branch.



29/33

ADVANTAGES/DISADVANTAGES

ADVANTAGES-

1. By this when any important call is coming that can be recorded in

the absence of the subscriber.

2. It can be used in anywhere with telephone instrument.

3. It is very simple instrument

4. Low cost.

DISADVANTAGES-

1. Any blank call is recorded.



30/33

2. It is dependent on the ac supply, when the light is not coming then

it will not work.

CONCLUSION

Working on the project on academic level, we found

a great difference in our theoretical background and practical doing,

choosing a simple resistor demanded a through knowledge backed by a

real time experience. Every step in our project stood as a testing our

patience and enhanced our level of confidence and developed the

appreciation for each results.

On personal level we inculterred in ourselves

magnitude of great values viz, team spirit, co-ordination and

combination, managerial abilities, preservence, communication skill

and decision-making. There a value has become our asset now. We also



31/33

learn that the proper planning is the key to success and by consistent

efforts, we can achieve anything in real life.

APPENDICES

YAHA PAR SARI DATA SHEETS LAGANA FIR USKE BAD BIBLIOGRAPHY WALA

PAGE LAGANA



32/33

BIBLIOGRAPHY

1. www.google.com

2. www.howstuffwork.com

3. www.efymag.com

4. www.datasheets4u.com

5. www.wikepedia.org



33/33

telephone call recording and answering machine system

Documents