Selection and Testing of Electronic Components for LM

ERICSSON 

REVIEW 

3 

1977 

SELECTION AND TESTING OF ELECTRONIC COMPONENTS 

CROSS STRANDING OF TELEPHONE CABLE 

NEW TELEPHONE SET 

DIGITAL LINE EQUIPMENTS 

OPERATION AND MAINTENANCE CHARACTERISTICS OF AKE 

MAGNETO SWITCHBOARD

ERICSSON REVIEW 

NUMBERS 1977 -VOLUME 54 

Copyright Telefonaktiebolaget LM Ericsson 

Printed in Sweden, Stockholm 1977 

RESPONSIBLE PUBLISHER DR. TECHN CHRISTIAN JACOB/EUS 

EDITOR GUSTAF O. DOUGLAS 

EDITORIAL STAFF FOLKE BERG 

EDITOR'S OFFICE S-12625 STOCKHOLM 

SUBSCRIPTION ONE YEAR $6.00ONE COPY $1.70 

Contents 

94 • Selection and Testing of Electronic Components for LM Ericsson's 

Telephone Exchanges 

105 • Cross Stranding of Telephone Cable 

112 • New Telephone Set 

114 Digital Line Equipments for 8 Mbit/s and 2 Mbit/s 

125 • Operation and Maintenance Characteristics of AKE 13 

136 • ABJ 101-the Modern Public Magneto Switchboard 

COVER 

Part of a memory board with electronic components. 

In the foreground a capacitor manufactured 

by AB Rifa — an Ericsson company.

Selection and Testing of Electronic 

Components for LM Ericsson's 

Telephone Exchanges 

Berndt Agneus and Ivan Borgstrom 

Electronic components have formed part of automatic telephone exchanges for 

a rather long time. The rapid development that these components, primarily micro 

circuits, have experienced during recent years and which can be expected to continue 

for a long time is of great importance for the design of new exchange systems. 

In fact, the new systems are in the main based on electronic components. In the 

design work it is essential to select components that not only have the desired 

function but which are also stable during the estimated life of the exchange. The 

article deals with various activities, which together are aimed at ensuring the correct 

range of components for telephone exchange equipments. The illustrations 

with captions provide information regarding various aids that are used in this connection. 

The article also gives a summary of electronic components of current 

interest and their probable development trends. 

UDC 621.3.049.7 Component categories 

Electronic components for LM Ericsson's 

telephone exchange equipments 

are to a certain extent manufactured 

within the group. The remainder are 

bought externally and usually belong to 

the suppliers' standard ranges. In certain 

cases, however, components are required 

with characteristics that necessitate 

either special selection from the 

standard range or the introduction of 

special "customer adapted" components. 

The component quality corresponds 

to the category "professional 

components", which meet higher reliability 

and long-term stability requirements 

than so-called entertainment 

components. 

Electronic components are usually divided 

into three main categories as regards 

their function, namely passive 

components (resistors, capacitors etc.), 

discrete semiconductor components 

(such as diodes, transistors and 

thyristors) and various types of micro 

circuits, see fig. 1. 

The importance of the 

components in the system 

design 

The design and characteristics of an exchange 

system are to a great extent dependent 

on the design of the components. 

There is in fact mutual effect 

since the system design influences the 

design of the components. 

LM Ericsson's "great" automatic 

systems, the 500-line selector system 

and the crossbar system, were both 

based on electromechanical components. 

However, electronic components 

were also included in these systems at 

an early stage. They were then mainly 

used for secondary functions such as 

series and parallel resistors, delay 

capacitors, CR units for contact protection 

etc. These components were often 

soldered on to tags on the relays. 

The electromechanical systems have 

been modernised extensively as and 

when the need has arisen. In connection 

with this, discrete components (first 

discharge valves, later on diodes and 

transistors) were brought into use at 

quite an early stage. They were then included 

in such function units as test 

circuits, MFC signalling systems and 

charging units. 

SPC technique (Stored Program Control) 

was first used in LM Ericsson in the 

transit exchange system AKE 13, and 

was then based on diodes, transistors 

and ferrite memories. Fast micro 

circuits, including semiconductor 

memories, became important for the 

further development of the SPC technique. 

Micro circuits are now primary elements 

in modern exchange systems. They require 

very little space in relation to the 

large number of logic functions they are 

able to perform. They are usually 

mounted on printed circuit boards, 

which makes for a compact construction 

throughout. Reed switches, miniature 

relays and certain other components 

have also been adapted for 

mounting on printed boards. 

The development of components and 

systems continues in close collaboration. 

The need for such development 

collaboration will increase as complex 

"components" containing very large 

numbers of functions are introduced. 

An example of such "components" are 

microcomputers, which in one or a few 

micro circuit packages accommodate 

the primary functions of a computer. 

Principles for the selection 

of electronic components 

Components in telephone exchange 

eauiartiants musLhe_abJe to perform the

BERNDTAGNEUS 

Älvsjö Electronics Factory 

IVAN BORGSTRÖM 

Telephone Exchange Division 

Telefonaktiebolaget LM Ericsson 

Fig. 1 

Column 1 (lett) 

Some types of resistors and capacitors (passive 

components) 

(From top to bottom) 

Plastic foil capacitor with epoxy cover 

Tantalum capacitor, dry type 

Attenuator In the form of thick-film resistors on a ceramic 

substrate 

Varnished film resistor 

Column 2 

Discrete semiconductor components 

Display of the 7-segment type 

Light-emitting diode for visible light 

Transistor In TO 18 metal case 

Rectifier diode in a glass envelope for 1 A 

Fast logic diode In a D 35 envelope 

Column 3 

Micro circuits 

Programmable memory in a 24-pin DIL ceramic and metal 

package 

Digital micro circuit In a 16-pln ceramic Dual-in-Llne (DIL) 

package 

Linear micro circuit in an 8-lead metal envelope 

intended task with high reliability during 

the whole life of the equipment. In 

addition to this basic requirement a 

number of other important factors must 

be taken into consideration when 

selecting electronic components, in order 

to obtain a suitable range of components. 

Among these may be mentioned: 

Technical status and trend. Is the component 

based on a new technique or 

new materials? If so, how well is the new 

technique developed and how well are 

the characteristics defined? Is the development 

likely to proceed towards the 

type represented by the component, or 

in other words has it got a future? 

Supply. Since electronic components 

are to a great extent purchased from different 

manufacturers it is important to 

know which manufacturers are able or 

will be able to supply a particular component. 

For reasons such as supply reliability 

it is essential that there will be 

several approved suppliers for each 

type of component. 

95 

Need. The current and future need for 

the component is investigated in collaboration 

with circuit and system designers. 

The quantities used affect supply 

and price. 

Price situation and tendency. A comparison 

with alternative components or 

circuit designs is made in order to assess 

the financial side of the component 

selection. 

Standardization and coordination. It is 

in the interests of both LM Ericsson and 

the customers that the range of components 

used in equipments is limited, so 

that the number of different items is not 

greater than is absolutely necessary 

with regard to the function and reliability 

requirements. Consequently the introduction 

of new components requires 

that the proposals by component 

specialists are submitted to special 

standardization committees for decision. 

Component selection and policy 

questions of particular importance are 

referred to a component council.

Fig. 2 

Curve tracer 

The special type of oscilloscope, which is called a 

curve tracer, Is a universal Instrument tor testing 

semiconductor components. A family of curves are displayed 

on the screen. These give an overall picture of the 

electrical characteristics of the component. The curves 

can provide Important data, such as amplification factor, 

breakdown voltage and reverse current 

Fig. 3 

Light microscope 

Microscopes are valuable aids in construction and fault 

analyses of electric components. By means of direct 

observation or photography using light or electronic 

microscopes It Is possible to study and assess the design 

of component details or determine the causes of faults. 

Mlcroscoplng is indispensable when studying intricate 

conductive patterns or wire bondings on semiconductor 

crystals 

Coordination between different divisions 

and companies in the Ericsson 

Group in questions relating to choice of 

electronic components takes place, for 

example, through a special component 

and circuit committee, within specialist 

groups and through centrally distributed 

component information. 

Rules for use. The conditions that are to 

apply for the use of the new component 

in circuit designs are considered in 

connection with the component selection. 

In order to attain the desired reliability 

and life it is often necessary to reduce, 

to a greater or lesser extent, the 

values given in the manufacturer's 

component data for permissible electrical 

loads and operating temperatures. 

Permissible design data are given in 

special documents which also contain 

additional information for the designers. 

Production engineering aspects. When 

manufacturing equipments it must be 

possible to check, assemble and connect 

the components using rational 

methods and production aids. This 

means, for example, that questions 

concerning automatic assembly, soldering 

and cleaning of components 

must be considered. 

Current component range 

Equipments belonging to different exchange 

systems, which have been designed 

at different times, are manufactured 

continuously and often in parallel. 

The components have been selected 

during different development epochs. 

In order to prevent this from having any 

negative effects the component range is 

continously standardized and modernized. 

The most important types of passive 

components, discrete semiconductor 

components and micro circuits used in 

the LM Ericsson exchange equipments 

are described below. 

PASSIVE COMPONENTS 

Passive components comprise various 

types of resistors, capacitors and transformers. 

Resistors 

Carbon film resistors constitute the 

most common type. The resistive element 

consists of a carbon film on a 

ceramic rod. Operational experience 

has shown that the carbon film resistor 

is the most reliable type of component 

in telecommunication equipment. 

In addition to carbon film resistors, 

metal film resistors are used where low 

temperature dependence is required. 

This type of resistor is being used to an 

increasing extent in electronic equipment. 

A third type of film resistor that has recently 

been introduced is the metallic 

oxide resistor, where the resistive element 

consists of tin oxide with antimony 

oxide added. 

Thick-film resistors, manufactured by 

means of screen printing and firing a resistive 

paste on to a ceramic substrate, 

are used as attenuators and fuse resistors. 

Capacitors 

This category of component includes 

many different types, whose characteristics 

and thus fields of use are mainly 

determined by their dielectric. 

Aluminium electrolytic capacitors of the 

long-life type are used for regulating the 

operating times of relays. In this case a 

large capacitance per unit of volume is 

an essential characteristic. 

Tantalum electrolytic capacitors are 

usually chosen for electronic circuits 

when the requirements are small size 

and moderate capacitance values at low 

voltages. 

Polyester film capacitors are being used 

to a great extent nowadays in transmission, 

time and contact protection 

circuits instead of the traditional paper 

capacitors 

Polystyrene capacitors are used when 

close tolerances and good stability are 

required, for example in tuned circuits. 

Both polystyrene and polyester film 

capacitors are manufactured with a 

moulded epoxy cover and are constructed 

for mounting on printed 

hoarriffc nnfi lion irt ralnw QjatQ

Fig. 4 

X-ray camera 

The Inner construction and manufacture of components 

can be of great importance to function characteristics and 

life. One way of Investigating the Inside of the component 

Is to open the case and cut through the component. However, 

this method Is usually destructive, so that the component 

properties are changed entirely. 

It Is often possible to obtain valuable Information regarding 

the structure of the component by means of an X-ray 

photograph. Inner mechanical faults can also be detected 

on such pictures. In addition the possibility remains of carrying 

out supplementary electrical measurements on the 

unaffected component after the X-ray Investigation 

Fig. 5 

Desk calculator 

Agreatnumber of measurements.provldlng large amounts 

of measured values, are often carried out In connection 

with component Investigations. These values must be processed 

In order to obtain essential data in a clear form. A 

desk calculator is used for this purpose which can be programmed 

to process the test material In a suitable way and 

give the result as a printout or on a diagram. The desk 

calculator Is also used for certain component data calculations, 

for example when dimensioning transformer wind- 

Transformers and inductors 

Transformers with a core of plate 

frames or tape are used in transmission 

circuits that transmit alternating current 

superposed on a direct current. 

Ferrite transformers with different types 

of cores, in certain cases adjustable, are 

used as current transformers and for 

filtering in power equipment, in tuned 

circuits and oscillators, for impedance 

matching and pulse transmission. 

DISCRETE SEMICONDUCTOR 

COMPONENTS 

These components contain individual 

semiconductor components, each of 

which performs just one single function. 

They are still used in modern exchange 

systems along with micro 

circuits, and consist mainly of transistors 

and diodes, but thyristors and 

optical semiconductor components are 

also included in this category. 

Transistors 

All modern transistors are made of silicon 

and usually manufactured by 

means of so-called planar technology. 

For quality reasons a metal can with 

glass lead-throughs for the conductors 

is used. 

Diodes 

The diodes used in exchange systems 

97 

can be divided into three main 

categories: rectifier diodes, switch 

diodes and voltage regulation diodes. 

The switch diodes are used in logic 

circuits and must therefore have a short 

recovery time in the reverse direction. 

The voltage regulation diodes give a defined 

voltage level in circuits where a 

stable reference voltage is required. 

Special semiconductor components 

Among semiconductor components 

that are used to a limited extent for special 

functions may be mentioned the 

thyristor, which closes a circuit when a 

pulse is applied to its gate electrode, 

and the unijunction transistor, which is 

used for starting time circuits and 

thyristors. 

Opto-electronic components have recently 

been introduced that use visible 

or infra-red light for their operation. 

Among them are light-emitting diodes, 

displays and opfo couplers. 

Red, yellow and green light-emitting 

diodes are used for indicating different 

states in equipments, and displays 

show a figure or a letter depending on 

the applied electrical signals. 

The opto coupler, on the other hand,

Fig. 6 

Humidity test 

High air humidity Is one of the most serious adverse environmental 

conditions to which electrical components 

can be exposed. The dampness can affect the outside of 

the components by corroding metal surfaces and reduce 

the Insulation between the leads. It can also seep Into the 

components and In so doing impair their caracterlstlcs or 

cause total breakdown. 

Humidity testing Is carried out in an climatic chamber, 

where the air humidity and temperature are either 

held constant or varied cyclically with time. The components 

can either just be stored In the chamber or they 

can also be connected to an electrical voltage source 

during the humidity tests 

Fig. 7 

Programming equipment 

In a certain type of semiconductor memories, designated 

PROM (Programmable Read Only Memories), the contents 

of the memory cells are fed In with the aid of special programming 

equipment A metallic connection is thereby 

burnt off electrically in the cells that are to be programmed. 

The memory program can be fed in in different ways: 

manually via a push-button set, from a punched tape or 

with the aid of a previously programmed memory (master). 

The equipment also checks that the programming Is correct 

uses infra-red lights as the transfer 

medium between a light-emitting diode 

and, for example, a photo transistor. 

MICRO CIRCUITS 

Micro circuits are built up of a number 

of interworking semiconductor elements 

and can integrate a number of 

analogue functions, digital functions or 

memory functions. 

Analogue micro circuits 

In analogue circuits the voltages on the 

inputs and outputs can vary continuously 

over certain ranges and are thus 

not limited to fixed levels. In modern exchange 

systems these circuits are used 

as 

— voltage regulators for power units 

— sensors of voltage levels 

— interface circuits between different 

subsystems 

— operational amplifiers in MFC filters 

etc. 

Digital micro circuits 

These circuits are predominant among 

the micro circuits. Digital circuits carry 

out logic operations by means of digital 

signals, i.e. voltages on the inputs and 

outputs that take up values close to 

fixed levels. Many of these circuits belong 

to specific so-called circuit 

families with a certain type of logic element 

and in other respects designed so 

that they can interwork in systems. 

In addition to these circuit families a 

number of digital circuits are used that 

do not belong to any particular family. 

These can be divided into a number of 

groups according to function, such as 

registers, adders, arithmetic circuits, 

counters, data switches, coders and decoders. 

DTL circuits (Diode-Transistor-Logic) 

constituted one of the first families in 

micro circuit technique. They are no 

longer used when designing new 

equipments. 

TTL circuits (Transistor-Transistor- 

Logic) are faster than DTL circuits and 

have gradually become the predominant 

type. 

A large number of circuits are available 

on the market in several different variants. 

Certain series (e.g. 74S and 74LS) 

have integrated so-called Schottky 

diodes, whereby the circuits have been 

made faster. 

CMOS (Complementary-Metal-Oxide- 

Silicon) circuits operate within wide voltage 

limits and have low power consumption, 

but they are not particularly 

fast. 

Memories constitute an important 

group. They can be in the form of random 

access memories, where the con-

Fig. 8 

Load test 

Electrical load tests over a relatively long period (several 

thousand hours) constitute an Important part of the type 

testing ot components. For these tests the components 

are mounted on printed wiring boards placed In racks, 

which when necessary are equipped with supervisory 

equipment that records component faults. The electrical 

load Is often Intermittent, i.e. It Is switched on and off at 

certain Intervals In order to Imitate the stresses that can 

occur In some operational cases. At certain times the 

components are removed In order to measure their 

electrical characteristics. 

The lead tests provide Information regarding changes In 

the component data during operation (ageing), and In certain 

cases regarding probable failure rate and life 

Fig. 9 

Cold test 

Exchange equipments do not normally need to work at 

temperatures below the freezing point. However, during 

transport in cold areas they can be exposed to low temperatures, 

which they must be able to withstand without 

damage. The electrical components are therefore tested 

at temperatures down to at least — 40°C. 

In a corresponding way the effect of high temperatures Is 

• • . . . . . . - . . - - ••• • 

tent can be changed, or read only memories 

with fixed content. Both the fast 

bipolar semiconductor technique and 

the less power-demanding MOS technique 

are used for memory components. 

Special circuits 

The above-mentioned micro circuits are 

of standard design and can be bought 

from different suppliers. However, for 

certain purposes it may be appropriate 

to introduce special circuits that satisfy 

particular function requirements. 

Packaging 

Micro circuits are usually packaged in 

ceramic cases with the external pins 

arranged in two rows, so-called DIL 

packages, although certain types of 

analogue micro circuits are packaged 

in cylindrical metal cans. 

Type testing 

The purpose of type testing is to determine 

whether a certain type of component 

from a manufacturer satisfies 

the given data and requirements. The 

type testing comprises measurements 

of data, function checks, environmental 

tests and load tests. 

The actual type testing is usually preceded 

by a preliminary investigation, 

which comprises the study of available 

99 

information concerning the type of 

component and a construction analysis 

of a small number of test items. Such 

methods as X-ray photography, dissection, 

microscoping and material analysis 

are used to investigate and assess 

the packaging and sealing, internal 

connections, metal and oxide layers, 

diffusion pattern, cooling and mounting 

and connection facilities. 

Type testing is carried out in accordance 

with programs that indicate 

which tests and measurements are to be 

carried out. As far as possible the type 

testing programs are based on the recommendations 

issued by the International 

Electrotechnical Commission 

(IEC). When necessary, additions and 

modifications are made in order to 

adapt the type testing to the special operational 

conditions of telephone exchange 

equipments. Thus particular 

importance is attached to the verification 

of the reliability and stability of the 

components during long periods on 

load. 

The type testing programs normally 

comprise cold tests, heat tests, temperature 

cycling and humidity tests in a 

constant environment and also with 

fluctuating air humidity and temperature. 

Moreover, the programs generally 

include vibration tests, soldering tests,

100 

Type of check 

Type of component Me- En- El. 

chan- viron- param. 

ical mental 

Resistors, resistor net 

works and potentio 

meters S S 

Capacitors 

Diodes, transistors 

S S 

and thyristors S A 

Micro circuits S A A 

Table 1 

Testing of components 

A Check of the whole consignment 

S Sampling test in accordance with MIL-STD-105 

Fig. 10 

The solderability tester STE 74 works in accordance 

with the solder globule method and is intended 

for measuring the solderability of components 

and metallized holes in printed boards etc. 

The test Item whose solderability is to be measured is lowered 

into a molten solder globule that is placed on top of a 

heated iron cylinder so that the globule Is divided into two 

equal parts. When the solder wets the test item the latter is 

completely enclosed by the solder. The wetting time is 

measured and Is a measure of the solderability of the test 

item. 

The lowering speed, solder temperature and quantity of 

solder are carefully specified. The solder and test item are 

treated with flux and the solder must wet the iron cylinder 

hermeticity tests, tension, bending and 

torsion tests on the leads and flammabil 

ity tests. Electrical tests may com prise 

voltage tests, current pulse tests and 

power loading tests. Such tests can 

continue for periods of 1 000 hours up to 

more than 10000 hours depending on 

the type of test and the "acceleration 

factor", i.e. the size of the load in relation 

to specified component data. 

Significant component data are measured 

before, during and after the 

course of the type testing. 

Type testing programs for electronic 

components also contain instructions 

for assessing the test results. However, 

the final decision as to whether a certain 

type of component should be accepted 

is always based on the expert knowledge 

of the component specialist. 

Quality follow-up 

Components delivered by approved 

suppliers are inspected on arrival in the 

way described in the next section. In 

addition a so-called reliability evaluation 

is carried out in accordance with a 

yearly plan, primarily of recently introduced 

components and components 

purchased in great quantities. 

The reliability evaluation provides a 

continuous verification that the com 

ponent quality originally accepted after 

type testing is maintained in later component 

deliveries. 

In this evaluation, which is carried out 

on samples taken from the deliveries, 

the inner construction of the component 

is studied and compared with reference 

examples from the type testing. 

It can then be ascertained whether the 

manufacturer has for example introduced 

a new type of silicon chip in a 

transistor or changed the connections 

to a capacitor foil. 

The reliability evaluation also includes 

a limited type testing for the purpose 

of finding any quality defects in a component 

consignment within a few 

weeks. It is then possible to prevent the 

use of unsatisfactory components in the 

production of exchange equipments. 

When a component fault is reported in 

equipment being manufactured, in the 

system testing stage or in operation, a 

fault analysis is carried out in order to 

determine the cause of the fault and 

when necessary to improve the component 

quality. 

Inspection of components 

on arrival 

Inspection of purchased components

Fig. 11 

on arrival takes place in accordance 

with test instructions based on IEC and 

MIL standards. The purpose of the inspection 

on arrival is to ensure that the 

components in the system meet LM 

Ericsson's high demands for reliability 

and long life. 

SCOPE 

The inspection on arrival is carried out 

on passive components, discrete 

semiconductors and micro circuits. It 

comprises checks of the mechanical 

properties of the components, their 

ability to withstand adverse environments 

and their electrical parameters. 

The checks are carried out either on all 

components or on a sample in accordance 

with table 1. 

101 

INSPECTION PROCEDURE 

All components are tested mechanically 

in the following way: 

Mechanical dimensions are measured 

with vernier callipers and the solderability 

checked by means of the solder 

globule method or the solder bath method 

at 230 ± 10°C (requirement of IEC 68- 

2-20). Fig. 10 shows a solderability tester. 

Resistors, resistor networks 

and potentiometers 

These are tested as follows: 

The resistance value is determined with 

the aid of a Wheatstone bridge. 

The harmonic distortion factor is measured 

with a distortion factor meter.

Fig. 12 

Computer-controlled test system for memory 

circuits, Macro-Data MD 104 M/MC 

Here equipped with a handler, which makes possible testing 

at Increased temperature 

Fig. 13 

Test system Tektronix S-3260 

Evaluation and checking of complex micro circuits both 

require such extensive measurements that special test 

systems are necessary. A minicomputer is used tor executing 

the test programs, which apply Incoming signals 

on certain of the component connections. At the same time 

measurements are made on the output connections. The 

test results are processed and are then shown on a display 

or as a printout 

Capacitors (excl. electrolytic 

capacitors) 

The capacitance value is measured with 

a comparison bridge, where the value is 

set up and the deviation is read off in 

percentage units. 

The dissipation factor is measured with 

a distortion factor meter. 

Voltage tests are carried out using a 

special voltage tester, which is set up 

for a certain voltage and which records 

the insulation resistance and any 

breakdowns. 

Electrolytic capacitors 

Capacitance, dissipation factor and 

leakage current are tested with a comparison 

bridge, where the capacitance 

and dissipation factor values are balanced 

out, after which the leakage current 

is read off on a special scale. 

Diodes and transistors 

The electrical parameters of these are 

measured using a go-no go tester with 

automatic input. SMall consignments 

are checked using a curve tracer. 

Micro circuits 

Micro circuits are subjected to rigorous 

checks comprising mechanical, environmental 

and electrical tests. The 

testing procedure is shown in fig. 11. 

The electrical testing of micro circuits 

deserves to be described more in detail. 

From the point of view of testing, the 

micro circuits can be divided into four 

groups, namely analogue, simple digital, 

complex digital and memory circuits, 

which require different types of 

advanced test equipment. 

Analogue circuits 

The parameters concerned are checked 

manually in test equipment type General 

Radio 1730. 

Simple digital circuits 

These are tested statically in test 

equipments type Teradyne J133 and 

Fairchild Q 901 "Qualifier".

Fig. 14 

Diagram of the fault ratios for micro circuits distributed 

on a manufacturer basis 

Leakage faults check position 1 

Electrical faults 

Leakage faults 


Cneck ,,,„„ 2 

Leakage faults 


check pos|tlon , + 2 

Different manufacturers 

Fig. 15, right 

Fault ratios for passive components and discrete 

semiconductors, obtained from computer system 

"Makon" 

Mechanical faults 


Complex digital circuits 

The circuits are tested from a functional 

point of view and also statically and 

dynamically. For this purpose the production 

side uses system Tektronix 

S-3260, which is shown in fig. 13. 

Memory circuits 

These are also tested as regards function 

and statically and dynamically. The 

test equipment used is Macro-Data 

M104 M/MC, shown in fig. 12. 

THE RESULTS OF INSPECTION 

ON ARRIVAL 

Inspection reports are kept for each individual 

inspection occasion. The reports 

are compiled once a month and 

the statistical data are processed with 

the aid of the LM Ericsson computer 

system MAKON (Material Control 

Purchase). Some results are shown in 

the histogram for micro circuits, fig. 14. 

The histogram contains statistics from 

two different inspection positions, 

where the inspection differs as regards 

the hermeticity test. In one place the 

trace gas used is krypton 85 and in the 

other helium. 

Fig. 15 shows the fault ratios for passive 

components and discrete semiconductor 

components. 

103 

FAULT TRACING COSTS-A 

COMPARISON 

Fig. 16 shows a comparison of fault tracing 

costs at different check levels. The 

figures are based on experience of 

actual costs. The diagram shows that it 

can be profitable to invest in more effective 

fault elimination methods in the inspection 

on arrival, forexample burn-in, 

in order to eliminate defective components 

that whould otherwise cause operational 

disturbances in the systems. 

FUTURE PROSPECTS 

Development of an effective and cheap 

method that makes possible a one 

hundred per cent check for gross leakages 

is desirable. Fine leakages in the 

encapsulation are then checked by 

means of sampling. Heat storage of 

components is replaced by burn-in with 

voltage applied and increased temperature. 

The increase in the complexity and 

speed of micro circuits requires large 

investments in systems for testing the 

functions and the DC and AC parameters 

during the inspection on arrival. The 

test system is equipped with a main 

computer that controls several check 

stations. The check stations for the inspection 

on arrival can work as independent 

units and utilize centrally prepared 

programs. Electrical function 

testing will to an increasing extent be 

carried out at an elevated temperature.

104 

Fig. 16 

Comparison of fault tracing costs at various check 

levels. (Micro circuits) 

Volume checked: 2 000 000 

Volume checked: 10000000 

Development tendencies 

The component development is at present 

progressing very rapidly, particularly 

in the field of micro circuits. There 

are already so many types of circuits for 

different purposes that existing demands 

for speed, low power consumption, 

insensivity to disturbances or voltage 

variations can usually be satisfied. 

However, because of the rapid development 

of micro circuits there has 

often been time for improved circuits to 

appear on the market during the period 

between the selection of components 

and the putting into service of the first 

example of a new system. It is desirable 

that it should be possible to exploit new 

achievements in the field of components 

in previously completed designs, 

for example by changing over to a new 

circuit family. 

The development of micro circuits leads 

to an increasing degree of complexity 

and flexibility. This means that the 

boundaries between components, units 

and subsystems are being wiped out. 

Programmable component types, such 

as micro processors and memories, will 

have a decisive influence on the design 

and performance of the systems. This 

also means that a greater part of the 

"knowledge" and flexibility of the exchange 

systems will be transferred from 

fixed hardware to changeable software. 

As regards memory components the 

development is towards greater capacity 

and speed. It is likely that the memory 

types that retain the information even in 

the case of voltage failures will become 

very important in future. 

It is also likely that selectors with 

mechanical contacts will to an increasing 

extent be replaced by electronic 

switching elements. Opto-electronic 

and purely optical components will also 

be very important for the transmission 

of information. 

Development of passive components 

follows in the wake of the applicable 

material and production engineering 

development in the semiconductor 

field. The resistors will be able to withstand 

higher voltages and will have 

smaller dimensions. There are already 

resistor networks that are mounted in 

micro circuit packages. It is also likely 

that plastic foil, oxide and ceramic 

capacitors will be improved.

Cross Stranding of 

Telephone Cable 

Sigurd Nordblad 

LM Ericsson have developed a new manufacturing process and constructed new 

machines for the manufacture of pair cables. The process, which is called cross 

stranding, combines two methods: twinning and stranding of groups in one operation 

and repeated changing of the relative positions of the pairs during the stranding. 

The changing can either be carried out systematically in accordance with a set 

plan or at random, so-called randomized cross stranding. The main purpose of the 

cross stranding is to reduce the extreme values of the crosstalk and thus improve 

the quality of the cable. 

In the article the cross stranding technique is described with the emphasis on the 

manufacture of pair cables with randomized changing, but cross stranding can also 

be used with advantage for stranding single conductors, triples, quads, quintuples 

etc. 

The cross stranding technique has now been introduced at most of the telecommunication 

cable factories owned by the Ericsson Group. At the Piteå plant, which 

wasstartedin 1972, the entire production is based on this technique. Manufacturers 

outside the Group also use the technique. 

UDC 621.315.2 

621.391.31 

Fig. 1 

Cross stranded cables 

Top, 150-pair cable with 25-pair groups 

Bottom, 50-pair cable with 10-pair groups, jelly- 

In addition to line attenuation, characteristic 

impedance and line resistance, 

the crosstalk characteristics of a cable 

have a very great influence on its field of 

use. This applies particularly in the case 

of trunk cables but also for subscriber 

cables. 

One reason why the subscriber cables 

of today should have a low level of 

crosstalk is that modern telephone sets 

can then be utilized more efficiently. 

The usefulness of a telephone set is limited 

by such factors as the crosstalk 

level in the cable network. A reduction 

of the crosstalk means that greater distances 

can be spanned or that the conductor 

size can be reduced. 

High frequency systems, which are used 

nowadays to an ever increasing extent, 

SIGURD NORDBLAD 

Sieverts Kabelverk AB 

also require cables with improved 


Previously the pairs, single conductors, 

quads etc. of a cable have usually been 

assembled in concentric layers. The 

pairs were then parallel in each layer 

and were adjacent to the same pairs 

along the whole length of the cable. 

Subsequently the unit cable was introduced, 

but the units were still built up of 

concentric layers. Efforts to improve the 

cable characteristics have been concentrated 

on improving the precision of 

the wire drawing, insulation etc. and on 

suitable selection of lay lengths, i.e. improvements 

within the pairs, and very 

little attention has been paid to the effect 

of the cabling method on the 


Crosstalk occurs mainly between adjacent 

pairs and it is obvious that the 

crosstalk increases when the pairs are 

adjacent over a long distance. Using the 

conventional layer stranding technique 

the pairs are placed adjacently and as 

close as possible along the whole 

length of the cable. The crosstalk level 

between pairs varies in a cable; high 

level between adjacent pairs and very 

low level between separated pairs. 

However, in a telephone system the 

worst values often constitute a technical 

limit and a number of very good values 

does not alter this fact.

Fig. 2 

Cable groups with the conventional lay-up 

Top, 10-palr group 

Bottom, 25-palr group 

Fig. 3 

Cross stranding lines 

Top, line lor manufacturing 10-palr groups 

Bottom, 25-pair line with drum twister take-up 

The principle of the cross 

stranding technique 

Cross stranding differs from the other 

stranding methods inasmuch as the 

pairs or other elements in question are 

assembled to form a group with the 

pairs continuously changing their relative 

positions during the assembly. This 

can be carried out in different ways. The 

elements can be assembled in groups 

either in accordance with a set pattern, 

systematic cross stranding, or at random, 

randomized cross stranding. 

Systematic cross stranding has the disadvantage 

that two elements meet at 

fixed intervals. In high frequency 

systems the intervals can correspond to 

wavelengths in the frequency range 

concerned, which can give rise to a resonance 

phenomenon that is difficult to 

eliminate. With randomized cross 

stranding the elements are crossed at 

random, which eliminates this resonance 

phenomenon. 

Randomized cross stranding 

Capacitance unbalance has a predominant 

effect on the value of the crosstalk, 

particularly at low frequencies. If 

we consider a conventional, concentric 

10 or 25-pair group, fig. 2, it is well 

known that unbalances arise mainly between 

adjacent pairs, 1—2, 2 — 3, 3 — 4 

etc. Unbalances also occur to some extent 

between the center pairs and the 

pairs in the first layer, sometimes also 

between pairs in neighbouring layers. 

Unbalances between any other com 

binations are almost non-existent. It has 

also been established that at least the 

highest unbalances increase approximately 

in direct proportion to the length 

of the cable. 

In cross-stranded cables the random 

mixing ensures that two pairs are adjacent 

only for a limited part of the cable 

length and thus the high capacitance 

unbalance values are reduced. 

The ten pairs in a 10-pair group (fig. 2) 

occupy ten different positions. If, for 

example, we consider pair no. 1, wefind 

that two other pairs can be considered 

as adjacent. Two other positions (in the 

centre of the group) are slightly further 

away but can still be considered as 

adjacent. If the positions of the pairs in 

the group are changed at random along 

the length of cable, we find that two 

arbitrarily chosen pairs will be adjacent 

for only about 4/9 of the cable length. 

The capacitance unbalances contribute 

to the crosstalk mainly during this minor 

part of the cable length. 

Cross stranding of groups that contain 

more than ten pairs gives an even greater 

reduction of the unbalances. In a 

cross-stranded 25-pair group two pairs 

are adjacent for only 3/24 to 4/24 of the 

total cable length, which gives a corresponding 

reduction of the unbalances. 

This calculated reduction is 

approximate, but the tendency is that a 

random mixing of an increasing number 

of pairs gives a corresponding 

reduction of the capacity unbalances

Fig. 4 

Cross stranding device for a 10-pair line 

Fig. 5 

Random pulse generator 

Fig. 6 

between the pairs. For example, in a 

100-pair group the unbalances would 

hardly reach measurable values. 

On the other hand the 10-pair group 

must be considered as the smallest unit 

for which cross stranding gives a 

reasonable reduction of the unbalances. 

For practical reasons, such as 

colour coding, the cross stranding 

technique is considered suitable for 

groups with between 10 and 30 pairs. 

Cross stranding, both randomized and 

systematic, gives the group a certain 

mechanical flexibility. Thus in this respect 

it can be compared with such processes 

as the braiding operation used 

when making flexible cables. 

The most suitable mixing ratio for cross 

stranded 10-pair groups is approximately 

two crossings per metre, and 

these crossings have proved to make 

the cable core looser. This results in 

greater separation of the pairs and thus 

a lower mutual capacitance compared 

with the conditions prevailing in a layer 

stranded cable. When changing over to 

cross-stranded cable the insulation 

thickness can therefore be reduced, for 

the same value of capacitance, which 

means a reduction in cost. This will be 

illustrated later on in the article. 

Process and machines 

107 

The most common pair cable specifications 

prescribe groups containing between 

10 and 25 pairs. Small fixed 

groups are used when the cross stranding 

technique is applied. It is then possible 

to carry out pair twinning and 

stranding of groups in one and the same 

operation. 

A cross stranding line, fig. 3, consists of 

the following main components: 

1. group twinner 

2. random pulse generator 

3. mixer, the cross stranding device 

4. binding head 

5. length measuring device 

6. take-up stand 

Group twinner 

The group twinner is basically a number 

of twinning machines assembled to 

form a unit, fig. 6. The design of the 

twinning machines has intentionally 

been kept uncomplicated. The reason 

for this is that the process is duplicated 

10, 12, 13 or 25 times in each machine. 

There is greater risk of faults in sophisticated 

machines and the efficiency is 

reduced because of the greater number 

of repairs.

108 

Fig. 9 

Take-up stand lor connection wire 

Fig. 7 

Binding head and length measuring device 

Fig. 8, right 

Take-up stands for 10-pair groups 

Random pulse generator 

The random pulse generator, fig. 5, 

utilizes the white noise in a transistor to 

generate randomly distributed pulses 

for the mixer. 

Mixer, cross stranding device 

Fig. 4 shows the cross stranding of a 

10-pair group. The pairs are taken 

through dies which move sideways in 

the cross stranding device. The movements 

of the dies —the mixing of the 

pairs —are controlled by a motor that is 

started and stopped by pulses from the 

random pulse generator. The pairs are 

fanned out over rollers, after which they 

are assembled and bunched together. 

There is no systematic order between 

the pairs because their positions on the 

rollers are changed at random. 

Binding head 

The purpose of the binding head is to fix 

the pairs in the same order that they 

have when leaving the mixer, fig. 7. The 

binding yarn can be used for identification 

purposes. A binding head usually 

has an electromechanical binder yarn 

break detector. The mechanical part of 

the detector has a sensing finger which 

is easily broken, thereby causing the 

machine to stop. The break detector in 

the cross stranding line binding head 

has therefore been redesigned and is 

fully electronic. The binder yarn tension 

can be adjusted during operation. 

Length measuring device 

Fig. 7 also shows the length measuring 

device, including the tachometer which 

synchronizes all drive motors of the 

whole line. 

Take-up stand 

Any type of take-up stand can be used 

for 10-pair groups. Fig. 8 shows a type of 

take-up stand where all drive equipment 

is placed on a frame above the drum 

which leaves the floor free for the transportation 

of drums. A drum twist takeup 

is recommended for 25-pair groups. 

Final assembling 

A conventional stranding machine with 

a drum twist take-up can be used for the 

final assembly. It need only be equipped 

with a few stands for pay-off reels and 

can thus be simple. No back-twist of the 

individual groups is required. 

Supplementary equipment 

Fig. 3 shows an ordinary cross stranding 

line. Accessories for various 

purposes can be included in the line, 

such as taping heads for different taping 

materials. 

If the group twinner is supplemented 

with a specially designed pay-off and 

take-up device it will be suitable for 

simultaneous twinning and coiling of 

connecting wire on small bobbins. Ten

Fig. 10 

Distribution curves, showing the capacitance unbalance 

of 10-pair groups 

Insulation: Solid polyethylene 

Conductor diameter: 0.5 mm 

Cable length: 500 m 

Curve A represents approximately 1000 capacitance unbalance 

values within 10-pair groups in cross stranded 

cables manufactured In the Plteä plant during 1976. 

Curve B represents approximately 1000 capacitance unbalance 

values within concentric (2 + 8) 10-pair groups. 

The shaded area shows the reduction of high capacitance 

unbalance values obtained by introducing the cross 

stranding technique. The expected reduction for other 

curves B (due to the techniques used tor the wire drawing, 

twinning etc.) can be calculated approximately by shifting 

the shaded area 

Fig. 11, right 

Distribution curves, showing capacitance unbalance 

between and within 10-pair groups 




Curve A represents the capacitance unbalance between 

10-pair groups In cross stranded cables 

Curve B represents the capacitance unbalance within 10pair 

groups in cross stranded cables 

bobbins with pairs and triples or five 

bobbins with quadruples and quintuples 

can be manufactured in one operation. 

The take-up device is shown in fig. 

9. 

Cross stranding line 

It has already been stated that since the 

group twinner consists of several individual 

twinning machines, special care 

was devoted to making the design reliable 

and simple. Thus the 10-pair group 

twinner has twenty pay-off shafts, each 

with its own brake. The risk of a 

breakdown because of a brake fault is 

then multiplied by twenty and hence the 

group twinner is equipped with reliable, 

simple rope-brakes. 

Size of reels 

It is generally considered that large 

pay-off reels give high efficiency, but 

experience shows that there is an 

optimum size. Too large reels give rise 

to such disadvantages as conductor 

elongation, long acceleration and retardation 

times etc. 

Most factories in which the introduction 

of cross stranding lines is contemplated 

are already provided with pay-off and 

take-up drums. It must therefore be 

possible to adapt the cross stranding 

equipment for use with a wide range of 

such drums. 

Space requirements 

A cross stranding line requires less floor 

space than conventional equipments, 

109 

owing to the fact that the pair twinning 

and group stranding is carried out in a 

single operation. The group twinner 

alone requires much less space than the 

corresponding number of single twinners 

even if these are of the high-speed 

type. 

Operation 

In the group twinner all twinning heads 

are idle during reloading. This factor 

has a negative effect on the efficiency 

compared with production using the 

corresponding number of single twinning 

machines. A loading table for 

pay-off reels has therefore been included 

in the cross stranding line in order 

to reduce the loading time. A 10-pair 

line has to be reloaded every third to 

fourth hour and the reloading time is 

only ten minutes. Owing to the compactness 

of the line and the smooth operation 

one operator is sufficient for the 

supervision of three 10-pair lines. However, 

it is desirable that two operators 

work together when reloading. 

Electrical characteristics 

of cross stranded cables 

Capacitance unbalance 

The cross stranding technique reduces 

the high unbalance values between the 

pairs and the crosstalk characteristics 

are improved to a corresponding degree 

since no pair combinations are 

permitted to be systematically adjacent 

during any large part of the cable 

length. This is shown in fig. 10.

Insulation: Solid 

polyethylene 



Insulation: Foamed 

polyethylene 



Insulation: Solid 

polyethylene 



Fig. 13 

RMS values of capacitance unbalance distribution 

for cross stranded cable 

Each cross represents the RMS value of the 45 capacitance 

unbalance values within a 10-pair group 

Fig. 12 

Distribution curves, showing the capacitance unbalance 

for 25 and 10-pair groups 




Curve A represents the capacitance unbalance values 

within 25-pair groups In cross stranded cable 

Curve B represents capacitance unbalance values within 

10-pair groups in cross stranded cables 

The characteristics of completed cables 

are naturally also dependent on the 

quality of the individual pairs as regards 

the uniformity of conductors and insulation, 

lay lengths etc. 

As can be seen from fig. 11 the unbalances 

between groups is much less 

than the unbalances within groups. 

Fig. 12 shows that the unbalances in 

25-pair groups are lower than the corresponding 

values in 10-pair groups. 

The quality of a cable as regards capacity 

unbalance is given as the RMS (root 

mean square) value. The distribution 

diagrams in fig. 13 represent the RMS 

values obtained for different types of 

cables. 

As can be seen from the diagrams, the 

spread is relatively large and thus a 

reasonably large number of measured 

values will be required in order to be 

able to establish differences in the quality 

of cables that have been manufactured 

in different ways. 

Mutual capacitance 

In cross stranded cables there is no 

systematic difference in mutual capacitance 

between pairs, caused by their 

positions in different layers. There are, 

however, some small differences in 

mutual capacitance because of the different 

lay lengths and manufacturing 

tolerances of the pairs. This is shown in 

table 1. 

Cross stranded, PE insulated 10-pair 

group cables without jelly filling have a 

lower mutual capacitance than the corresponding 

10-group layer cables 

(2 + 8). The reason for this is that the 

cross stranded cables contain more air 

because of the stranding method. A reduction 

in mutual capacitance of about 

3 % has been noted. 

The mutual capacitance relationships 

are different for cables with other types 

of insulation material. 

The cables are generally specified for a 

fixed mutual capacitance and hence the 

conductor insulation in cross stranded 

cables can be reduced with a consequent 

reduction in material consumption. 

High frequency characteristics 

The high frequency characteristics of 

symmetrical cables are becoming increasingly 

important. This applies 

wherever the cables are situated in the 

network and particularly when they are 

to be used for PCM systems. Typical 

crosstalk values for cross stranded cables, 

given as the mean value m and the 

standard deviations, are shown in table 

2. 

The standard deviation, o, for near-end 

crosstalk is of particular interest. The

PE insulated, solid cable 

10-pair 10-pair 

groups. groups. 

Standard |aid up in cross 

deviation. |ayers stranded 

.1, of the (2 + 8) 

mutual 

capacitance. 

percentage 1.4 0.75 

Table 1 

Near-end crosstalk 25-pair 10-pair 

at 1 MHz groups groups 

m o m o 

dB dB dB dB 

Within groups 63 6 58 6 

Between adjacent 

groups 80 6 68 6 

Between groups separated 

by one group 97 6.6 78 6 

dB dB 

Far-end crosstalk 

at 150 kHz 

RMS 78 70 

Table 2 

Typical crosstalk values for cross stranded cables 

m Mean value 

a Standard deviation 

RMS Root mean square 

Fig. 14 

The number of permissible 30-channel PCM 

systems, N, can be read off from the diagram for 

cr-value for conventional cables with 10 

or 25-pair groups laid up in concentric 

layers is 8 - 10 dB and, as shown in table 

2, the corresponding value for cross 

stranded groups in approximately 6 dB. 

The suitability of a particular cable for 

PCM transmission is dependent on the 

following four parameters: 

m Mean value, crosstalk 

a Standard deviation, crosstalk 

L Attenuation over a repeater section 

N Possible number of PCM systems 

The possible number of 30-channel 

PCM systems can be determined with 

the aid of fig. 14 with a certain degree of 

statistical reliability at given m, L and a 

values. The diagram is based on singlefrequency 

measurements. 

Example 

Two cables with two 10-pair groups 

each, one cross stranded and the other 

with concentric layers, have the following 

typical near-end crosstalk values. 

m = 68 dB 

a = 6 dB for the cross stranded cable 

a = 9 dB for the cable with concentric 

layers 

L = 29dB(m - L =39 dB) 

Fig. 14 shows that the cable with o = 6 

dB can be filled (10 systems) whereas 

the second cable permits only one 

system although the mean value of the 

crosstalk attenuation is the same (68 

dB) for both. As can be seen the lower 

111 

spread of the cross stranded cable is of 

great importance. 

The crosstalk level between 10-pair 

groups in cross stranded cable is 10 dB 

better than the level within groups and 

this ratio is very constant. For groups 

separated by one group there is an additional 

improvement of 10 dB. In the case 

of 25-pair groups the corresponding difference 

is 17 dB. 

These good and well defined values and 

the well organized cable lay-up make 

cross stranded cables very suitable for 

PCM systems. 

Summary 

The method and machines for telecommunication 

manufacture which 

have been described above have resulted 

in 

— improved cable quality 

Owing to the cross stranding of the 

groups the number of high capacitance 

unbalance values between 

pairs is reduced. The capacitance 

level and standard deviation of the 

cable are also reduced. 

- reduced production costs 

Since twinning and group stranding 

are carried out in one single operation, 

the amount of space required is 

reduced and also the investment, 

operation and maintenance costs. In 

addition the planning and supervision 

of the production are simplified.

New Telephone Set 

Arne Boeryd and Gunnar Wiklund 

New standard telephone sets have been introduced on the market at intervals 

of 15-20 years. DIALOG was introduced in 1963 and soon attracted attention and 

appreciation because of its excellent transmission characteristics and high overall 

quality. 

During the second half of 1974 work on developing a new telephone set was started 

in order to meet the demands of the future as regards for example push-button 

dialling and more stable long-distance characteristics. As a result of this work 

LM Ericsson will start production of a new table set, designated DBA 100, during 

the autumn of 1978. 

UDC 621.395.721 

Fig. 1 

Telephone set DBA 100 

Telephone set DBA 100 has been developed 

with the aim of providing a telephone 

set 

— that gives the best possible overall 

economy and which remains up-todate 

for 10-15 years after its introduction 

— which is suitable for both office and 

domestic environments and which 

will meet the demands of the 1980s 

as regards appearance and quality 

— with a simple and reliable construction 

and which lends itself to rational 

production 

— with an entirely modular structure 

that facilitates servicing 

— that is suitable as the basic product 

for a family of telephone sets. 

Work on developing and designing a 

new standard telephone set was started 

jointly by LM Ericsson and the Swedish 

Telecommunications Administration 

during the autumn of 1974, and a development 

assignment was placed with 

ELLEMTEL The work was based on 

jointly prepared specifications and with 

active participation by specialists from 

the Administration and LM Ericsson. 

LM Ericsson's new telephone set, DBA 

100, will be put on the market during 

the autumn of 1978 and will gradually 

replace DIALOG. 

Design 

The requirements that are of prime importance 

for a telephone set relate to 

— the appearance 

— the design of the handset with regard 

to handling and transmission performance 

— the design of the impulsing device 

and its location. 

A number of industrial designers were 

given the task of making suggestions 

for the external design of the set. The 

resultant design models were examined 

from an aesthetical point of view, and 

at the same time the possibilities of rational 

construction were assessed. 

In the design selected, fig. 1, the exterior 

of the set is built up of four units, 

namely the base, rear and front covers 

and the handset. 

Mechanical construction 

When developing the set the possibilities 

provided by the exterior design 

have been exploited in order to limit 

the number of coloured details. This is 

advantageous from the point of view of 

manufacture, stocking sparesand maintenance, 

and at the same time there is 

considerable scope for varying the 

colour of the front cover. 

The base, rear cover and handset are 

manufactured in one colour, preferably 

black. 

The handset has been designed so that 

it rests easily in the hand, reaardless of

ARNE BOERYD 

GUNNAR WIKLUND 

Division for Subscriber Equipments 


Fig. 2 

Exploded view of telephone set DBA 100 

1. Rear cover 

2. Base 

3. Printed board assembly 

4. Front cover 

Fig. 3 

Transmission properties of DBA 100 when using 

whether the user grasps it in the middle 

or at the microphone end. The handset 

also rests on the body of the set in such 

a position that it can easily be picked 

up from any side of the set. 

The set is designed primarily for pushbutton 

dialling. 

One of the basic design aims was to 

create sufficient space in the set for 

printed boards. This means that the necessary 

mechanical components, primarily 

the push-button set and the cradle 

switch, have been designed for 

mounting on the printed board. The 

basic design of the set is shown in fig. 

2. 

A standard set holds one printed board 

assembly that contains the push-button 

set, cradle switch, electronic components 

for impulsing and current feeding, 

and terminals for the handset and 

telephone instrument cords. 

The ringing device used is a conventional 

bell. The base has been equipped 

with the resonators that are required 

for amplifying the sound from the gongs 

within the frequency range 1000-2000 

Hz. 

The construction described here has 

the following advantages from the 

points of view of manufacture, installation 

and maintenance: 

— the front cover is a simple detail without 

any fitting problems or special 

tolerance requirements 

— the set can be tested, packed and 

transported without the front cover. 

The front cover can easily be fitted 

on site, when the customer has chosen 

a colour 

— the weight distribution of the set is 

such that it is easy to carry 

— the number frame is placed on top of 

the rear cover in front of the handset. 

This makes the subscriber number 

easy to read 

— the push-button set is placed on the 

right-hand side of the set, with is 

both convenient and attractive. It is 

placed in an indentation in the cover. 

In this way the set and the printed 

board assembly are protected 

against shocks if the set should fall 

>n to the floor. 

Circuits and components 

113 

All the components are mounted on a 

single printed circuit board. It is therefore 

possible to take full advantage of 

component development and market 

requirements. This can be especially 

worthwhile with regard to pushbutton 

dialling. The design implementation of 

these functional elements meets applicable 

CCITT recommendations, CEPT 

specifications and any additional requirements 

imposed by the telecommunications 

administrations. 

The set will be available either with 

a linear microphone and electronic 

speech circuit or with a carbon microphone 

and a traditional hybrid circuit. 

Identical components will be used as 

receiver and microphone elements in 

the version with an electromagnetic 

microphone. Identical electroacoustic 

components for transmitting and receiving 

are an advantage from the point 

of view of maintenance and stocking 

spares. 

The version with an electret microphone 

provides the maximum quality 

as regards sound reproduction of the 

speech signal. 

The reference attenuation of the set 

relative NOSFER will be the same irrespective 

of whether an electromagnetic 

or electret microphone is used. 

Fig. 3 shows an example of these transmission 

properties when using an electronic 

speech circuit. 

Summary 

LM Ericsson's new telephone set DBA 

100 will be the basic set in a range that 

will cover such applications as: 

— loudspeaking telephone 

— executive-secretary system 

— office telephone systems with a various 

number of exchange lines being 

available to the set. 

This range of telephone sets will be 

introduced successively during 1979.

Digital Line Equipments for 

8 Mbit/s and 2 Mbit/s 

Juho Arras and Örjan Mattsson 

This article presents the digital line equipments included in LM Ericsson's new 

family of PCM systems in the M5 construction practice. PCM multiplex and 

signalling conversion equipment has been described earlier\ The two line equipments 

are intended for transmitting 8.448 Mbit/s and 2.048 Mbit/s over pair and 

quad cables. A unique strapping network has been introduced in the repeater 

equalizers which makes it possible to use existing paper-insulated cables for 

transmitting 8.448 Mbit/s. 

When designing the equipments the latest CCITT and CEPT recommendations 

have been taken into consideration and also the experience gained from the 

earlier generation of 2 Mbit/s line equipment. The equipments are characterized 

by high reliability with generously dimensioned lightning protection, good transmission 

characteristics and a high degree of flexibility in combination with a 

design that makes installation and maintenance easy. The two systems are 

closely related as regards their design. 

UDC 621.395 343 

621.3152: 

621.391.31 

Fig. 1 

Block diagram and interfaces for digital line 

equipment 

MUX PCM multiplex equipment tor 30 circuits 

LTE Line terminating equipment lor a PCM system 

In the terminal station 

Two-way intermediate repeater in a dependent 

repeater station 

D Digital line interface 75 Q 

S Line Interface 

RS Repeater section 

PFS Power feeding section 

FLS Fault location section for repeaters 

CS Cable section 

1) Interface cable (coax. 75 Q) 

2) Line (pair or quad cable) 

~ ~ Signal path 

System aspects 

The new family of digital line equipments 

in the M5 construction practice 

for transmission over pair and quad 

cables consists of 

- ZAD 8-2, with a bit rate of 8.448 

Mbit/s corresponding to PCM transmission 

of 120 telephony channels 

- ZAD 2-3, with a bit rate of 2.048 

Mbit/s corresponding to PCM transmission 

of 30 telephony channels. 

There are great similarities between the 

two systems as regards design and 

equipment. The article will deal mainly 

with ZAD 8-2. The description of ZAD 

2 — 3 is restricted to the parts that differ 

from the previous generation 2 or are 

common for ZAD 2 - 3 and ZAD 8-2. 

Fig. 1 shows the structure of a digital 

line equipment. The basic principles of 

its function have been described in detail 

earlier 2 . The connection to the line 

is via the internationally standardized 

coaxial D interface. The matching between 

the interface and the cable takes 

place in the bay-mounted line terminating 

equipment. The bipolar line 

signal is regenerated in dependent twoway 

regenerative repeaters placed in re 

peater housings along the cable. Two 

line terminating equipments and the intermediate 

line repeaters form a digital 

line section, which is designed as an 

independent functional block with its 

own power and alarm systems. Fault 

location equipment, which is usually 

common for several digital line sections, 

is normally included so that any 

faulty repeaters can be located. The 

transmission takes place over symmetrical 

pairs, one pair for each direction of 

transmission. The two pairs can be in 

the same cable — single-cable operation 

— or in separate cables —two-cable 

operation. Single-cable operation 

means simpler system design. Twocable 

operation has transmission advantages 

since near-end crosstalk, 

which is often the predominant source 

of interference, is eliminated. 

8 Mbit/s on existing cables 

First-order PCM systems were introduced 

in the telecommunication network 

mainly because of the increase in 

the capacity of existing cables that was 

thereby obtained. Experience has 

shown that these systems have provided 

good technical performance and 

good economy. In the case of second-

JUHO ARRAS 

ÖRJAN MATTSSON 

Transmission Division 


Fig. 2 

Comparison of the attenuation characteristics of 

paper-insulated star quad cable (1.2 mm, 25 

nF/km) and polythene-insulated cable based on 

the assumption that the attenuation of both 

cables at 4.224 MHz is 60 dB. The frequency 

dependence of the paper-insulated cable corresponds 

to \ 7+0.6 f and that of the polytheneinsulated 

cable to \ T. 

^"" Paper-insulated 

^ Polythene-insulated 

Fig. 3 

a) Overvoltage protection for the ZAD 2 — 3 line 

repeaters 

Longitudinal overvoltages build up a voltage across R1 

and T so that the gas tube G strikes. During this process 

the repeater equipment and feeding diode D are protected 

by an effective current division between the power 

diode T and R2. 

b) A test pulse used for overvoltage testing. The shortcircuit 

current of the surge voltage generator has been 

varied over the range 200 A to 1300 A. 

order PCM systems it has been assumed 

that special cables with polythene 

insulation will be used. These often 

contain screened groups in order to 

keep the near-end crosstalk at an acceptable 

level with single-cable transmission. 

The 8 Mbit/s system makes 

much greater demands than the 2 

Mbit/s system as regards the separation 

between the transmission directions. 

Considerable financial advantages 

would be attained if existing paper-insulated 

cables could also be used for 

second-order systems. In many cases 

two-cable operation can be arranged or 

a large cable can be utilized so that it is 

possible to achieve the necessary separation. 

As has been mentioned in a previous 

article 3 , at the frequencies of interest 

when transmitting at 8 Mbit/s, paperinsulated 

cables have an attenuation 

curve that deviates from that of polythene-insulated 

cables. There are also 

considerable differences between different 

types of paper-insulated cables. 

The article mentioned above gives the 

theoretical background for the method 

whereby the 8 Mbit/s line repeater can 

be adjusted optimally to suit different 

types of cables, by means of straps in 

the equalizer. ZAD 8 —2 therefore offers 

the attractive possibility of working 

with existing paper-insulated cables 

and also polythene-insulated ones. The 

use of only one type of repeater is advantageous 

from the point of view of maintenance 

and the stocking of spares. 

On the island of Funen in Denmark some 

fifty two-way repeaters have successfully 

been installed and put into operation 

on paper-insulated cable, conductor 

diameter 1.2 mm, capacitance 25 

nF/km. The repeaters work with twocable 

operation, with a repeater spacing 

corresponding to 60 dB attenuation 

at 4.2 MHz. In order to give an idea 

of the difference in the attenuation 

characteristics, the attenuation curves 

of paper and polythene-insulated cables 

are compared in fig. 2. The difference 

in attenuation is as much as ±10 dB 

within the frequency range of the repeater. 

Reliability, overvoltage 

protection, maintenance 

-High reliability is a prerequisite for a 

115 

line equipment. This applies particularly 

for the cascade-coupled line repeaters, 

which are often located in inaccessible 

places. In the design stage great efforts 

have therefore been made to choose 

the most suitable components, and to 

dimension the circuits with ample safety 

margins. In addition the burn-in method 

is used during manufacture in order to 

eliminate unreliable components. 

In rural areas PCM transmission is often 

used in cables where the repeaters 

can be subjected to very severe stress 

in connection with lightning and short 

circuit to earth in nearby power lines. 

Extensive work has been devoted to 

equipping repeaters and other equipment 

with efficient overvoltage protection. 

Fig. 3 shows how such protection 

is arranged in the ZAD 2 — 3 line repeaters. 

The dimensioning, which can cope 

with pulses far in excess of the CCITT 

requirements, has been tested in field 

trials in Norway with both aerial and 

buried cable. 

The repeater protection occupies about 

20% of the area of the printed wiring 

board. The volume of the components 

concerned must be large, among other 

reasons because they have to be able 

to withstand the high powers that arise 

with induced currents of some tens of 

amperes and of long duration. The 

overvoltages are as far as possible 

leaked away via overvoltage tubes before 

they reach the printed board. Exposed 

conductors are made wide, with 

a large distance to adjacent conductors. 

Efficient methods for locating repeater 

and cable faults are essential from 

the point of view of maintenance. A new 

fault locating system for repeaters has 

been developed for ZAD 8 — 2. It is based 

on remotely controlled fault detectors 

in each repeater housing and permits 

measurements during traffic. The line 

terminating equipment includes alarm 

circuits for supervising transmitted and 

received signals and the remote power 

feeding, so that the type of fault can 

easily be determined. The equipment 

at the terminal can be provided with a 

unit that carries out automatic changeover 

to a standby system if a fault 

occurs in the working system.

Fig. 5 

ALBO network for automatic equalization of 

0-25 dB (4.224 MHz) pair cable. The variable 

resistance R is controlled by the peak amplitude 

of the signal after the equalization 

Vf+0.6f 

characteristic 

vT characteristic 

Fig. 6 

Strappable correction network and its frequency 

characteristic 

a) network configuration 

b) attenuation 

The network can be strapped to compensate for all cable 

attenuations of the form Ad=\T+af where (K-a^-0.6 

I.e. the cable parameters 3 can be selected independent 

of each other 

Fig. 4 

Block diagram of the 8 Mbit/s digital repeater 

and the associated signal diagram 

Digital line repeaters for 

ZAD8-2andZAD2-3 

The function and block diagram for the 

repeaters in ZAD 8-2 and ZAD 2-3 

are similar and are shown in fig. 4. 

However, in the case of the 8 Mbit/s 

repeater the detailed design is more 

comprehensive and requires more 

space because of the more complicated 

equalization conditions. Common tasks 

for the two line repeaters are equalization, 

timing recovery and pulse regeneration. 

The purpose of the equalization is to 

compensate for the frequency-dependent 

attenuation introduced by the 

cable. An optimum selection of attenuation/frequency 

characteristic for the 

equalizer means that the effect of disturbance 

is minimized. The line repeaters 

in ZAD 8-2 and ZAD 2-3 were dimensioned 

with the aid of a computer, 

and the goodness criterion was the 

smallest possible signal/noise ratio at 

the repeater input, i.e. maximum number 

of disturbing systems for a given 

bit error rate. For the purpose of dimensioning 

it was assumed that the line 

signal code was one of the internationally 

standardized transmission codes, 

HDB-3orAMI, and that the disturbances 

had crosstalk characteristics. The effect 

of thermal noise has been investigated 

and has been found to have no significance 

for the cable attenuations encountered 

in ZAD 8-2. The maximum 

cable attenuation that can be equalized 

in the repeaters is 65 dB at 4.224 MHz 

for ZAD 8-2 and 35 dB at 1.024 MHz 

for ZAD 2-3. 

The repeaters in the ZAD 8-2 system 

each contain an equalizer consisting of 

the following parts: 

— a fixed part that equalizes the maximum 

attenuation 65 dB of paperinsulated 

pair cable with the attenuation/frequency 

characteristic Vf~+ 

0.6 f. 

— a fixed line building-out (LBO) network 

which simulates a 15 dB cable 

(at 4.224 MHz) and which can be connected 

in for short repeater sections. 

— a variable equalizer (ALBO) network 

for 0-25 dB cable (at 4.224 MHz). 

— a strappable network which can be 

used to adapt the equalization to different 

types of paper and polytheneinsulated 

cable. 

The configuration of the last two of 

these networks are shown in figs. 5 and 

6. This equalizer design means that line 

equipment ZAD 8-2 can be adapted for 

use with all pair and quad cables en-

Fig. 7 

Line repeaters in system ZAD 2-3 (left) and 

ZAD 8-2 (right). The cassettes, with the dimensions 

245X100X45 mm including connectors, 

accommodate one two-way 2 Mbit/s repeater and 

- --L!»/ *~*nAfinnntiunhi 

countered in practice that have an attenuation 

of between 25 dB and 65 dB 

at 4.224 MHz. 

The digital line repeater for ZAD 2-3 

contains an equalizer of the same general 

design as that described above, but 

simpler. In this case there is no need to 

adapt the equalizer for different types 

of cables, since the attenuation/frequency 

characteristic of pair cables is 

affected only slightly by material parameters 

at frequencies less than 1 MHz. 

The timing recovery is carried out by 

filtering the line signal in a resonant 

circuit (Q~80) followed by extraction of 

the zero transitions of the sinusoidal 

signal. The circuit design is such that 

codes with very low pulse density can 

be transmitted, at the same time that 

considerable deviations from the nominal 

bit rate can be tolerated on the lines. 

The reconstruction of the received 

pulse train takes place in two decision 

circuits, which then control the transmission 

of a new regenerated pulse. 

The sequence is illustrated in fig. 4. 

In both systems the power feeding of 

the repeaters takes place with constant 

current over the signal transmitting 

wires. The feeding voltage for the ZAD 

117 

2-3 repeaters has been reduced in relation 

to that used for the repeaters of 

the previous generation. However, attention 

has been paid to the requirement 

that the repeaters must be reliable 

over a large range of temperatures 

(-40"C to + 70°C). 

The mechanical construction of the line 

repeaters is shown in fig. 7. As can be 

seen, a two-way repeater in system ZAD 

2 — 3 is fitted in the same size of cassette 

as a one-way line repeater in ZAD 8 — 2. 

The latter repeater makes great demands 

as regards internal crosstalk because 

of the great differences in levels 

and the mixing of analog and digital 

functions on the same printed board 

assembly. Possible crosstalk paths 

have been eliminated by means of a 

carefully designed layout and the use 

of screening. 

Line terminating equipment 

The main tasks of the line terminating 

equipment are 

- to adapt the signal in the send and 

receive direction between the digital 

link interface D and the symmetrical 

line interface S 

- to power feed the dependent repeaters 

via the cable 

- to detect and indicate alarm conditions.

Fig. 8 

Block diagram of the line terminating equipment 

inZAD8-2 

Electronic switch 

Resonant circuit 

Pulse regenerating circuit 

Strapping field 

Transformer 

Line bullding-out network 

DC-DC converter 

Signal path 

Fig. 9 

Alarm functions in the line terminating equipment 

Absence of pulses, send direction 

Remote power feeding fault 

Absence of pulses, receive direction 

High error rate, receive direction 

Strappable combinatory logic 

Transmission path 

Fig. 8 shows the block diagram for the 

line terminating equipment in system 

ZAD 8-2. In the send direction the bipolar 

signal is converted from unbalanced 

to balanced form in the send 

transformer of the transformer unit. In 

the receive direction the signal is regenerated 

in the terminal repeater, 

which is identical to a one-way dependent 

repeater. If the repeater section 

is short, LBO networks with an attenuation 

of 30 dB at 4.224 MHz are 

connected in. 

The description above also applies for 

ZAD 2-3. In this case no LBO network 

is required, but a 6 dB flat attenuator 

can be strapped in the send direction, 

for example to reduce the cable crosstalk. 

Leaving out the LBO network has 

made it possible to incorporate the 

alarm circuit in the transformer unit. 

Remote power feeding 

The dependent repeaters along the line 

are power fed in series over the phantom 

circuit from the remote power feeding 

unit in the line terminating equipment. 

The same type of unit is used in 

both ZAD 8-2 and ZAD 2-3. The 

power feeding takes place at a constant 

direct current of 48 mA and a voltage of 

up to ±106 V balanced to earth. The 

distance between power feeding stations 

varies from about 20 to 40 km in 

the case of 8 Mbit/s and from about 40 

to 60 km for 2 Mbit/s, depending on the 

repeater spacing and the voltage drop 

in the cable. This distance can almost 

be doubled by using extended feeding 

via separate pairs or by series connection 

of power feeding units. In order to 

ensure personal safety it is possible, by 

strapping, to limit the maximum output 

voltage to approximately 10 V if a break 

should occur in the powerfeeding loop, 

for example a cable break. 

Alarm, automatic changeover 

The line terminating equipments in ZAD 

8-2 and ZAD 2-3 have the same alarm 

functions, fig. 9. Plug-in U-links are 

used to set up the desired connections 

between primary and derived alarms. 

The alarm state of the system is indicated 

by light-emitting diodes, which can 

be seen through the front plate of the 

unit. 

The line terminating equipment can be 

provided with an auxiliary unit which, 

in the case of an alarm in the receive direction, 

provides automatic changeover 

to another, predetermined system that 

serves as a standby, fig. 10. The automatic 

changeover, which is tied to 

single-cable working, is particularly attractive 

if the standby system goes via 

another cable or a radio relay link.

Fig. 10 

Automatic changeover between two systems that 

operate as the working and standby system 

respectively. The changeover is initiated by the 

absence of a signal in the receive direction or too 

high an error rate on the received signal 

Line terminating equipment, system 1 

Two-way dependent repeater 

Control logic 

Fig. 11 

Line terminating shelves for ZAD 8-2 (top) and 

ZAD 2-3. The top shelf is equipped with two 

8 Mbit/s line terminating equipments, the bottom 

shelf with four 2 Mbit/s line terminating equip- 

Mechanical construction 

The line terminating equipments are 

placed in M5 single shelves", fig. 11. A 

shelf holds four systems in ZAD 2-3 

and two systems in ZAD 8-2. The same 

type of shelf is used for both single and 

two-cable operation and for different 

power feeding alternatives. In the 8 

Mbit/s system, with its stringent demands 

as regards crosstalk between 

different parts, a one-way dependent repeater 

is used as the terminal repeater, 

which has been made possible by adapting 

the shelf. 

The interface connections are assembled 

at the left end of the shelf. Eight 

easily accessible coaxial contacts, the 

D interface, are mounted on the inside 

and outside of the left side member. The 

first contact position at the left end of 

the shelf is reserved for the L interface. 

This is used for connecting the line terminating 

shelf to the fault location 

equipment in the bay and for connect 

ing in the system alarm. The interface 

cables are placed in the left bay side 

member. The station cable is brought 

in to the following contact positions in 

the shelf via connection units. 

As regards the bay construction reference 

should be made to the description 

of the 30 channel PCM terminal 

equipment 1 and the M5 construction 

practice 4 . 

The flexible bay design permits mixed 

equipping of 2 and 8 Mbit/s line equipments, 

PCM multiplex, digital multiplexors 

and signalling equipments. 

When the bay is equipped with only line 

equipment it holds, apart from fault location 

equipment, 64 line terminating 

equipments type ZAD 2 — 3 or 36 

line terminating equipments type ZAD 

8-2. The line equipment is fed direct 

from the station battery -24 to -60 V. 

The alarm circuits are fed from —12 V.

Fig. 13 

Small repeater housing of the loading coil box 

type for one 2 Mbit/s system plus fault location 

and speaker circuit equipment. Alternatively 

the housing can be equipped with two 2 Mbit/s 

two-way repeaters 

Fig. 12 

A repeater housing equipped with eight 2 Mbit/s 

two-way repeaters and equipment for fault location 

and speaker circuit. Alternatively the housing 

can be equipped with eight 8 Mbit/s one-way 

repeaters. The housing can also be used to 

accommodate combinations of these repeaters 

Housing for intermediate 

repeaters 

The development of ZAD 8-2 and 

ZAD 2 — 3 has also meant a new generation 

of repeater housings. This work 

has taken place in close collaboration 

between the Nordic Telecommunications 

Administrations and installation 

staff from LM Ericsson. The following 

types of housings are available. 

— Two rectangular housings with capacities 

of 23 and 8 2 Mbit/s two-way 

repeaters or 23 and 8 8 Mbit/s oneway 

repeaters in addition to equipment 

for fault location and a speaker 

circuit. The housings are made of 

steel and silumin respectively and 

are identical to those of the previous 

system generation. The compact 

external dimensions make these 

housings particularly suitable for installation 

in manholes and on poles, 

but they can also be buried. Fig. 12 

shows the smaller of the two housings. 

— A cylindrical steel housing with the 

same fittings and capacity as the 

small rectangular housing. The housing 

is identical with the one used in 

FDM line equipment and is particularly 

suitable for direct burial in the 

ground. 

- A small cylindrical housing made of 

stainless steel. The housing is in principle 

a loading coil box which can be 

opened, fig. 13. It is intended only for 

2 Mbit/s and has a capacity of two 

systems or alternately one system 

plus fault location and speaker 

circuit equipment. The housing is 

intended mainly for easily accessible 

places, for example on poles or in 

manholes, and constitutes a financially 

attractive solution in, for example, 

sparsely populated areas. 

As has already been mentioned, the 

first three types of housings can be 

used for both ZAD 8-2 and ZAD 2-3. 

The accommodation not used can be 

equipped with loading and phantom 

coil units. In general the housings have 

great flexibility as regards equipping 

Movable dividing walls permit varying 

unit dimensions and the connection to 

the stub cable is via plug-in unit connection 

cables, fig. 14. Strapping for 

the power feeding alternative is done in 

these cables in orderto simplify installation 

and change of repeaters. The stub 

cables are made up of screened cable 

units in order to obtain the required separation 

between the transmission directions 

for 8 Mbit/s. 

The repeater housings, which are pressure-tight 

towards the cable and the en-

Unit 

connection 

cable 

Connection 

strip 

Fig. 14 

Unit connection cables are used for connecting 

the units to the stub cable. This arrangement 

gives great flexibility and simple conversion 

between different equipment alternatives 

Fig. 15 

Block diagram of the fault location system 

with remotely controlled bipolar error detectors 

Transformer unit 

One-way repeater 

Electronic switch 

(built Into the one-way repeater) 

Address generator 

Error analyzer 

Address counter 

2 Mbit/s two-way 

repeater 

8 Mbit/s one-way 

repeater 

8 Mbit/s one-way 

repeater 

Filter and 

service unit 

Fault detector 

and service unit 

Side circuit 

loading coil unit 

Phantom circuit 


Phantom circuit 


Measuring box 

Through-connection 

block 

Loop connection 

adapter 

vironment, can be pressurized via the 

stub cable by means of a pneumatic 

resistance or an external valve. The lid 

is sealed with a toroidal ring seal, which 

has proved to be very efficient. 

Location of repeater 

and cable faults 

Fault location equipment ZAD 8 — 2 

A new fault location system for repeaters 

has been devised in connection 

with the development of ZAD 8-2. It 

has a number of advantages compared 

with other systems, such as 

— well defined fault criterion in the 

form of error rate 

— the fact that measurements can be 

carried out during operation, i.e. that 

preventive maintenance is permitted 

— fault location from one supervising 

station 

— identical fault location equipment in 

each housing. 

A characteristic feature of the fault location 

system, fig. 15, is that each inter 

121 

mediate repeater station contains a bipolar 

error detector, which can be used 

to measure the error rate at the output 

of an arbitrary repeater in the housing. 

The supervising terminal station can 

indicate the repeater to be tested via a 

loaded pair, the fault location pair, 

which is common for all intermediate 

repeater stations. The indication is carried 

out by sending a pulse train that 

contains housing and repeater addresses. 

The same fault location pair is used 

for sending the error detector result 

back to the supervising station. The 

communication over the fault location 

pair takes place via data modems 

of the FM type. A transmission speed of 

750 error pulses/s has been chosen as 

giving a suitable compromise between 

information speed, modem complexity 

and demands on the transmission medium. 

It corresponds to a maximum 

transmitted error rate of approximately 

10" 4 . Addressing takes place at the low 

speed of 100 bauds in order to ensure 

that the addressing is reliable. The 

range is limited by the power fed out

122 

Fig. 16 

Fault detector shelf and fault detector and service 

unit. The instrument units are placed to the 

left in the shelf 

and the attenuation of the fault location 

pair. A maximum of 32 housings can be 

connected, on condition that the attenuation 

is less than 40 dB. The power 

feeding is carried out from the supervising 

station using parallel feeding. This 

permits branching of the fault location 

pair. 

The fault location equipment in the repeater 

housing consists of the fault detector 

and service unit, which also contains 

the speaker circuit equipment. All 

housings are equipped with identical 

units and the address identity is determined 

by means of straps. 

At the terminal the fault location equipment 

is assembled in a fault detector 

shelf of the M5 single shelf type, fig. 16. 

The shelf can accommodate the abovementioned 

unit for supervising the terminal 

repeaters in the bay. In the supervising 

terminal the shelf is also equipped 

with the instrument units, including 

power equipment, required for the fault 

location. The received error rate is indicated 

by a light-emitting diode strip. 

The error pulses are also available on a 

counter and a recorder output. The 

housing and repeater addresses are set 

up with thumb-wheel switches. Each 

fault detector shelf can terminate and 

monitor six fault location pairs. 

The unit is prepared for control from an 

external computer which makes possible 

automatic supervision. 

Fault location equipment ZAD 2 — 3 

The fault location method with filter 2 

used in the previous system generation 

has been retained in the 2 Mbit/s equipment. 

A mechanical adaptation to the 

new system has been carried out. In the 

intermediate repeater stations the fault 

location filter has been combined with 

the speaker circuit unit, and this unit 

can also be placed in the terminal in a 

fault location shelf. The fault location 

shelf, a M5 single shelf, can accommodate 

two fault localisation filters, 

and terminate up to six fault location 

pairs. The shelf can also accommodate 

one line terminating equipment, a facility 

that has been provided to cater for 

small stations where there is only one 

PCM system. 

The reasons for retaining the filter 

method were that it is simple and that 

many administrations have access to 

the required measuring instruments. It 

is, however, possible to adapt ZAD 2-3 

to the fault location system of ZAD 

8-2.

Fig. 17 

The instrument "2 Mbit/s line test set" lor investigating 

whether cables are suitable tor PCM 

transmission. Practical operating conditions can 

be simulated and evaluated with the aid of this 

instrument 

Locating of cable faults in 

ZAD8-2andZAD2-3 

In the case of cable breaks it is possible 

to locate the fault in the cable with the 

aid of the power feeding. The power 

feeding unit is then switched over to 

voltage feeding with reversed polarity. 

A current contribution is obtained from 

each repeater before the break point 

and the faulty repeater section can be 

singled out by measuring the sum current 

at the terminal. If the cable fault 

consists of a short circuit between the 

two pairs in the power feeding loop the 

fault can be located by measuring the 

output voltage. 

Line test sets 

LM Ericsson have developed special 

instruments, line test sets, for 8 Mbit/s 

and 2 Mbit/s digital line systems, 

in order to simplify planning, installation 

and fault tracing. The two instruments 

have the same general structure 

and each consists of a transmitter, receiver 

and accumulator with a charging 

device. Fig. 17 shows the 2 Mbit/s 

line test set, which is now in production. 

The various parts are combined 

into one robust mechanical unit. 

The transmitter can generate bipolar 

pulse trains, one of which is crystal 

controlled. The receiver consists of a 

modified one-way repeater, supple 

123 

mented by a bipolar error detector and 

a counter. The modification makes it 

possible to control the equalizer and 

the position of the decision thresholds 

manually. The transmission quality of 

the cable can be checked with the instruments 

by measuring the error rate, 

cable attenuation and eye opening. The 

last test provides a measure of the efficiency 

of the equalization and of any 

reflections. With the 8 Mbit/s instrument 

it is also possible to check the 

strapping chosen in the equalizer with 

regard to the type of cable. The instruments 

can also be used for crosstalk 

measurements or for checking the effect 

of external disturbances such as 

signalling disturbances. During these 

measurements it is often only the end 

points of the cable that are accessible, 

i.e. no working signal can be applied to 

the receiver. Through a unique property 

of the instruments the result can be 

obtained in the form of an equivalent 

error rate. Alternatively the noise power 

at the decision point can be measured. 

The interpretation then assumes a 

knowledge of its amplitude distribut ion. 

Summary 

When developing the digital pair cable 

systems ZAD 8-2 and ZAD 2-3 experience 

from the previous generation of 

2 Mbit/s line systems has been utilized

124 

References 

1. Lindquist, S. and Widl, W.: 30- 

Channel PCM Terminal Equipment 

in the M5 Construction Practice. 

Ericsson Rev. 53 (1976):1, pp. 

38-49. 

2. Arras, J. and Tarle, H.: PCM Line 

Equipment ZAD 2. Ericsson Rev. 

49(1972):2, pp. 47-55. 

3. Fredricsson, S.: Transmission Properties 

of Paper-Insulated Twin 

Cables at High Frequencies. Ericsson 

Rev. 54 (1977):1, pp. 28-31. 

4. Axelson, K., Harris, P.-O. and Storesund, 

E.: M5 Construction Practice 

for Transmission Equipment. 

Ericsson Rev. 52 (1975):3/4, pp. 

94-105. 

and the possibilities offered by construction 

practice M5, component development 

etc. The two systems have 

much in common. The use of the same 

housing admits common equipping 

and facilitates future conversion. ZAD 

8-2 has several unique characteristics, 

for example the possibility of using 

both polythene and existing paper-insulated 

cables, and a fault location 

Technical data 

Electrical data 

Line signal 

Bit rate/symbol rate 

Code 

Impedance 

Pulse amplitude 

Intermediate repeater 

Equalization range 

Power consumption per oneway 

repeater, max. 

Temperature range 

Power supply 

Primary current source 

Feeding of intermediate 

repeaters 

Nominal regulated current 

Output voltage, max 

Mechanical data 

Terminal repeater station 

Shelf dimensions 

Capacity per line terminating 

shelf 

Bay height 

Capacity per bay 

Intermediate repeater station 

Dimensions hxwxl or hx® 

Weight 

Number of two-way 2 Mbit/s 

repeaters or one-way 8 Mbit/s 

repeaters (incl. fault location 

and speaker circuit 

equipment) 

ZAD2-3 

D1 interface S1 interface 

2.048 Mb/s 2.048 Mbaud 

Bipolar HDB-3 or AMI 

75Q unbal 120L> bal. 

±2.37 V 

+ 3.0 V 

5-35 dBat 1 MHz 

8 2 V/48 mA 

-40°Cto + 70"C 

ZDD 532 

310*280x430 mm 

40 kg 

8 

system that permits measurements during 

operation. Compared with the previous 

generation of 2 Mbit/s line systems 

ZAD 2-3 has lower power consumption 

per repeater, i.e. larger power 

feeding distance, better lightning protection 

and a more advanced alarm system. 

Furthermore the volume of the terminal 

equipment is only half that of the 

previous generation. 

ZAD 8-2 

D2 interface S2 interface 

8.448 Mb/s 8.448 Mbaud 

Bipolar HDB-3 or AMI 

75Q unbal. 150Q bal 

±2.37 V + 3.3 V 

40-65 dB strappable 

25-50 dBat 4.2 MHz 

15.5 V/48 mA 

-40'Cto + 70"C 

Battery 24. 36, 48, 60 V 

Rectifier tor 110, 127, 220 V (45-65 Hz) 

Series feeding via the phantom circuit 

48 mA DC 

±106 V bal. 

122x225-473 mm 

ZAD 2-3: 4 systems 


Max. 2743 mm 



ZDD 533 

700x510 mm 

110 kg 

8 

ZDD 534 

320x480x610 mm 

80 kg 

23 

ZDD 535 

280x195 mm 

10 kg 

1 (2 Mbit/s)

Operation and Maintenance 

Characteristics of AKE 13 

Lars G. Ericsson and Åke Persson 

This article is devoted primarily to a description of the operation and maintenance 

characteristics of AKE 13. The article also gives some examples of operational 

experience, but this will be described in more detail in a later issue of Ericsson 

Review. Certain of the facilities offered by AKE 13 as regards international and 

intercontinental traffic are also touched upon. 

UDC621 395 343 AKE 13 is an SPC system intended for 

medium-sized to very large transit exchanges 

for national as well as international 

and intercontinental traffic. The 

first version of AKE 13, AKE 131 with 

control system APZ 130, was taken 

into service in Rotterdam in 1971 and 

was then the first SPC transit exchange 

in the world and also the first 

Table 1 

AKE 13 exchanges in operation or on order on 

o • k~ 1cl 1077 

Country 

Australia 

Czechoslovakia 

Denmark 

Finland 

Italy 

Mexico 

Holland 

Norway 

Sweden 

England 

Total: 

Exchange 

Sydney (1974) - Broadway 

Sydney - Paddington 

Prag 

Ålborg (1974) 

Arhus (1977) 

Albertslund 

Copenhagen (1974) 

Hillerod 

Odense (1976) 

Slagelse 

Virum 

Helsinki, PLH (1974) 

Helsinki, PLH 

Helsinki, HT(1976) 

Turku (1974) 

Bari (ASST) 

Napoli(SIP) 

Palermo (SIP) (1975) 

Padova(SIP) 

Verona (SIP) 

Salerno (SIP) 

Guadalaiara (1975) 

Mexico D F (1973) 

Monterrey (1975) 

Dordrecht (1976) 

Rotterdam DC (1971) 

Rotterdam INT (1976) 

Bergen 

Drammen 

Oslo (1976) 

Skien 

Stavanger 

Gothenburg, Vrr 

Stockholm, FRE (1974) 

Stockholm, HY(1976) 

London-Thames 

multi-processor exchange 1 . However, 

Rotterdam was not LM Ericsson's first 

SPC exchange. AKE 13 was based on 

experience gained from the combined 

local and transit exchange system AKE 

12, which was put into operation in 

Tumba, outside Stockholm, as early as 

1968 2 . 

The latest version of the system, which 

is designated AKE 132 and which contains 

the new control system APZ 150, 

has been described previously 3,5 . 

As can be seen from table 1, 18 AKE 13 

exchanges have been put into operation 

in eight countries in three continents 

National 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

x 

X 

X 

X 

x 

x 

X 

X 

X 

X 

X 

X 

X 

International 

* 

X 

X 

X 

X 

X 

X 

• 

X 

X 

X 

X 

X 

Multiple-capacity 

in 

operation 

2 400 

9600 

12 000 

20 400 

9 600 

15 000 

4 000 

8 000 

3 600 

8 400 

18 600 

6 000 

3 600 

9600 

3 600 

9600 

2 400 

12 000 

Oil 

order 

3 600 

7 200 

18 000 

9600 

6 000 

7 200 

6 000 

29 400 

8 000 

3 200 

6 000 

6 600 

3 600 

3 600 

4 800 

4 800 

7 200 

1 200 

3 600 

3 600 

2 400 

3 600 

3600 

4 800 

16800 

158 400 174 400 

332 800

LARS G ERICSSON 

AKE PERSSON 



Fig 1 

Block diagram of the hardware. An AKE 13 exchange 

can be equipped with up to 8 data processing 

blocks (DPB) 

Each DPB is synchronously duplicated, i.e. consists of 

two sides, each with a complete processor with stores 

and a transfer unit. Both sides normally work In synchronism, 

which Is continuously monitored. However, only one 

side Is executive. When there Is a discrepancy between 

the sides the faulty unit Is disconnected. The duplication 

can be utilized, for example, when changing programs 

and a further 18 exchanges are on order. 

Thus the further development of the 

system that is continuously being carried 

out is founded on long and extensive 

experience. 

System characteristics 

The telecommunications administrations' 

need of transit exchanges with 

high capacity increases with the expansion 

of the long-distance traffic. Previously 

it has not always been possible to 

satisfy the need for such large exchanges, 

and hitherto it has been a fairly 

common practice to combine a number 

of exchange units, each with a relatively 

low maximum capacity, to form what is, 

from the point of view of the network, 

one common switching point. 

A way of solving these problems that is 

often more economical for the telecommunications 

administrations and 

also technically more suitable, not least 

from the point of view of operation and 

maintenance, is to install a single exchange 

having the required capacity. 

AKE 13, with the following inherent 

properties, is able to satisfy all reasonable 

demands as regards lines and traffic: 

— maximum number of incoming lines, 

30000 

— maximum number of outgoing lines, 

30 000 

— maximum number of switched calls 

per hour for the control system APZ 

150, 750 000 

— maximum traffic capacity of the 

switching network with an internal 

congestion of 0.2 %, 25 000 erlangs 

The switching capacity is among the 

largest in the world. The system also 

meets very stringent demands as regards 

reliability and operating 

characteristics. 

Synchronously duplicated 

multi-processor system 

The AKE 13 control system is built up of 

a suitable number of synchronously duplicated 

data processing blocks (DPB), 

with a maximum of eight blocks. The

Table 2 

Extended AKE 13 exchanges Exchange 

Fig.2 

Helsinki 

Copenhagen 

Mexico City 

Mexico City 

Rotterdam DC 

Rotterdam DC 

Rotterdam INT 

Turku 

Turku 

Ålborg 

Ålborg 

Time 

Jan -77 

Nov -75 

Sept -75 

Sept -76 

Mar -73 

July-74 

May -76 

Feb -75 

April -77 

Aug -74 

Feb -77 

Size of the extension 

4 processors 9 600 multiple pos. 

2 „ 7 200 

2 „ 7 200 

1 „ 3 600 

1 200 

1 ,, 3 600 

1 „ 1 200 

800 

1 600 

3 000 

1 200 

data processing capacity of the system 

can thus be extended in step with the 

increase in the number of lines, fig. 1. 

This means that the central, most complex 

and, for the operation most important 

part of the system need never be 

larger than what is required for handling 

the traffic on the lines connected at the 

time. 

The factor that is most important for the 

reliability is the synchronous duplication 

of the control system. It provides 

— the fastest possible fault detection 

through continuous comparison of 

the function of the duplicated units 

— the possibility of easily separating 

software faults and hardware faults 

— simple and reliable fault localization 

— the minimum loss of traffic handling 

capacity when a fault occurs 

— the possibility of introducing new 

functions without disturbing the 

traffic 

Thanks to the duplication it is possible 

to reload the whole system without disturbing 

the traffic. The two sides in the 

system, A and B, which normally work in 

synchronism, are separated by means 

of a command, fig. 2. Side A is then 

loaded with exchange programs and 

data from a tape unit. Side B continues 

the traffic handling without interruption. 

When the loading is completed, the 

newly loaded side A takes over the traf 

Size of the exchange after 

the extension 

6 processors 15 000 multiple pos. 

6 ,, 20 400 

4 „ 15 000 

5 .. 18 600 

2 „ 6 000 

3 „ 9 600 

2 ,, 3 600 

2 „ 6 400 

2 „ 8 000 

4 „ 8 400 

4 „ 9 600 

fic handling and side B is put in the 

standby state. If any operational disturbance 

should then occur because of 

faults in the newly loaded software, 

there will be an automatic changeover 

to side B and the traffic handling will 

again be carried out by the original 

software. When it has been proved that 

the newly loaded side A works 

satisfactorily, updating of side B is 

ordered and also a return to synchronously 

duplicated operation. The updating 

is carried out by copying the contents 

of the A-side stores. 

This facility, which through separation 

of the system sides enables programsto 

be loaded and verified without interruption 

of the traffic handling, can also be 

used when making major changes in the 

software. 

The possibilities offered by the synchronous 

duplication and multi-processor 

arrangement have been utilized 

in the methods for installation and testing 

of extensions that have been used 

successfully in AKE exchanges already 

in operation, table 2. 

The system can be extended by the 

addition of new data processing blocks 

without it being necessary to change 

the contents of the program stores 

already in service. If the extension does 

not include any new functions it is sufficient 

to make certain minor adjust-

128 

Fig. 3 

Standardization of program packages 

merits in the data stores of the data processing 

blocks in service, in order to 

show the changed configuration of the 

control system. 

When extending an exchange, the additional 

data processing block and 

switching equipment are tested by 

means of special installation test programs, 

which are run in the new processor 

before the new units are connected 

to the data processing blocks that are 

already in service. 

Division into function blocks 

Several of the basic characteristics of 

AKE 13 have been obtained by dividing 

the system into function blocks. The 

blocks contain program sequences with 

functionally associated data and also 

hardware units. The interfaces between 

the various blocks are clearly defined 

and the interworking between blocks is 

carried out with the aid of special signals. 

Experience has shown that this structure 

is essential for the design, maintenance 

and production of such a large 

and complex SPC system as AKE 13. To 

develop clear, lucid and well adapted 

documentation for a large program 

system is generally considered as one of 

the most difficult and resource-demanding 

tasks in the production of 

software. However, thanks to the division 

into blocks it has been possible to 

apply the same product handling and 

documentation rules for the AKE 13 

software as have long been used successfully 

for LM Ericsson's earlier exchange 

systems. This has been 

advantageous both for the operation 

and the maintenance of the AKE 13 

systems. 

Standardized software 

When designing software a natural aim 

is to create software that can be used 

for as many exchanges as possible. 

Standardization means simplified document 

handling and improved program 

quality because of the wider field of 

application. This has a favourable 

effect on both exchange and product 

maintenance. 

Thanks to the division into function 

blocks it has been possible to build up 

an extensive program library over the 

years. As regards the switching system 

this library comprises approximately 

200 blocks with standard functions and 

a further 200 blocks containing market-dependent 

functions. Altogether 

this means a total program volume of 

approximately 700 000 words for the 

switching system. The standard blocks 

cover all signalling systems that have 

been specified by CCITT, including No. 

6, and a comprehensive operation and 

maintenance system for the exchange 

switching system. The operating system 

in APZ 150 is general for all exchanges, 

and it has therefore been possible to 

create a standardized system file forthis 

system that applies for all exchanges, 

both as regards the revision status of 

the blocks and their placing (allocation) 

in the program store. The operating system 

is handled as a superior product 

and its status is marked with a revision 

state indication for the whole operating 

system. The revision state is changed 

when functions are added to the operating 

system. The operating system in 

service can be exchanged for a more 

modern one without the environment, 

i.e. the software in the switching system, 

being affected. 

It is also possible to standardize the 

switching system software in the same 

way. This has been done for several 

administrations. The aim has been to 

create, for each administration, as large 

a share of standard allocated program 

volume as possible. The blocks that are 

uniaue for a particular exchanqe are

Software for/he 

switching system 

(APT) 

Standard products 

36 % 

Software for the 

switching system 

New production 

4 % 

Fig. 4 

Distribution of the software volume between 

standard and new production 

Fig. 5 

then added, fig. 3. Thanks to the block 

structure of the software it has thus 

been possible to create standard allocations, 

despite functional differences between 

different exchanges, a fact which 

has been a considerable help in reducing 

an administration's costs. 

The far-reaching standardization has 

meant that nowadays when LM Ericsson 

deliver an exchange in a new market 

it is only necessary to design on average 

4% of the total amount of software 

to be included in the exchange. 

The remainder can be collected as verified 

standard products from a library, 

fig. 4, without any changes being 

necessary. 

AKE 13 in the international 

network 

When AKE 13 was designed, one of the 

prerequisites was that the system 

should be suitable for the handling of 

international and intercontinental traffic 

with particularly complex demands. 

The large traffic handling capacity, 

adaptability to different signalling sys 

129 

tems and traffic routing requirements 

and the comprehensive maintenance 

functions are examples of characteristics 

that are important for the international 

traffic and which it has been possible 

to realize through the SPC technique. 

Of the 36 AKE 13 exchanges which 

have hitherto been put into operation or 

ordered, no less than 14 are international 

exchanges (table 1). 

System AKE 13 is able to provide all traffic 

facilities that have been agreed internationally, 

and the system is suitable 

for all levels in the international 

hierarchy. Today practically all the international 

signalling systems are in 

operation in AKE 13 exchanges, namely 

R1, R2, CCITT 4, CCITT 5 and CCITT 6. 

Facilities for connecting echo suppressors, 

individual ones or from a common 

group, and for automatically connecting 

in and disconnecting attenuators 

are built into the system. All current 

forms of international accounting are 

catered for. Charging can be carried out 

by means of repeated metering pulses 

or toll ticketing. For example, pulse 

charging can be used for the national 

traffic and toll ticketing for the international 

traffic.

130 

Fig. 6 

The control room in an AKE 132 exchange with 

maintenance panel, magnetic tape units and 

other I/O devices 

International maintenance centre, IMC 

In an international exchange it is naturally 

particularly important that the 

maintenance of the exchange and lines 

can be carried out efficiently and that 

suitable aids are available. CCITT recommend 

that the supervision measurement 

and testing of international 

lines and the associated telephone exchange 

equipment should be carried 

out at an international maintenance 

centre, IMC, in the international exchange. 

IMC comprises the following 

parts: 

ISMC Maintenance centre for the international 

exchange 

ITMC Maintenance centre for the international 

lines 

ISCC Administrative centre for coordination 

of the maintenance of exchange 

and lines. ISCC does not 

require any special equipment 

and will therefore not be discussed 

here. 

ISMC 

ISMC has access to functions for 

— supervising the operation 

— testing devices and localizing faults 

— carrying out traffic recording 

In AKE 13 these functions are built into 

the system and are reached via 

typewriters. The ISMC activities are 

therefore usually carried out in the control 

room of the AKE exchange, fig. 6. 

The AKE system provides ISMC with 

some fifty operation and maintenance 

functions for the switching equipment 

Some of these are: 

— supervision of fuses and control 

circuits 

— supervision of traffic disturbances, 

congestion and blocking. An alarm 

and printout are obtained when a certain 

threshold value is exceeded. The 

system also contains functions for a 

more detailed study of each disturbance 

— automatic and semi-automatic 

supervision of the quality of connections 

and calls through observation 

of randomly selected connections 

— automatic checking that each line 

has at least one call every 24 hours 

— automatic signalling check on outgoing 

lines

Fig. 7 

Test desk for ITMC 

The desk contains, among other things, 

— a level meter 

— a variable oscillator 

— a frequency meter 

— a psophometer 

The desk can be connected to the lines either automatically 

via the switching stages In response to a command 

from the typewriter, or manually, via the U-link racks In 

- tracing of the connection path 

through the exchange for a certain 

connection 

- recording of changes in the state of 

devices in a certain connection 

- circuit tester for code receivers and 

code senders. The testing is initiated 

by a command or automatically from 

the disturbance supervision 

— periodic testing of the speech paths 

through the switching network 

— blocking of lines, devices and links 

by means of commands 

— traffic recording and the collection of 

statistics on line routes, device 

groups and link routes. There is a 

wide range of measurement types 

available in addition to those recommended 

by CCITT. 

ITMC 

Extensive equipment is placed at the 

disposal of ITMC for the maintenance of 

international lines: 

Measuring equipment for making fully 

automatic transmission measurements 

in accordance with CCITT recommendations. 

The measuring equipment is of 

two types. One type is designated ATME 

(Automatic Transmission Measuring 

Equipment) and carries out level and 

noise measurements on international 

131 

lines in accordance with CCITT recommendation 

No. 2. The other type consists 

of automatic test equipments; 

CCITT 12 which uses CCITT measuring 

methods Nos. 1 and 2 for routine checks 

of the transmission quality on international 

lines with signalling in accordance 

with CCITT system No. 4, and 

STC (Simplified Transmission Check) 

for routine checks on international lines 

with signalling in accordance with 

signalling system R2. The measurements 

are controlled by a previously 

stored program that indicates when the 

measurements are to be made and on 

which lines. 

A test desk with instrument for making 

manual or semi-automatic transmission 

measurements, fig. 7. As can be seen 

from fig. 8, these desks can be connected 

both to the station side of the 

junction line relay sets, via the selector 

network, and to the line side, via U-link 

racks (jack racks that give access out 

towards the line or in towards the station). 

U-link racks for connecting lines to the 

test desk. (Certain telecommunications 

administrations, however, consider that 

the U-link racks can be omitted, since a 

junction line relay set in an SPC ex- 

WilH UiUdl/r 

IP ,1

Table 3 

Number of component faults per rack and operating 

year in the Rotterdam DC 

Fig. 8 

Connection of the ITMC test desk to the switching 

network 

Type of equipment 

Central data processing equipment 

Test and control equipment 

I/O equipment 

Code switches 

Other switching devices 

No. of 

racks 

30 

17 

2 

64 

90 

change is small compared with one in a 

conventional exchange because the 

logic functions are carried out by the 

software.) 

Route supervision panel with lamps for 

indicating route congestion and various 

types of blocking. 

A typewriter that provides access to all 

supervisory functions in the system. 

The design of ITMC can vary depending 

on the size of the exchange and the 

number of international lines. The 

equipment is normally placed in a separate 

room. It is then often most convenient 

to put the U-link racks in the same 

room. For small international exchanges, 

the ITMC equipment can be 

placed in the maintenance desk in the 

control room. 

Operational experience 

The SPC technique has made it possible 

to rationalize the operation and maintenance 

work to a very great extent. The 

administrations have pointed out many 

advantages, for example: 

- that changes of traffic routing data, 

route information and also charging 

and accounting data require considerably 

less resources and can be carried 

out in very much shorter time in 

AKE 13 than in conventional systems. 

A comparison is made on the last 

page of this article 

— that it is easier to introduce functional 

changes since the majority of the 

1972 

No. of faults 

per rack 

04 

1 82 

2.0 

0.047 

0.28 

No. of 

racks 

47 

32 

4 

128 

158 

1975 

No. of faults 

per rack 

0.28 

1.53 

0.25 

0056 

0082 

functions are realized in software 

— that the efficient supervision and 

fault localization functions have 

meant that in AKE 13, more often than 

in previous systems, faults are detected 

and cleared before the subscribers 

complain 

— that the connection and testing of 

lines is greatly facilitated by the 

maintenance panel and typewriter 

provided. 

Extension of exchanges in operation 

It has already been mentioned that several 

AKE 13 exchanges in operation 

have been extended, table 2. The great 

flexibility of the system offers an almost 

unlimited variety of extension configurations, 

but experience from the extensions 

that have been carried out 

shows that it is possible to limit and 

standardize the number of extension 

configurations and still meet all requirements 

that the administrations 

may have. This standardization has the 

following advantages: 

— it admits the development of standardized 

methods and aids 

— it gives short installation and testing 

times 

— extensions can be carried out without 

specialist aid 

— it reduces the amount of resources 

required in all handling stages 

— it gives high reliability 

Component reliability 

In a previous article on the first AKE 13 

exchange, Rotterdam DC 1 , the number

Fig. 9 

System restart frequency in the AKE 13 exchange 

in the Rotterdam DC with 3 DPBs and 9 600 

multiple positions 

1. The switching stages and data store were extended at 

the beginning of 1973 

2 The exchange was extended by the inclusion ot a new 

data processing block and new switching stages at the 

beginning ot 1974 

3. An inverter fault occurred in June 1975 

— Mean value tor 4 months 

of component faults per rack was given 

for the various parts of the system during 

the first year of operation, 1972. 

These figures are given in table 3, supplemented 

by the corresponding figures 

for 1975. It should be noted that the 

exchange has been extended in the 

meantime. The table verifies the high 

component reliability, which has proved 

to be very stable and has even improved 

during the time the exchange has been 

in operation. 

System restart 

The system restart is such a basic function 

in the fault clearing operations that 

it deserves a special description. 

A software or handling fault can manifest 

itself in several ways, for example 

through 

— the normal program handling ceasing 

wholly or partly 

— an unauthorized attempt to write 

data in a specially protected area 

— a jump in the software being addressed 

to an unequipped part of the 

store. 

Number of automatic 

restarts per month 

133 

Restart takes place when any of the 

above fault situations occur. 

A hardware fault in a processor side is 

detected by the system maintenance 

unit and can usually be located and isolated 

without affecting the operation. In 

the exceptional cases when this is unsuccessful, 

for example if a double fault 

occurs, restart also takes place. Such a 

restart means that temporary data are 

cleared, whereby any faulty data are removed. 

The system is then set to an initial 

state where it can start handling 

traffic again. 

In the first place a normal system restart 

takes place, in which calls in the register 

state (i.e. connections in the process of 

being set up) are disconnected. This 

takes approximately 30 seconds and 

during this time no new calls can be accepted. 

Calls that have already been 

established are not affected. 

If repeated normal restarts do not have 

the desired effect, or if the number of 

restarts during a short period of time 

exceeds a preset value, a major system 

restart takes place. This means that 

established calls are also disconnected. 

Such restarts are relatively few and are 

carried out in approximately 15 seconds. 

The exchange staff may sometimes 

want to "clean up" the exchange and 

they then carry out a manual restart, 

normal or major. A manual system restart 

is also carried out in connection 

with function changes and when a data 

processing block is put into operation 

or taken out. These manual restarts are 

usually carried out during periods of 

low traffic. 

Subscribers who happen to call the exchange 

during a system restart experi-

134 

ence this as congestion or a "silent 

connection". They then make a new and 

normally successful call attempt, and 

thus the traffic handling disturbances 

must be considered as negligible. 

Fig. 9 shows the system restart rate for 

the very first AKE 13 exchange, Rotterdam 

DC, from when it was first put 

into operation until the end of 1976. The 

great reduction in the number of restarts 

is a result of the successive improvement 

and stabilization of the 

system and also the clearance of faults 

in the exchange itself. A number of 

faults were revealed during the period 

immediately after the system had been 

put into operation, when new programs 

were taken into use and more lines connected 

in. Hence the number of system 

restarts per month increased until 

March 1972, and then started to decrease. 

When a system restart is carried out a 

printout is obtained, stating the type of 

fault. Atthesametime data are recorded 

on magnetic tape that define the system 

statewhen thefaultoccurred. Thisgives 

valuable information for further fault 

tracing. 

In conclusion it can be said that the 

system restart function is an excellent 

aid for maintaining the operational reliability 

of the system, since it limits the 

effects of a fault and also provides the 

basic data for clearing program and 

handling faults. Furthermore the possibility 

of initating a system restart manually 

means that the operating staff 

have been given a tool that enables 

them to clear up a complex fault situation. 

Successive improvements 

The AKE 13 system has been delivered 

to some of the most technically 

advanced administrations in the world. 

In meeting their different requirements 

AKE 13 was successively supplemented, 

so that it now constitutes a 

system that meets the most divergent 

demands, especially as regards operation 

and maintenance. The administrations' 

experience of AKE 13 has also 

provided views that have resulted in 

new facilities and improved handling 

methods. 

As new techniques become available 

the possibility arises of adding new system 

components, which increase the 

capacity of the system, enlarge its field 

of use, improve its operational reliability 

and simplify its handling. Processor 

APZ 150 is one example of this development. 

This modern processor was 

used for the first time in Stockholm 

(Hammarby exchange) in June 1976. 

Three more exchanges with APZ 150 

were taken into service in 1976, in 

Odense (Denmark), Oslo (Norway) and 

Helsinki (Finland). By using integrated 

circuit engineering and semiconductor 

memories it has been possible, for 

example, to reduce the space requirements 

and increase the traffic handling 

capacity. A list of the most important 

improvements that APZ 150 has brought 

the AKE 13 system is given on the opposite 

page. 

Another example of the continuous development 

of the AKE system is the introduction 

of regional computers. Thus 

the LM Ericsson type APN 163 

minicomputers are used in AKE 13 for 

several applications, for example forthe 

signalling terminals in the latest AKE 

generation of the CCITT signalling system 

No. 6, and for the display-based 

operator system ANE 403. Minicomputer 

APN 163, which is also used in several 

applications outside the telecommunications 

field, has been designed with 

special regard paid to the stringent demands 

on reliability that a telephone 

exchange makes. The list of instructions 

for APN 163 has also been designed 

to meet the requirements of SPC 

exchanges. Since the minicomputer 

has been designed by LM Ericsson it 

has been possible to integrate its operation 

and maintenance with that of the 

remainder of the exchange. 

The use of regional computers provides 

valuable flexibility at the interface between 

the central functions in the control 

part of the AKE system and the functions 

of the peripheral units, which are 

often affected by external conditions. In 

certain cases it has also been possible 

to relieve the central control system of 

routine but capacity demanding functions, 

which would otherwise have reduced 

the overall traffic handling 

ranaritu nf tho QvQtpm

Comparison of the amount of work required for installing a new 

route in a conventional exchange and in an AKE 13 exchange 

Assume that a new outgoing line route of 30 lines is to be connected in. The exchange 

has 3 000 incoming and 3 000 outgoing lines. 

In a conventional transit exchange the 

work includes the following work operations: 

I.New number analysis wirings, route 

type markings and wires for idle marking 

must be included in the route marking 

devices. 

2. In the line selection devices the line test 

wires must be strapped to connection 

relays. 

3. Straps must be made in the exchange 

intermediate distribution frames (IDF) 

for connecting the idle marking, test, 

control and statistics wires of the new 

junction line relay sets. 

4. The speech and control wires of the 

junction line relay sets must be connected 

in the IDF to the correct position 

in a selector stage multiple (in AKE 13 

this is normally done by means of fixed 

exchange wiring). 

The work is carried out in different parts 

of the exchange rack room and is concluded 

by deblocking the lines with the 

aid of the deblocking button on each 

junction relay set in the relay set rack in 

question. 

The exchange is assumed to comprise 22 

central route marking devices and 25 line 

selecting devices. 

A total of approximately 740 straps or IDF 

wires must be connected. Assuming that 

the work is carried out by experienced 

staff, a total of approximately 31 work 

hours is required (8 hours of which are 

required for connecting the lines to the 

switching stages). 

APZ 150 compared 

with APZ 130 

- The capacity approx. 3 times larger 

- The amount of space required for 

the control part is reduced to 1/3 

for the same capacity 

- The power required for the control 

part is reduced to 1/3 for the same 

traffic handling capacity 

- The use of integrated circuits instead 

of discrete components increases 

the reliability 

- More efficient fault localization 

system 

- Automatic restart with reloading 

and safeguarding of certain data 

when the system restart function 

cannot restore the exchange to 

traffic handling 

- Improved aids in the system for 

functional changes and changes in 

size 

- Improved facilities for tracing 

program faults 

- Advanced system for safe introduction 

of program changes during 

operation 

In an AKE 13 exchange all operations are 

carried out from the control room with the 

aid of commands, which are either typed 

on a typewriter or punched and read in 

via a punched tape reader 

1. A command that creates the new route 

and gives it the correct characteristics 

5-10 minutes 

2. One command per line to include it in 

the new route 

approximately 30 minutes 

3. Commands for dimensioning supervision 

of congestion, disturbance and 

blocking for the route 10-15 minutes 

4. Changing the digit analysis tables 


Consists of the following operations: 

- punching the analysis command 

- mounting the magnetic tape for the 

change in the analysis table and writing 

the command 

- read-in of the control commands 

- read-in of the analysis commands 

- read-in of the loading tape 

5. One deblocking command per line 


A total of 11/2-2 hours is required, including 

the punching of the command 

tapes. 

References 

1. Hamstad.O. and Norén, L.-O.AKE 

131 Rotterdam Exchange and Experience 

from First Year of Operation. 

Ericsson Rev. 50 (1973):2, pp. 

58-64. 

2. Sundblad, A.: Operating Experience 

from AKE 120, Tumba. Ericsson 

Rev. 47 (1970):2, pp. 42-49. 

3. Meurling, J., Norén, L.-O. and 

Svedberg, B.: Transit Exchange 

System AKE 132. Ericsson Rev. 50 

(1973):2. pp. 34-57. 

4. Norén, L.-O. and Sundström, S.: 

Software System for AKE 13. Ericsson 

Rev. 5? (1974):2, pp. 34-47. 

5. Nilsson, R. and Norén, L.-O.: In- 

Plant System Testing. Ericsson 

Rev. 53 (1976):1, pp. 19-27. 

6. Norén, L.-O. and Sundström, S.: 

Development, Production and 

Maintenance of Software for AKE 

13. Ericsson Rev. 53 (1976):3, pp. 

152-160. 

135

ABJ 101-the Modern Public 

Magneto Switchboard 

Lennart Aldestam 

The demand for manual magneto switchboards has increased considerably during 

recent years. There are large areas where conditions are such that magneto switchboards 

offer a satisfactory and economical solution to the telecommunication 

problems as also long lines of not very high quality can be connected. 

In order to meet this growing demand LM Ericsson, in close cooperation with 

many of their customers, have developed a modern, single-position magneto 

switchboard designated ABJ 101. ABJ 101 can operate either as an independent 

exchange or in combination with an automatic exchange (PAX), AKD 860. 

UDC 621.395 343 

Fig. 1 

ABJ 101 equipped for 40 magneto lines, 4 CB 

junction lines and 10 cord pairs 

1. Base unit 

2. Line shelf 

3. Line unit for magneto lines 

4. Line unit for CB junction lines 

5. Supervision unit 

6. Cord pair unit 

7. Position unit 

ABJ 101 -a compact and 

flexible switchboard 

ABJ 101 is a compact and modern 

magneto switchboard with all equipment 

built into the chassis. The 

switchboard has a modular structure, 

fig. 1, and the units are connected via 

plugs and jacks, which means simple 

and fast installation. 

This construction gives a low initial cost 

and permits extension in stages. No 

special tools are required for assembling 

and installing the switchboard. 

Owing to the fact that the switchboard is 

built up of such components as miniature 

relays and cord winders it has very 

small dimensions and thus requires 

only a third of the volume of space required 

for traditional floor switchboard. 

ABJ 101 can be placed on a desk, counter 

etc. and merges well with different 

surroundings. The small dimensions 

mean that it is usually very easy to find 

a suitable place for the switchboard. 

Can be extended from 10 to 240 lines 

The switchboard can be extended in units 

of ten magneto lines, four CB junction 

lines and one cord pair. 

The final capacity is 18 cord pairs and 

either 240 magneto lines or 220 

magneto lines and 8 CB junction lines, 

fig. 2. Thus the system covers a very 

wide capacity range. The switchboard is 

already wired for full capacity when delivered. 

All apparatus is inserted from 

the front. 

Administrations with several switchboards 

may find it advantageous to 

stock extension equipment themselves. 

The cost of this will be small. 

High operator efficiency 

A summary of the most important 

characteristics of ABJ 101 is given at the 

end of the article. Many of these 

characteristics are such that they enable 

the operator to handle a larger 

amount of traffic and provide better 

service for the subscribers.

LENNARTALDESTAM 



Fig. 2 

ABJ 101 with two line boxes equipped for 130 

magneto lines and 14 cord pairs (maximum 160 

magneto lines with two line boxes). The capacity 

is extended to the final number of 240 magneto 

Some examples of such aids are automatically 

generated ringing (transistorized), 

ring-back tone to the calling 

subscriber and supervision of a junction 

line when other calls are being handled. 

The switchboard can also be equipped 

with a push-button set for decadic impulsing 

when required. Furthermore 

control devices have been positioned 

and the colour scheme selected with the 

aim of making the work of the operator 

as easy and pleasant as possible. 

Independent exchange 

ABJ 101 can be included in a network as 

an independent exchange and then interwork 

with all types of manual and automatic 

public systems. 

Mechanical design 

From the points of view of construction 

and function the switchboard consists 

of two main parts, namely the basic unit 

and line boxes. The basic unit contains 

a central wiring unit to which all wiring 

between different equipment has been 

concentrated. Position and cord pair 

equipment is mounted in the basic unit. 

The line boxes contain magneto line 

and CB junction line units. The first line 

box also contains a supervision unit. 

Incoming lines are connected to the 

137 

equipment in the line boxeseitherdirect 

or via a wall-mounted connection box. 

(Magneto lines are connected via 10pair 

cables and CB junction lines via 4pair 

cables.) 

The sides of the switchboard are made 

of teak in natural colour with a plastic 

finish. The plates for mounting the line 

units and the top and rear plates of the 

exchange are finished in green. The 

cord pair and position units are framed 

by anoidized light metal sections. Vacant 

positions are covered by green plastic 

strips. 

All components meet the requirements 

for good insulation, shape permanence 

etc. even during extreme climatic conditions. 

Cord pair equipment 

The components for a cord pair have 

been made up into a cord pair unit, fig. 

4. 

The unit, the front of which is covered 

with green plastic, contains two cord 

winders with 3-pole cords and plugs. 

The plugs have covers and protective 

spirals made of grey plastic, which together 

with the design of the cord winder 

considerably reduce the mechanical 

stress on the cord.

Fig. 3 

Line unit for 10 magneto lines 

Fig. 4 

Cord pair unit 

AP Answering cord 

RP Calling cord 

SK-RK 3-posltlon switch with speech position SK and 

ringing position RK 

SL Clearing drop indicator 

LM Ericsson have long operational experience 

of cord winders obtained from 

the portable switchboards ABM 10, 

which have withstood severe trials under 

field conditions. The cord winder is 

a corner stone in the ABJ construction 

and has greatly contributed to the reduction 

of the switchboard volume. 

The cord pair unit also includes a 3position 

switch and a clearing drop indicator. 

The switch, which has small 

dimensions, has a frame and lever arm 

made of grey plastic. 

Line equipment 

The line units are available in two variants, 

one for magneto lines, fig. 3, and 

one for CB junction lines. Among other 

things the line units contain a drop indicator 

jack strip. The CB junction line 

units also contain a printed board assembly 

with line components. 

Position equipment 

The dial and other control devices that 

are common for the whole of the exchange 

have been assembled in a position 

unit. The front of the unit is covered 

with a plate of green plastic. 

Supervision equipment 

A flag indicator, battery indicator and 

jacks for checking cords etc. are assembled 

in a supervision unit. 

ABJ 101 in combination with 

automatic exchange AKD 860 

For certain telecommunication requirements 

in rural areas LM Ericsson 

can offer a new, economical system 

consisting of the magneto switchboard 

ABJ 101 in combination with an automatic 

exchange (PAX) AKD 860, fig. 5. 

This system is intended for very small 

communities and can be used while 

waiting for the demand to increase sufficiently 

to justify a changeover to a fully 

automatic rural exchange system. The 

combination of these two standard

Fig. 5 

ABJ 101 in combination with automatic exchange 

AOK 860 gives dialled calls in a the densely populated 

area and manually extended calls in the 

surrounding rural area. Both subscriber categories 

have the possibility of national and international 

calls via the operator in the manual 

switchboard 

products gives subscribers in densely 

populated areas many of the 

advantages of automatic calls and at the 

same time offers remote subscribers in 

the surrounding areas telephone 

service via the modern manual 

switchboard. 

All subscribers have the possibility of 

national and international calls via the 

operator at the manual switchboard. A 

subscriber in AKD 860 calls the operator 

by dialling a single-digit number. Calls 

within AKD 860 are set up automatically 

and within ABJ 101 manually. Calls between 

subscribers in ABJ 101 and AKD 

860 are set up by the operator. 

Exchange AKD 860 is built up of plug-in 

units, which means simple and fast installation 

and low maintenance costs. 

This construction permits extension in 

stages and facilitiates any future move 

of the equipment to another location. 

The small dimensions enable the 

system to be installed in suitable existing 

premises, and thus no special building 

is required. 

The operator at the manual switchboard 

handles the charging for trunk calls and 

in certain cases this is done in cooperation 

with the trunk operator in the 

superior exchange. 

Accessories for ABJ 101 

139 

Power equipment 

For power supply four dry-cell batteries 

BKA 1002 for 1.5 V and 50 Ah are recommended. 

These are placed in battery 

box BKY 1012. 

Main distribution frame 

Main distribution frame NBA is recommended 

for switchboards with more 

than 40 lines. A main distribution frame, 

but without line fuses, can also be 

obtained through using double the 

number of connection boxes. 

Telephone sets 

Ordinary magneto telephone sets are 

connected to the exchange, for example 

LM Ericsson's model DAG 11102/8. 

External bell 

When an acoustic signal is needed outside 

the switchboard, a bell KLD 1303, 

can be connected. Various outdoor 

bells can also be used. 

Wooden sides 

ABJ 101 can be adapted to the environment 

at the installation site. The switchboard 

is delivered with teak sides. Sets 

of side pieces made of jacaranda, 

natural pine, walnut or other types of 

wood can be supplied on special request.

" The maximum number of lines that can be connected 

to a certain switchboard is dependent on a 

number of factors, such as the amount of traffic, 

type of traffic, the efficiency of the operator, calling 

habits, local tradition etc. Under normal circumstances 

an operator in a single-position magneto 

switchboard can handle a maximum of 100-140 

magneto lines and 8 CB lines. However, if the 

amount of traffic is very small it is possible in some 

cases to handle more than 200 lines 

Technical data 

Maximum number* of 

magneto lines 

CB junction lines 

Cord pairs 

Dimensions in cm 

Width 

Height 

Depth 

Approx. weight, kg 

Operating voltage 

6VD.C. 

Base unit 

+ 1 line box 

80 70 60 

- 4 8 

18 18 18 

62 

41 

53 

40 

Line resistance 

The maximum value of the line resistance 

for magneto lines is dependent on 

the line attenuation, which may amount 

to 15 dB. The leakage resistance must 

not be less than 10000 ohms. The indicators 

drop at 9 mA. The resistance and 

leakage values for CB junction lines are 

primarily dependent on the limit values 

of the main exchange. Thus the maximum 

values for these lines must be 

calculated on the basis of data from the 

main exchange. 

Base unit 

+ 2 line boxes 

160 150 140 

- 4 8 

18 18 18 

ABJ 101 

62 

59 

53 

55 

Base unit 

+ 3 line boxes 

240 230 220 

4 8 

18 18 18 

62 

77 

53 

70 

Advantages 

The exchange has been given all the 

characteristics that can be demanded 

from a modern manual magneto 

switchboard which means that 

— CB junction lines from manual or automatic 

exchanges can be connected 

— magneto junction lines can be connected 

to the ordinary magneto units 

— supervision of a junction line can be 

carried out by the operator while 

handling other calls 

— line splitting gives the operator the 

possibility of talking to one party 

without the other being able to overhear 

the conversation 

— the ringing is generated automatically 

(transistorized) 

— a flag indicator indicates that a signal 

is being sent out 

— a ring-back tone is sent to the caller 

— backward ringing can be carried out 

via the answering cord 

— acoustic signals can be obtained 

concurrently with incoming seizure 

and clear-forward signals 

— a fixed acoustic signal can be connected 

in by means of a switch 

— dropped indicators are automatically 

reset during the handling of the calls 

— a battery indicator indicates when it 

is time to check the condition of the 

battery 

— testing of the cords can be performed 

— an automatic fuse eliminates fuse 

changes 

— anextrajack is provided for connecting 

in a handset for an assistance 

operator 

— space is provided forthe memoranda 

that the operator needs to have readily 

accessible in order to be able to 

work rapidly and efficiently.

The Ericsson Group 

With associated companies and representatives 

EUROPE 

SWEDEN 

Stockholm 

1. Teletonaktiebolaget LM Ericsson 

2. LM Ericsson Telematenel AB 

1. ABRrfa 

1. Sieverts Kabelverk AB 

5. ELLEMTEL Utvecklings AB 

1. AB Transvertex 

4. Svenska Elgrossist AB SELGA 

1. Kabmatik AB 

4. Holm & Ericsons Elektriska A8 

4. Mellansvenska Elektriska AB 

4. SELGA Mellansverige AB 

Alingsås 

3. Kabeldon AB 

Gävle 

2. Vanadts Entreprenad AB 

Gothenburg 

4. SELGA Västsverige AB 

Kungsbacka 

3. Bota Kabel AB 

Malmö 

3. Bjurhagens Fabrikers AB 

4. SELGA Sydsverige AB 

Norrköping 

3. AB Norrköpings Kabelfabrik 

4. SELGA östsverige AB 

Nyköping 

1. Thorsman & Co AB 

Spånga 

1. Svenska Radio AB 

Sundsvall 

4. SELGA Norrland AB 

Växjö 

1. Widells Metallprodukter AB 

EUROPE (excluding 

Sweden) 

DENMARK 

Copenhagen 

2. LM Ericsson A/S 

1. Dansk Signal Industri A/S 

3. GNT AUTOMATIC A/S 

1. I. Bager&Co A/S 

Tfistrup 

2. Thorsman & Co Aps 

2. LM Ericsson Radio Aps 

FINLAND 

Helsinki 

2. Oy Thorsman & Co Ab 

Jorvas 

1. Oy LM Ericsson Ab 

FRANCE 

Colombes 

3. Société Francaise des 

Telephones Ericsson 

Paris 

2. ThorsmansS.a.r.l. 

Bologne sur Mer 

1. RIFAS.A. 

Marseille 

4. Etablissements Ferrer-Auran S.A. 

IRELAND 

Athlone 

1. LM Ericsson Ltd. 

Drogheda 

2. Thorsman Ireland Ltd. 

ITALY 

Rome 

1. FATMESoc. per Az 

5. SETEMERSoc per Az. 

2. SIELTESoc. perAz 

The NETHERLANDS 

Rijen 

1. Ericsson Telefoonmaatschappij B.V. 

NORWAY 

Nesbru 

Oslo 

2. SRA Radio A/S 

4. A/S Telesystemer 

4. A/S Installatör 

Drammen 

3. A/S Norsk Kabelfabrik 

POLAND 

Warszaw 

7. Telefonaktiebolaget LM Ericsson 

PORTUGAL 

Lisbon 

2. Sociedade Ericsson de Portugal Lda 

SPAIN 

Madrid 

1. Irtdustrias de Telecommunicact6n S.A. 

(Intelsa) 

1. LM Ericsson S.A. 

SWITZERLAND 

Zurich 

2. Ericsson AG 

UNITED KINGDOM 

Horsham 

4. Thorn-Ericsson Telecommunications 

(Sales) Ltd 

2. Swedish Ericsson Rentals Ltd. 

5. Swedish Encsson Company Ltd. 

3. Thorn-Ericsson Telecommunications 

(Mfg) Ltd. 

London 

6. Thorn-Encsson Telecommunications 

Ltd 

4. United Marine Leasing Ltd. 

4. United Marine Electronics {UK) Ltd 

WEST GERMANY 

Frankfurt-am-Maln 

2. Rifa GmbH 

Hamburg 

4. UME Marine Nachnchtentechnik, GmbH 

Hanover 

2. Ericsson Centrum GmbH 

Ludenschetd'Ptepersloh 

2. Thorsman & Co GmbH 

Representatives In: 

Austria, Belgium, Greece, Iceland, Luxembourg. 

Yugoslavia. 

LATIN AMERICA 

ARGENTINA 

Buenos Aires 

1. Cia Ericsson S.A C.I. 

1. Industrias Eléctricas de Quilmes S.A. 

5. Cia Argentina de Teléfonos S.A 

5. Cia Entrernana de Telétonos S.A. 

BRAZIL 

Säo Paulo 

1. Ericsson do Brasil Comércio e 

Industria S.A. 

4. Sielte SA. Instalacöes Elétricas e 

Telefönicas 

4. TELEPLAN, Projetos e Planejamentos 

de Telecommunicates S A 

Rio de Janeiro 

3. Fios e Cabos Plåsticos do 

Brasil S.A 

Säo José dos Campos 

1. Telecomponentes Comércio e 

Industria S.A. 

CHILE 

Santiago 

2. Cla Ericsson de Chile S.A. 

COLOMBIA 

Bogota 

1. Ericsson de Colombia S.A. 

Call 

1. Fåbricas Colombianas de Materiales 

Eléctricos Facomec S.A 

COSTA RICA 

San José 

7 Tplffnnaktiphnlflnot I M EricSSOn 

ECUADOR 

Quito 

2. Teléfonos Ericsson C A 

GUATEMALA 

Guatemala City 


HAITI 

Port-au-Prince 

7. LM Encsson 

MEXICO 

Mexico D.F. 

1. Teleindustna Ericsson, S.A 

1. Latinoamericana de Cables S A 

de C V 

2. Teléfonos Ericsson S.A. 

2. Telemontaje, S.A. de C.V. 

PANAMA 

Panama City 

2. Telequipos S A 

PERU 

Lima 

2. Cia Ericsson S A 

EL SALVADOR 

San Salvador 

7. Teletonaktiebolaget LM Encsson 

URUGUAY 

Montevideo 

2. Cia Ericsson S.A. 

VENEZUELA 

Caracas 

1. Cla Anonima Ericsson 

Representatives in: 

Bolivia. Costa Rica, Dominican Republic, 

Guadeloupe, Guatemala. Guyana, Haiti, 

Honduras. Martinique, Netherlands Antilles, 

Nicaragua, Panama, Paraguay, El Salvador, 

Surinam, Trinidad. Tobago 

AFRICA 

ALGERIA 

Algiers 


EGYPT 

Cairo 


MOROCCO 

Casablanca 

4. Société Marocaine des Telephones et 

Telecommunications "SOTELEC" 

TUNISIA 

Tunis 


Zambia 

Lusaka 

2. Ericsson (Zambia Limited) 


Installation Branch 


Angola, Cameroon, Central African Republic, 

Chad, People's Republic of the Congo, 

Dahomey, Ethiopia, Gabon, Ivory Coast, 

Kenya, Liberia, Libya, Malagasy, Malawi, 

Mali, Malta, Mauretania, Mozambique, 

Niger, Nigeria, Republic of South Africa, 

Reunion, Senegal, Sudan, Tanzania. Togo, 

Tunisia, Uganda, Upper Volta, Zaire. 

ASIA 

INDIA 

Calcutta 

2. Ericsson India Limited 

INDONESIA 

Jakarta 

2. Ericsson Telephone Sales 

Corporation AB 

IRAQ 

Baghdad 


IRAN 

Teheran 

3. Simco Ericsson Ltd. 

4. Aktiebolaget Erifon 

KUWAIT 

Kuwait 


LEBANON 

Belrouth 

2. Société Libanaise des Telephones 

Ericsson 

MALAYSIA 

Shah Alam 

1. Telecommunication Manufacturers 

(Malaysia) SDN BHD 

OMAN 

Muscat 

7. Teletonaktiebolaget LM Encsson 

SAUDIARABIA 

Riyadh 

7. LM Ericsson 

THAILAND 

Bangkok 

2. Ericsson Telephone Corporation 

Far East AB 

TURKEY 

Ankara 

2. Ericsson Turk Ticaret Ltd Sirketi 

Representatives in: 

Bahrein, Bangladesh. Burma, Cyprus, Hong 

Kong, Iran, Iraq. Jordan, Kuwait, Lebanon, 

Macao, Nepal, Oman. Pakistan, Phillippines, 

Saudiarabia, Singapore, Sri Lanka, 

Syria, United Arab Emirates 

UNITED STATES and 

CANADA 

UNITED STATES 

Woodbury NY. 

2. LM Ericsson Telecommunications Inc 

New York, NY. 

5. The Ericsson Corporation 

CANADA 

Montreal 

2. LM Ericsson Limitée/Limited 

AUSTRALIA and 

OCEANIA 

Melbourne 

1. LM Ericsson Pty Ltd 

1. Rifa Pty. Ltd. 

5. Telenc Pty Ltd 

Sydney 

3. Conqueror Cables Ltd. 


New Caledonia, New Zealand, Tahiti. 

1. Sales company with manufacturing 

2. Sales and installation company 

3. Associated sales company with manufacturing 

4. Associated company with sales and 

installation 

5. Other company 

6. Other associated company 

7. Technical office

TELEFONAKTIEBOLAGET LM ERICSSON 

ISSN 0014-0171 fltinlnri in Cuiflrian I uinnlnra^non OrebfOl97!

Selection and Testing of Electronic Components for LM

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