msan 154 appnote jan05

8/7/2019 MSAN 154 AppNote Jan05

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Zarlink Semiconductor Inc.Zarlink, ZL and the Zarlink Semiconductor logo are trademarks of Zarlink Semiconductor Inc.

Copyright 2003-2005, Zarlink Semiconductor Inc. All Rights Reserved.

Contents

1.0 Introduction

2.0 What are the requirements for a D.A.A?2.1 Functional Block Description

2.1.1 DC Loop Termination

2.1.2 Line Impedance Matching

2.1.3 2-4 Wire Conversion

2.1.4 Supervisory Features

2.1.5 Protection

2.1.6 Line Isolation and Regulatory Require-

ments

2.1.7 RFI/EMC and Power Supply Design

Considerations

3.0 Zarlink Semiconductor DAAs

4.0 MH88422 Data Access Arrangement4.1 General Considerations

4.2 Applications Example

4.2.1 Gain Adjustment

4.2.2 Ringing detection

5.0 MH88435& MH88437 Data Access Arrange-

ments

5.1 Device Set up and Programming

5.1.1 DC Mask Programming

5.1.2 Network Balance Impedance

5.1.3 Detection of Line Reversals


5.1.5 The Loop Pin

6.0 MH88437 Data Access Arrangements

6.1 Device Differences

6.2 Device set up and programming

7.0 Using the MH88437 DAA with CTR21

7.1 Points of Note when Designing for CTR21

1.0 Introduction

The purpose of this application note is to provide

information on the operation and application of Zarlink

Semiconductors range of Data Access Arrangement

(DAA) devices.

DAAs can be used in a wide range of analog data and

voice transmission equipment, such as modems, Fax

machines, Electronic Point of Sale terminals and Set

Top Boxes. Figure 1 gives an example of a typical

modem system.

Zarlink Semiconductor DAAs can be used to provide a

complete interface between analog transmission

equipment and a telephone line. All functions areintegrated into a single module, providing high voltage

isolation, very high reliability and optimum circuit

design needing few external components.

The design requirements of the DAA have, over time,

become more stringent as data rates have increased

and markets have become global. Zarlink

Semiconductors range of components has been

developed to embrace the new requirements and are

being used by customers all over the world. This

application note will assist in using the Zarlink DAAs

with any grounded modem or other analog

transmission systems.

NOTE: Set top box is the name given to the decoder

units used with Cable and Satellite systems and

normally located with the TV sets.

January 2005

MSAN-154

Zarlink Data Access ArrangementDevices

Application Note

Figure 1 - Typical Modem System

ModemControl &

Data Pump

DATA SOURCE

Telephone

Line

LoopControl/

Supervision

DataAccess

Arrangement

System Equipment
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MSAN-154 Application Note

2Zarlink Semiconductor Inc.

Figure 2 - DAA Block Diagram

2.0 What are the requirements for a D.A.A?

2.1 Functional Block Description

The DAA has to perform a number of distinct functions in order to provide the level of functionality needed in

terminal equipment. Many of these functions have regulatory standards applied to them. Zarlink DAAs simplify

designs and provide a faster route to gaining regulatory approvals.

Figure 2 shows a schematic with the key features required of a DAA.

2.1.1 DC Loop Termination

The DAA is required to terminate the telephone line in the appropriate way dependent upon the status of the call. In

the on-hook state a high impedance must be applied to the line, i.e., no DC current flows in the loop. Each DAA

presents a high impedance to ground which is product related. (Refer to relevant product data).

An incoming call is detected by the presence of ringing, indicated on the ring detection pin. To answer the call a DC

termination is applied to the line by activation of the loop control pin, signalling to the exchange that a subscriber

has gone off-hook and is ready to set up the equipment initialization.

Where the call is initiated by the subscriber the DC termination is applied to the line, causing loop current to flow,

signalling to the exchange the initiation of the call.

Dialling can be performed either by using Dual Tone Multi Frequency (DTMF) signalling or by dial pulsing.

For the latter, the loop control pin can be used to interrupt loop current for pulse dialling.

Most countries have different DC mask requirements that need to be met. The term DC Mask relates to the current

vs voltage characteristics of the off-hook terminal equipment. These are set on the country variants of the MH88422

but can be changed on the MH88435/MH88437 with external components. The DC characteristics and

programming component values can be found in both data sheets.

Active

Termination

Barrier (Isolation)

2-4 Wire

Conversion

Impedance

Matching

Loop Monitor

and

Supervision

TIP

RING

VX

VR

Ringing Detect

Loop Current

DetectLoop Control

P

S

T

N

User

System

Data

Source


3/17



At the end of a call the DC load is removed by the DAA and the termination returns to a high impedance state.

2.1.2 Line Impedance Matching

To obtain optimum performance on a transmission link it is necessary to match the AC characteristics of the DAA to

those of the line. The characteristics of the line can vary according to the regulatory standards of a given country or

network operator.Two impedances are usually stated, these are the line characteristic impedance and the network balance

impedance.

The line impedance of the DAA must be matched by the termination impedance. A mismatch will cause losses and

echoes on the link, potentially increasing error rate, reducing transmission speed and even the interruption of

transmission. The line impedance can be resistive or complex.

The network balance impedance is chosen to ensure that data transmitted by the subscriber is not reflected back

into the DAA. This can be equal to the line impedance or a different impedance according to regulatory or operating

requirements.

For DAAs which must be used in international applications there must be a method of programming these

parameters. This method varies, dependent on the DAA used. Compromise values can be attached to the DAA,

for multi-country approvals and are available.

2.1.3 2-4 Wire Conversion

The DAA interfaces to a 2 wire telephone line which is a full duplex link. The DAA must extract from the line a

Transmit signal and place onto the line a Receive signal. This has to be done to enable the connection to other

devices such as Modem chipsets and DSP circuits which use a 4 wire connection.

Note: All Zarlink Semiconductor Analog Line Interface product information refers to "Transmit" as the 4W output

from a 2-4 wire converter and to "Receive" as the 4W input to a 2-4 wire converter.

Historically this function has been performed by a hybrid transformer, which provides good isolation but is bulky and

difficult to manufacture. Modern designs use active components to achieve this function, providing low cost and

high performance in a very small package.

Central to the design of a 2 to 4 wire converter is the need to cancel the transmitted signal on the telephone line. If

there were no cancellations, this signal appears at the input of the DAA and could be interpreted by the DAA as a

signal from the far end of the link. The measure of the ability of the DAA to cancel this signal is known as Trans

Hybrid Loss (THL).

Good THL is achieved by accurate matching of the Network balance impedance to the line impedances and is

usually stated for a given impedance and band of frequencies, as line length and discontinuities in the line will affect

performance. For operation with a variety of line lengths a compromise impedance can be used to give an

adequate THL, this removes the need to switch the balance impedance e.g., AT&T compromise.

2.1.4 Supervisory Features

The DAA must be capable of monitoring and controlling the line conditions for efficient management of the link. The

key control feature which is needed is the loop switch function. This is used to apply the correct termination to the

line and to provide pulse dialling facilities.

Line monitoring is needed to complete the signalling link from the far end. The signals which must be detected are

ringing, line reversals and the presence of devices connected to the line e.g. a telephone set in parallel with the

DAA. The nature of supervisory signals varies according to the service providers specification. External circuitry

may be required to detect line reversals and/or parallel phones. Not all functions are provided on all DAAs.


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Responses to changes in the line signalling conditions are generated by the controlling system processor, which

implements the appropriate protocols either through the DAAs line control facilities or the use of modem command

sets.

2.1.5 Protection

The use of active components in the DAA means that adequate protection from high voltages must beprovided. The high voltages can result from lightning strikes or fault conditions e.g., mains cables shorting to the

telephone line.

Specifications for protection are often particular to the PTT or service provider, but international standards do exist

such as ITU-T K.20.

Protection can be provided by components such as Fold Back diodes, Positive Temperature Coefficient Resistors

(PTCs), Transorbs and fuses.

It is not possible to show protection circuits to meet all requirements in this document, and due to the dynamic

nature of regulatory standards Zarlink Semiconductor recommends that users of Zarlink DAAs consult with

regulatory standards, standards bodies and approved test laboratories. However, an example is shown below of

circuits to meet specific needs (see Figure 3).

Figure 3 - Protection Circuit

Figure 4 - DAA and RFI Filters

2.1.6 Line Isolation and Regulatory Requirements

The DAA must provide isolation between the telephone line and the subscribers equipment. The isolation barrier

can be at various positions in the equipment, for example, in the power supply, in the DAA or a combination of

these. The precise method depends upon the type of equipment being built and the country in which it will operate.

TIP

RING

TR600-165Resettable

Fuses

Foldback

Diode

D1

D.A.A.

MH884XX

Circuit to meet UL1459 (50A.19)

MH88422

D1 = 190V

Teccor P2000A

MH88435 & 437

D1 = Teccor P3100SB

or P2703SB

Tip

Ring

MH8843X

To The Network

470H

470H

2200pFX7R

3kV

2200pF

X7R3kV

= earth (ground)

TIP

RING


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International standards are in operation for the line isolation, the most common being IEC 950, which is adopted

as EN60950 in Europe and UL1950 in North America. This defines categories of levels of isolation which must be

provided.

Note: In order to meet functional requirements the DAAs AGND may need to be connected to earth. The main

purpose of this is to reduce 50/60 Hz common mode signals which are associated with floating power supplies.

2.1.7 RFI/EMC and Power Supply Design Considerations

All of the DAAs mentioned in this application note will have to be protected from RFI(EMC) radiations that might be

generated by the PSTN. In some instances this may be a mandatory requirement, but in general failure to protect

the terminal equipment may result in the degradation of functionality of the DAA. RFI filters should not pass

frequencies above 150kHz, and should be fitted as closely to the telephone socket as possible (Figure 4 shows a

typical low pass configuration). The dielectric of the capacitors used must be able to withstand 1k5V, since these

will form a path to ground.

Even with the filters in place, the design and layout of a line card can still have a great effect upon

functionality with respect to noise and power supply interface. Care should be taken that other interface lines into

the application do not route unwanted RFI or transient noise that will be coupled across to the Tip and Ring lines.

This will prevent the degradation of the signal being received from the network.

Power Supply switching noise should be kept to a minimum, and power distribution to fast switching needs to be

via a low impedance path, with adequate local current sourcing available. The supply lines to the application

hosting the DAA should not have RFI levels present which exceed 100m Vrms over the frequency range 150kHz to

1000MHz.

Table 1 - Zarlink Semiconductor D.A.A.s

Note 1. Meets requirements of France and Germany in addition to the country requirements the MH88435 meets.

3.0 Zarlink Semiconductor DAAs

Zarlink Semiconductor DAAs have been designed to work as plug in modules, simplifying system design and

reducing overall cost.

They have developed along with changing standards and transmission speed and are still evolving. Table 1 shows

a summary of the key differences between the various product families.

Key Features MH88422 MH88435 MH88437

Reinforced Barrier 3

Supplementary Barrier 3 3

FCC Pt 68 isolation 3 3 3

Integral Loop Switch 3 3 3

Maximum Data Rate 9k6 33k6 (56k) 33k6 (56k)

Full Duplex Voice Capability 3 3

On Hook Reception 3 3

Programmable Impedances 3 3

Country Variants 3

Programmable DC characteristics 3 Note 1


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The family of products is continually being added to. We recommend that you contact Zarlink Semiconductor or one

of our representatives or distributors for latest information on available products, visit our Web site first.

4.0 MH88422 Data Access Arrangement

Device Description

The MH88422 is a DAA designed for V.29 applications where a reinforced barrier is required. It provides the 3kV

isolation barrier, 2-4 wire conversion function, the loop switch and is supplied as country specific variants as shown

below.

The device is a 26 pin Dual in Line packaged product.

4.1 General Considerations

The MH88422 has been designed to minimize the number of external components which are needed. As a

minimum the components shown in Figure 5 will be needed.

D1 is for protection from high voltage spikes, particularly from lightning strikes. C1 is a decoupling capacitor, to

remove unwanted noise from the power supply. C2 forms part of the dummy ringer circuit.

A dummy ringer is needed in order to provide the correct ringer load to the network, a load which varies between

countries. The resistive element of the dummy ringer is on board the MH88422, but this can be altered externally by

modifying the load between tip and ring. Refer to the relevant regulatory specs for different dummy ringer

requirements.

4.2 Applications Example

Security System

Warden Call and Security Systems often use dial up modem technology to provide data transfer capability to a

variety of different networks.

Device # Countries

MH88422-1 Germany (1TR2), Spain, Australia, Switzerland,

South Africa

MH88422BD-1 Germany (ZV5)

MH88422-2 North America, Far East and other countriesusing 600W

MH88422-3 United Kingdom, New Zealand

Note: The relevant country approval specification must be checked toverify compliance of the MH88422 part.


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Figure 5 - Typical MH88422 Application Circuit

Typically such a system would, in the case of an emergency, first dial the security service provider, often the Police,

or medical assistance. This is done through the following sequence of events:

1. The terminal moves from the on hook state to the off hook state through the closing of the loop switch inthe DAA.

2. Once dial tone has been detected a call will be made by transmitting DTMF tones to the Central Office or

PABX.3. If a busy tone is detected or call not answered then the sequence will be aborted through moving back to

the on hook state and the call will recommence.

4. When the call is answered and an acknowledgment is received the terminal will move to a data transfermode, when information on the nature of the emergency will be transmitted to the control centre.Appropriate action will then be taken.

A call can also be initiated from the control centre in order to interrogate the terminal, ensuring that it is functional

and down loading software upgrades. If this is the case then the MH88422 will detect the ringing signal allowing the

controlling processor to take the terminal off hook and receive the data transfer.


Figure 6 shows a typical set up for an application with a phone connected in parallel for Germany.

Transmit gain adjustment is provided by resistors R3 and R4. The gain is calculated using the following equation:

GainTx = 20log[R4/(R3+R4)] -0.4dB

Note, (R3 + R4) > 2k

TIP

RLS

TF

TXIN

RING

VX

VR

RVLC

LC

AGND

VDD

TIP

RING

C1

+5V

1

3

5

7

11

13

16

18

20

24

26AudioInput

Audio

Ring Voltage & LoopCurrent Detect Output

Loop Control Input

MH88422

+

R3

R2

R1

Protection

Circuit

Output

C3

C4

C2

Notes :

1) R1, R2: Transmit Gain Resistors2) R3 : Receive Gain Resistor3) C1 : 10F 6V Tantalum4) C2 : Dummy Ringer Capacitor5) C3, C4 : 10F AC coupling Capacitors

6) D1 Protection Circuit : See 2.1.5

D1

= earth (ground)
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Receive gain is set by R5. The receive gain is calculated using the following equation:

Gain Rx = 20log [47k/(47k+R5)] +3.5dB

These resistors must be fitted to prevent overloading of the output signal.

Figure 6 - Typical MH88422BD-1 Application

4.2.2 Ringing detection

The MH88422 provides the circuitry required to signal the presence of the ringing signal. The ringing signal

detection threshold and dummy ringer loads are defined in the relevant regulatory standards.

The MH88422 variants are designed to meet certain regulatory requirements for ringing detection by simplyconnecting together the relevant pins on the device and using a specified dummy ringer capacitor. However, the

user can adjust the threshold and dummy ringer load by using external components.

In Figure 6, R2 is shown fitted; this component allows external adjustment of the Ring detection threshold level. By

fitting R2 in parallel with R1 the ring detection level is increased from the minimum level quoted in the data sheet.

When choosing the value for R2 it should be noted that R7 and C2 which form the dummy ringer will also affect the

detection threshold value.

Note: Zarlink Semiconductor recommends consulting the regulatory standards and engaging the service of an

approvals testing facility before attempting to adjust the dummy ringer and ringing detection thresholds.

NOTES:

R3 = R4 = 2K2 (Typical value)

R5 = 100K (Typical value)

R6 = 200R - used to set parallelphone detection threshold

C1 = 10F 6V

C2 = 470nF

C3 = C4 =10F 10V

C6 = C7 = 22nF @ 16kHz

L1 = L2 = 4.7mH

D1 = Foldback Diode,

P2000AA61 (Teccor),

D2 = 1N4004

K1 = Electromechanical relay -

Must be compliant with reinforcedbarrier requirements. (K1a changeover

K1b normally open).

R2 = Ring Detection thresholdadjust resistor

Tip

PABX

Ring

D1

R6

K1a

R2 L2

C7

C2

L1

C6

D2 K1K1b

Tip Vx

RLS

MH88422 BD-1

Vr

TXIN

TF

RVLC

LC

VDD AGND

Microprocessor

R3 C4

R4

R5

+5V

C1

Modem

Data

Pump

+

+

+

C3

C7 = 29nF @ 12kHz

= earth (ground)


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5.0 MH88435& MH88437 Data Access Arrangements

Device Description

The MH88435/7 are DAAs designed as Telecom Network Voltage (T.N.V.) circuits for V.34 and V.34+ applications

where a barrier is required to comply with the supplementary barrier requirements of EN60950 and UL1950.

In addition to the isolation, the MH88435/7 provide the 2-4 wire conversion function and an integral loop switch.

Additionally the MH88435/7 have been designed to meet the network requirements of most administrations

worldwide and can be programmed to meet various line impedance and balance networks and DC templates.

The MH88437 is a superset of the MH88435 in that it will meet the same country requirements and in addition meet

specific requirements for France and Germany. These are detailed in the respective data sheets.

The devices are 28 pin Dual in Line packaged products and are available in surface mount or through hole format.

5.1 Device Set up and Programming

The MH88435/7 have many programmable features and these are described below. The set up of the ringing

sensitivity, line impedance, gain and protection circuits are implemented in the same way as was described for the

MH88434.

The programming of line impedance is done by connecting a network from ZA to ground. A table of networks

suitable for many countries is shown in Table 2.

An approximate value for other countries can be found by using the calculation given in the data sheet.

Zin = Zext + Zint

10

where Zext = external network connected between Za and AGND and Zin = 1.3k (internal resistance).

Refer to Table 2.

5.1.1 DC Mask Programming

The DC conditions which must be adhered to vary depending upon the country in which the DAA is being used. For

this reason the MH88435/7 can be programmed with the use of resistors outside of the device. This programming

feature should rarely be needed but provides the user with the flexibility to meet almost any requirement. France

requires that the loop current drawn by the DAA does not exceed 60mA, the MH88437 must be used to achieve this

where this feature can be met by setting CL to logic 0. The current limit is also required for CTR21.

5.1.2 Network Balance Impedance

The Network balance impedance is set by connecting a network between the NB1 and NB2 pins. Failure to

correctly match the network balance impedance will result in a degradation of the Trans Hybrid Loss performance

and as a result data transmission capability.

If the balance impedance is the same as the line impedance then a 15k resistor should be connected for the

MH88435, or a 16k resistor should be connected for the MH88437. For values which differ from the line

impedance then the correct network should be selected. Table 2 shows some typical network requirements.


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Table 2 - Programming Components

Note 1. For the MH88435 this value is 15k while for the MH88437 this value is 16kNote 2. Use MH88437 for this countryNote 3. NF = Not FittedNote 4. For the MH88435 this value is 2k0 while for the MH88437 this value is 910R

5.1.3 Detection of Line Reversals

If the detection of line reversals is required, the use of the circuitry in Figure 7 will be required. LR will be at +5V

when the polarity of the loop is positive forward battery and 0V when the loop is in reverse battery.

IC1 = LM339

Figure 7 - Line Reversal Detection Circuit with Connections to the MH88435/7 shown


The transmit gain of the MH88435/7 is 0dB. Transmit gain adjustment is provided by resistors as shown in Figure 8,

which form a simple potential divider. The gain is calculated using the following equation:

Gain Tx = 20 log R4/(R4 + R3)

Rpext Rsext Cpext ZOUT ZBAL RNS1 RNS2 RNP CNP

0R 4k7 NF 600R ATT Compromise 8K2 2K2 2K0Note 4

33nF

7K5 1K4 15nF CTR21Note 2

Equal to Zout 16K 0R NF NF

8K2 910R 10nF GermanyBAPTZV5

Note 2

Equal to Zout 15KNote 1

0R NF NF

0R 4K7 NF 600R 600R 15k

Note 1

0R NF NF

5K1 2K2 33nF UK BS6305 Equal to Zout 15kNote 1

0R NF NF

8K2 820R 15nF France*1Note 2

16k 0R NF NF

= earth (ground)

-

+

LR

+5V +5V

15K

Pin 11Loop

Pin 10VBIAS

IC1
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Note: (R4 + R3) >2k. Unlike the MH88422 and MH88434 these components do not need to be fitted unless gain

adjustment is required.

The receive gain is also 0dB, but can be adjusted by fitting R5 & R6. These resistors are in series with the device

input impedance, formed by the input resistors for VR+ & VR- feeding into an amplifier stage. The value for R5 and

R6 must be equal when used in a differential mode. The formula for calculating the gain is:

Gain Tx = 20 log 47k/(47k + R5).

It is usually not necessary to set the gain externally as this can be done through the modem chip set in which case

R5 & R6 are not fitted.

Figure 8 - Typical Application Circuit

TIP

NB2RING

VX

VR+

RV

LC

AGND

VCC

TIP

RING

C2

+5V

9

8

6

16

5

3

28

AnalogInput

Analog

Ringing Voltage Detect Output

Loop Control Input

MH88437

+

OutputC4

C1

Notes:

R1 & C1: Dummy Ringer, country specific

ZA

7

Zext

R2: DC Mask Resistor 82 k typical

R1

25 24

VLOOP1

VLO

OP2

VR-4 Analog

Input

R2

LCD 15Loop Current Detect Output

NB1

ZB: Network Balance Impedance

R3

R5

R6

R4

R5 = R6: Receive Gain Resistors typically 100 k

R3 & R4: Transmit Gain Resistors 2 k2

C3 +

10

VBIAS

typically 0.39 F, 250 V & 3 k

C2 & C3 = 10 F 6 VC7 & C8 = 39 nF for 12 kHz filter and 22 nF for16 KHz filter. These can be left off if meter pulse

filtering not required.Zext: External Impedance

D1 Zener Diode 9V1 (x2)L1, L2 = 4.7mH RDC


12/17



5.1.5 The Loop Pin

The loop pin output voltage, VLOOP, is proportional to the line voltage across Tip and Ring V(t-r), scaled down by a

factor of 50 and offset by VBIAS which is approximately 2.0V.

The formula is therefore:

V(t-r) = (VLOOP - VBIAS) x 50

6.0 MH88437 Data Access Arrangements

There are some differences between the two DAAs which are detailed further in this section.

6.1 Device Differences

The MH88437 is a pin for pin compatible part with the MH88435. In addition to the features of the MH88435, the

MH88437 will:

Meet the French current limit specification of 60mA

Meet the German dial pulse requirement of BAPT 223 ZV5

6.2 Device set up and programming

The programmable features of the MH88437 are the same as the MH88435, the only exceptions are:

Network balance impedance components are as defined in Table 2.

A pin previously not used, CL, is used to control the French current limit. For countries not requiring thisfeature the pin should be set to logic 1.

For details on the countries that the MH88435/7 are suitable for, please refer to the individual data sheets.

7.0 Using the MH88437 DAA with CTR21

As of July 20th 1998 TBR21 became CTR21, giving mandatory access to the PSTN data applications in all EC

countries (plus Finland, Iceland, Israel, Norway and Switzerland). Even though this CTR is enforceable for terminal

equipment, the document has no scope to alter the equipment within the Central Office in each of these countries,

that will eventually interface with your application. This leads to many problems for designers who wish to use

CTR21 as a common licence for connection in Europe.

To aid a design using this approach into Europe Zarlink advise that, applications using the MH88437 are still

designed to meet the country specific specifications, in addition to the CTR21 document. This is necessary due to

the many different AC and DC termination requirements.

The line conditioning components below (Figure 9) when used in conjunction with the logic table 2, are capable of

providing regulatory approval to the standards listed for each country.

7.1 Points of Note when Designing for CTR21

1. CTR21 has no provision for equipment utilising Pulse or Loop Disconnect dialling. Any application declaring its

use in countries other than Holland and Switzerland will have to adopt the national route for approval.

2. When designing an application for use with CTR21, refer to the advisory notes EG201 121 issued by ETSI.

Although these notes are not a legal requirement their content is informative.
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13/17



3. Finland, Iceland, Israel, Norway and Switzerland are not members of the EC, but they have chosen the to align

themselves to CTR21. This means that each of them can choose the test house that they will accept a report

from. Before beginning the process of approval to CTR21 it is prudent to investigate which test houses can issue

a recognised report for these countries.

4. To pass the Norwegian National DC mask using the application circuit (Figure 11), L1 and L2 should be replaced

with 0 links.

5. CTR21 makes no mention of Meter Pulse Filters but under both the German and Swiss national requirements, a

high impedance to 12kHz and 16kHz meter pulses is mandatory. The value of RDC for L1 and L2 should be


14/17



Figure 9 - Output and Network Balance Impedance Setting Networks

Table 3 - Programming Conditions for Various Approvals

Table 4 - Programming Conditions Advisable for Additional Country Approval

Country Approval Spec. CL SW1 Position

Denmark CTR21 0 2

France B11 23A 0 1

Germany BAPT223 ZV5 1 2

Holland T11 1 1

Luxembourg CTR21 0 2

Switzerland SR.784.103.12/2.2 1 2

Sweden CTR21 0 2

U.K. CTR21 0 2

Country Approval Spec. CL SW1 Position

Finland NET 4 0 1

Italy NET 4 1 1

Norway NET 4 1 2

Spain CTR21 0 2

Portugal NET 4 1 1

NB 1

NB 2

ZA

Rpext Cpext

RNS1

RNS2CNP

RNP

MH88435/7

Rsext

= earth (ground)


15/17



Figure 10 - MH88437 V/I Characteristics During Current Limit (shown with CTR21 Mask)

X

X X

X

(14.1,4.8)(21,6.2)

(43,13)

(56,37)

MH88437 Response

40V

4.5

9

020 42 50 60


16/17



Figure 11 - CTR21 Application Drawing (with a 600R Option and Meter Pulse Filters)

15k

220k

70k

1 2

SW1

750R

15nF6k24k7

ZA

LOOP

RS

NETBAL 2

NETBAL 1

CLTip

Vloop1

Vloop2

Pin21Pin 22

Ring

175pF

L1 = 100uH

0.39uF C1

6V2 CR1

3k9 R1

MH88437

To PSTN

= earth (ground)

TIP

RING

C1

C2

0.1uF

L2 = 100uH

9V1


17/17

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