geostationary telecommunications satellites electronic telephone set ...

ERICSSON 

REVIEW 

3 

1976 

GEOSTATIONARY TELECOMMUNICATIONS SATELLITES 

ELECTRONIC TELEPHONE SET-ERICOFON 700 

CCM-A WELL-TRIED AND ECONOMIC MAINTENANCE SYSTEM 

CCM IN THE DUTCH TELEPHONE NETWORK 

OPTIMIZATION OF POWER SUPPLY EQUIPMENT 

DEVELOPMENT AND PRODUCTION OF SOFTWARE FOR AKE 13

ERICSSON REVIEW 

NUMBER 3 • 1976 • VOLUME 53 

Copyright Telefonaktiebolaget LM Ericsson 

Printed in Sweden, Stockholm 1976 

RESPONSIBLE PUBLISHER DR. TECHN. CHRISTIAN JACOB/EUS 

EDITOR GUSTAF 0. DOUGLAS 

EDITORIAL STAFF FOLKE BERG 

BO SEIJMER (WORLDWIDE NEWS) 

EDITOR'S OFFICE S-126 25 STOCKHOLM 

SUBSCRIPTION ONE YEAR $6.00, ONE COPY $1.70 

Contents 

110 • Geostationary Telecommunications Satellites 

118 • Electronic Push-button Telephone Set — ERICOFON 700 

134 • CCM — A Well-tried and Economic Maintenance System 

138 • Ten Years Experience of CCM in the Dutch Telephone Network 

142 • Optimization of Power Supply Equipment for Modern 

Telecommunication Systems 

152 • Development, Production and Maintenance of Software for AKE 13 

161 • WORLDWIDE NEWS 

COVER 

ERICOFON 700 — A modern electronic 

push-button telephone set

Geostationary 

Telecommunications Satellites 

Harold A. Rosen 

At a ceremony held at the Museum of Technology in Stockholm on May 5th, 

1976 the LM Ericsson Prize was awarded for the first time. The recipient 

was Dr. Harold A. Rosen from Los Angeles. 

The prize and the prizewinner were introduced by the Chairman of the Prize 

Committee, Dr. Hkkan Sterky, whose introduction can be summarized 

as follows: 

In 1975 the LM Ericsson Board of directors decided to institute a prize of 100,000 

Swedish crowns for significant contributions within telecommunications 

engineering. According to the statutes the prize shall be awarded every third 

year to a person who in the last three-year period has made an specially 

important scientific or technological contribution within telecommunications 

engineering or who has earlier made such contributions which, in the course 

of the period, have proved to be of this nature. 

The Prize Committee consists of three members and works quite independently 

of the LM Ericsson Board of directors and President, and is sovreign in its 

selection of prizewinner. Candidates are to be nominated before October 1st 

the year before the prize is awarded. In 1974, 74 candidates were nominated 

by 47 experts in the field of telecommunications engineering. 

Dr. Rosen was born in New Orleans, Louisiana, in 1926 and studied at Tulane 

University and California Institute of Technology. He is now vice president 

of Huges Aircraft Company, Space and Communications Group. He holds 

a number of patents and has been awarded many honorary distinctions. 

After the introduction Dr. Rosen presented a paper on geostationary 

telecommunications satellites, which is presented here. At the subsequent 

prize ceremony the LM Ericsson Prize was presented to Dr. Rosen by 

King Carl XVI Gustaf. 

UDC 621 396 546 

629.783 

LME 858 

Geostationary telecommunications satellites 

have resulted from a successful 

blend of controllable rocket and radio 

repeater technologies. The creative 

ideas and thoughtful experiments of 

many men from many countries have 

yielded the engineering basis of today's 

spacecraft, and I would like to 

pay tribute to a few of them while recounting 

the significant events leading 

to the global and domestic systems 

currently in use. 

Before describing the satellites, a few 

words about the launch vehicles are 

appropriate. The efficient launchers 

now in use owe their origins to the 

early rocket experimenters. Although 

solid propellant rockets have been 

known and used for centuries, it remained 

for the theoretical studies and 

test firings of gyroscopically controlled 

rockets in the 1920's and 1930's by the 

American university professor Robert 

H. Goddard to demonstrate the feasibility 

of liquid propulsion, the primary 

propulsion system of most of today's 

launch vehicles, which for communications 

satellites are primarily Delta and 

Centaur rockets. In a theoretical paper 

in 1929, the Austrian engineer Hermann 

Noordung gave the first description of 

the properties of the geostationary orbit. 

He showed that if a satellite were 

rocketed into a circular equatorial 

orbit at an altitude of 36,000 kilometers, 

where its orbital period would be 24 

hours, it would appear stationary relative 

to the earth, as if supported by a 

gigantic tower. 

The first description of a communications 

satellite system is due to the prophetic 

vision of the English scientist 

and writer Arthur C. Clarke, who in 

1945 showed how if suitable radio 

equipment were placed in a geostationary 

orbit it could provide continuous 

worldwide radio coverage. He 

recognized not only the possibility of 

satellite communications but its importance 

to the world and proposed 

that such a system be developed. 

The American scientist and engineer J. 

R. Pierce described long distance 

communications systems based on 

orbiting radio relays of various types 

and altitudes in a paper published in 

1955, the last sentence of which reads, 

"At this point, some information from 

astronomers about orbits and from 

rocket men about constructing and 

placing satellites would be decidedly 

welcome." Two years later, the Russian 

rocket men partly satisfied his curiosity 

with the launching of Sputnik, the 

first artificial satellite. 

This starting event in 1957 stimulated 

more activity than any other toward 

the realization of practical spacecraft. 

Among other things, it led to the beginning 

of a large American space 

program and the awareness on the 

part of many, previously oblivious to 

space, of its promise. I was one of 

those so stimulated, and while perusing 

the subject in 1959, I came 

across an elaboration by Dr. Pierce 

and Rudolph Kompfner on transoceanic 

communication by satellite. This article 

described many configurations, 

including the geostationary system 

previously envisioned by Clarke, and 

pointed out its benefits as well as some 

of its Droblems.

111 

HAROLD A. ROSEN 

Vice President 

Hughes Aircraft Company, USA 

In contrast to all other orbits, the geostationary 

orbit permits continuous 

communications over vast areas via a 

single satellite and requires little, if 

any, tracking capability in the associated 

earth terminals. Thus, potentially 

large cost savings in both the orbiting 

and earthbased elements of a 

satellite communications system would 

accrue when geostationary satellites 

were available. However, in 1959 the 

prospects of early achievement of this 

goal were bleak. Many problems resulted 

from the size and complexity of 

the designs then being considered. 

The large size precluded the use of 

launch vehicles available at that time; 

but, even if launchable, these designs 

were too complex to have an economically 

attractive life expectancy. 

While pondering these matters, it occurred 

to me that the satellite's size 

and complexity could be greatly reduced 

if a spinning configuration were 

adopted. This would provide stabilization 

of a toroidal antenna beam which 

continuously encompassed the earth, 

simplifying the attitude control, while 

permitting orbital period control by use 

of spin phased impulses, thus simplifying 

the orbit control system. Additional 

savings in weight could be 

achieved by the use of a solid state 

receiver for the communications receiver 

and a traveling wave tube amplifier 

for the transmitter, an invention 

of Kompfner's perfected by Pierce. 

These design concepts provided the 

basis for a lightweight geostationary 

communications satellite design; and, 

starting in the fall of 1959, I led a small 

team charged with perfecting and reducing 

it to practice. My late colleaugue, 

Donald Williams, was responsible 

for the orbit and attitude control 

system design and analysis, and, 

among many other contributions, invented 

a method of attitude control 

using a single thruster, which he demonstrated 

with a dynamic model in 

1960. The entire attitude and orbit control 

of the satellite could now be accomplished 

with only two thrusters, 

using spin phased impulses when necessary. 

My friend and coworker, Thomas 

Hudspeth, was responsible for the 

receiver and antenna development and 

designed efficient, lightweight elements 

years ahead of their time. John 

Mendel adapted the traveling wave 

tube transmitter to space applications 

by perfecting a rugged, lightweight 

design featuring metal-ceramic construction 

and periodic permanent magnet 

focusing. With these elements, we 

proceeded to construct and test a prototype 

geostationary satellite during 

the year 1960, an effort supported by 

Hughes Aircraft Company, and also 

began a campaign to get it launched. 

Our initial proposals were turned down 

by all U.S. Government agencies and 

every communications company that 

was approached. An unsuccessful attempt 

to interest European agencies 

and communications companies in the 

idea centered on the Paris Air Show of 

1961 and a subsequent demonstration 

on the Eiffel Tower, where it was alleged 

that "this is as high as it will ever 

get". The general feeling of skepticism 

expressed both in the United States 

and Europe involved doubts about the 

technical approach as well as the quality 

of voice communications via a geostationary 

satellite. The latter objection 

was raised because of the propagation 

time delay associated with the 

high altitude orbit, and its adverse interaction 

with the echo suppressors 

used in the ground networks. However, 

continued tests on this question showed 

that the time delay could be acceptable 

when the voice circuits were 

equipped with properly designed echo 

suppressors, and was of no consequence 

for television and telegraphic 

communications. 

After additional persuasion, late in 

1961 the U.S. Space Agency, NASA, 

with cooperation from the Department 

of Defense, sponsored a program to 

test the concept—this became known 

as the Syncom program, for Synchronous 

Communications. While the flight 

models of Syncom were being constructed 

and tested in the summer of 

1962, Telstar, which was constructed 

by Bell Telephone Laboratories of 

AT&T, was launched by NASA into a 

low altitude orbit and first demonstrated 

the feasibility of wideband transoceanic 

communications via satellite. 

The first Syncom satellite was launched 

in February 1963 but exploded when 

injected into final orbit and became

112 

forever silent. The next launch attempt 

was made that July. Everything worked 

perfectly on Syncom II, and communications 

was successfully demonstrated 

via a synchronous but not geostationary 

satellite (since the orbit was 

inclined relative to the equator). The 

first geostationary orbit was achieved 

in 1964 with the launch of Syncom III 

into an equatorial synchronous orbit; 

among other things, it carried television 

transmissions of the Tokyo Olympics 

across the Pacific. 

Coincident with the first Syncom 

launch, the U.S. Comsat Corporation 

was formed for the purpose of engaging 

in commercial communications 

via satellite. Noting the success of 

Syncom, Comsat entered into a contract 

for the construction of an experimental 

operational satellite of similar 

design to be used in transatlantic 

service by INTELSAT, the International 

Telecommunications Satellite Consortium 

(now Organization), which would 

be formed in time to use the new satellite. 

In the spring of 1965, Intelsat I, 

also known as Early Bird, was launched 

and inaugurated commercial intercontinental 

communications of voice, 

telegraph, and television traffic via 

satellite. 

While Early Bird was being constructed, 

NASA was sponsoring the development 

of still higher performance 

satellites in its Applications Technology 

Satellite series. Additional communications 

capacity could be achieved 

by using pencil beam antennas to 

replace the lower gain toroidal beam 

heretofore used. The ATS satellites 

demonstrated both electronic and 

mechanical means of despinning these 

beams to illuminate the earth continuously 

from the spinning satellite. The 

ATS satellite also took the first pictures 

of the full disc of the earth from synchronous 

orbit by use of a spin-scan 

cloud camera. Early Bird was followed 

in 1966 by Intelsat II, a larger and 

slightly higher capacity satellite, and 

in 1968 by Intelsat III, which featured 

a mechanically despun pencil beam 

antenna and completed the first truly 

global system for INTELSAT with yet 

higher capacity. 

In 1969 an experimental high 

power 

satellite designed to provide service 

to ships and airplanes was launched 

by the U.S. Department of Defense. 

Called TACSAT, it featured a new dual 

spin configuration which provided 

greater flexibility in the communications 

and mechanical design areas 

than the earlier spinners by relaxing 

some of the geometric constraints. 

The method of stabilizing this configuration 

was invented by Anthony 

lorillo. This design feature was incorporated 

into the high capacity Intelsat 

IV series which began service in 1971, 

and whose six currently operating satellites 

carry the bulk of INTELSAT'S 

traffic. The Intelsat orbiting fleet is at 

present being augmented by the still 

further advanced and higher capacity 

Intelsat IVA, two of which have been 

launched within the last few months. 

The additional capacity of Intelsat IVA 

was achieved by the development of a 

multibeam antenna with east-west 

isolation, which makes it possible to 

reuse the frequency spectrum. The 

antenna, its feed distribution system, 

and the transmitter compartment are 

today's standard for satellite engineering. 

The Intelsat satellites currently 

carry all transoceanic television and 

most of the international telephonic 

communications, in conjunction with a 

complex of 123 earth stations located 

in 71 of the 92 member nations of IN 

TELSAT. 

As the economy of communications 

via satellite steadily improved through 

technological change in the Iate1960's, 

it became apparent that not only international 

but also intranational communication 

could be achieved on a cost 

competitive basis by use of satellites 

in certain countries. Canada became 

the first country to implement a national 

satellite system with the inaugural 

use of Anik by its Telesat Corporation 

in 1972. The large antenna used 

on Anik generated an antenna beam 

which concentrated much of the satellite's 

radiation within the borders of 

Canada, thus providing substantial 

communications capacity via a relatively 

small and low cost satellite. The 

three Anik satellites now provide dual 

language television distribution and 

thin-route telephonic service to the 

sparsely populated portions of Canada, 

as well as conventional communica-

113 

tions service to the more densely 

populated areas. The Western Union 

Company has provided general communications 

service to the United 

States since the launch of a similar 

satellite, called Westar, in 1974. Indonesia 

is currently implementing the 

ground terminals for its national system 

which is expected to begin operations 

following the launch of its first 

satellite, called Palapa, in July of this 

year. 

In addition to international and national 

communications systems, satellites 

are expected to play an increasing 

role in providing mobile communications 

service to ships and airplanes. 

TheMarisat satellite launched thisyear 

in February has begun service to U.S. 

Navy ships on a regular basis, and 

service will be offered to commercial 

shipping later this year when additional 

Marisats are planned to be in 

operation. 

Since the signals from national satellites 

can be concentrated within a nation's 

boundaries, smaller antennas 

can be used at earth terminals than for 

satellites whose energy is more widely 

dispersed. This fact, coupled with the 

steady improvement in the performance 

of low cost receivers, has made 

it possible to build television reception 

terminals at a small fraction of the 

cost of general-purpose international 

terminals, and these costs are rapidly 

decreasing. Thus, widespread television 

distribution via national satellite 

systems for education and cultural enrichment 

is becoming steadily more 

attractive economically, and this use 

of satellite communications may yet 

become the most important application 

of all for geostationary communications 

satellites. 

The figures on pages 114—777 illustrated 

Dr. Rosen's paper.

114 

Figs. 1—4 Figs. 5—8

Figs. 9—12 Figs. 13—16 

115

116 

Figs. 17—20 Figs. 21—24

Figs. 25—28 Figs. 29—32 

117

Electronic 

Push-button Telephone Set 

-ERICOFON700 

Arne Boeryd, Leif Branden, Jan-Olof Hedman and Olle Larsson 

The telephone sets designed by LM Ericsson in 1892 and 1931 were trend-setters. 

The sets used today by telephone administrations all over the world are 

developments of the 1931 model. Naturally there are differences as regards 

design and construction, but the basic features are the same. LM Ericsson's 

latest design on the lines of this basic model is the well-known telephone set 

DIALOG, which was introduced on the international market in 1962. 

LM Ericsson's one-piece set ERICOFON, which was introduced in 1956, 

was a pioneer not only because of its unique and functional shape but primarily 

because this model enabled the telephone administrations to offer the 

subscribers an alternative to the traditional type of set. The commercial success 

evinced by ERICOFON is the best proof of the subscribers' appreciation of 

the appearance, technical quality and easy handling of the set. 

UDC 621.395.721: 

621.395.6361 

LME 822 

Design requirements 

The technical development of material 

and components that took place up to 

a few years ago continuously affected 

the telephone sets, which were revised 

and improved. However, this continuous 

development did not usually provide 

scope for the introduction of 

completely new techniques or for offering 

new services and facilities. 

However, the landslide development 

that has taken place in semiconductor 

engineering during the last few years 

has meant that telephone subscribers 

can now be offered several new facilities 

and greatly improved transmission 

quality in the telephone set, irrespective 

of to which subscriber line or local 

exchange the subscriber is connected. 

Hitherto it has only been possible to 

offer push-button dialling to a limited 

number of subscribers, connected to 

new or modified local exchanges. The 

results of field trials and the enthusiastic 

reception push-button dialling has 

received in the countries (the U.S. and 

Canada) where it has been offered for 

some time as an alternative to conventional 

dialling, testify to the advantages 

the method gives the subscriber. Impulsing 

is faster, more reliable and 

easier from the subscriber's point of 

view, and at the same time the register 

holding time in the exchange is reduced, 

with increased availability in 

the telephone network as a result. 

The development of memory and counter 

circuits in MOS technology has 

paved the way for the possibility of 

transforming a push-button code to 

decadic impulsing at an arbitrary frequency 

(10—20 Hz). This development 

makes it possible to offer all subscrib- 

Fig. 1 

ERICOFON 700

119 

ARNE BOERYD 

LEIF BRANDEN 

JAN-OLOF HEDMAN 

OLLE LARSSON 

Subscriber Equipment Division 

Telefonaktiebolaget LM Ericsson 

ers push-button dialling, irrespective 

of the type of local exchange. A new 

telephone set can therefore be designed 

for only push-button dialling. 

The transmission components in the 

telephone sets have been subjected to 

intense revision work during the last 

few years. This applies both as regards 

the microphone and the receiver, and 

also the transmission circuits. The 

work has resulted in a miniaturized 

microphone and receiver, and a replacement 

for the passive speech circuit 

has been developed, an electronic 

speech circuit with the necessary active 

amplifier elements integrated with 

the required passive piece parts. 

Fig. 2 

ERICOFON 700, exploded view

The bottom part (frame) ot the set 

Push-button dialling mechanism 

1. Common contact spring assembly 

2. Slide 

3. Switching bar 

Fig. 5 

Cradle switch mechanism 

1. Contact spring assembly 

2. Arms 

3. Return spring 


5. Cradle key 


7. Cradle buttons 

The signalling device of the telephone 

set, the bell, has in certain cases already 

been replaced by a tone ringer, 

either with a separate electroacoustic 

signal generator or with the receiver 

or microphone as the sound transmitter. 

The advantages of tone ringing are 

a more pleasant but at the same time 

more penetrating signal, and a unit 

that, from the design point of view, requires 

less space than a conventional 

bell. 

Apart from the advantages as regards 

function and quality, a design using 

modern electronic technology with integrated 

circuits also means a substantial 

reduction in the weight of the set. 

In connection with the centenary of the 

telephone and of LM Ericsson, the 

company introduced the first wholly 

electronic one-piece telephone set. 

The exterior of the set has the classical 

shape of ERICOFON. 

Mechanical design and 

construction 

The new telephone set, ERICOFON 

700, consists of two main parts, the 

bottom part and the case. The bottom 

part contains the push-button set, 

cradle mechanism including the cradle 

contact spring assembly, microphone, 

transmission printed board assembly 

and a ring unit. The case holds 

the impulsing printed board assembly 

and receiver. 

Two characteristic features of all subcomponents 

in ERICOFON 700 are low 

weight and smali volume. Special attention 

has been paid to the design of 

the cradle mechanism and the cradle 

contact spring assembly in order to 

achieve both low weight and high reliability 

even if the set is placed on an 

uneven surface. 

A one-piece set with all components 

in the "handset" puts great demands 

on the mechanical stability of the set. 

The main construction principle has 

therefore been to make the set and the 

mountings for the various parts relatively 

elastic in relation to each other 

in order to provide shock absorption. 

The various units of the set consist of 

functional blocks that can be tested 

individually during manufacture and 

replaced individually during maintenance. 

The construction of the set is shown in 

detail in fig. 2. 

As has already been mentioned, the 

set consists of two main parts, insert 

(bottom part) and case. The two parts 

plug into each other and are held together 

by three screws. 

THE INSERT 

The insert consists of the following 

parts: 

• Frame with gasket 


• Cradle mechanism 

• Recall button (R) 

] Transmission unit 

n Ring unit 

• Cord 

Frame with gasket 

The frame, fig. 3, supports all the structural 

parts of the set. The frame has 

been designed with regard to the 

stringent mechanical strength requirements. 

It is injection moulded in ABS 

plastic. The frame is always black 

irrespective of the colour of the case. 

In order to protect the surface on 

which the set is placed, the underside 

of the frame is provided with a gasket 

made of injection moulded polyuretane, 

a material that does not affect or 

discolour varnished surfaces. 


During the 1960s LM Ericsson developed 

a push-button dialling mechanism 

for the internationally recommended 

V.F. code signalling system. 

This mechanism, has previously been 

described in Ericsson Review'. At that 

time there were several other pushbutton 

dialling systems in existence, 

with different "dialling" mechanisms. 

The production volumes per system 

were fairly small, which meant that 

special push-button sets were rather 

expensive.

121 

Fig. 6 

Cradle contact spring assembly 

1. Frame 

2. Contact strip 

3. Contact springs 

4. Spacer 

5. Camshaft 

6. Lid 

7. Screw 

During the development of ERICOFON 

700 the basic principle was therefore 

adopted that it should be possible 

to use the same push-button dialling 

mechanism for all existing automatic 

telephone systems. The mechanism 

works in accordance with the same 

principles as that for V.F. code signalling. 

In the impulsing unit push-button 

signals are converted to the signalling 

codes of the various automatic telephone 

systems—V.F. code, d.c. impulsing 

(instead of a conventional dial) 

etc. 

Cradle mechanism 

The cradle mechanism (fig. 5) is activated 

at three points, which are 

placed symmetrically around the pushbutton 

dialling mechanism, namely by 

a long key on the front of the set, which 

activates the two switching bars and 

also by two buttons in the rear part of 

the set, which operate one switching 

bar each. The vertical movement of the 

cradle buttons is transformed by the 

switching bars into a torsional movement, 

which is transferred to the actuating 

device of the cradle contact 

spring assembly. 

Cradle contact spring assembly 

The requirements regarding low weight 

for ERICOFON 700, compact structure 

and a large number of contact functions, 

led to a new design of the contact 

spring assembly. The design requirements 

for this unit were: 

— small dimensions 

— low operating force 

—• large movement margins before 

and after contact occurrences 

— contact functions consisting of 

four changeovers, alternatively four 

make-before-break contacts with 

requirements for time sequence between 

the contact occurrences 

— a design adapted for mounting on 

a printed circuit board. 

The contact spring assembly, fig. 6, 

contains four separate break contacts 

and four separate make contacts, 

which can be connected to form four 

make-before-break or changeovers. By 

changing the camshaft, within the 

limits of eight contact functions, the 

desired number of closures, breaks 

or changeovers can be obtained, fig. 7. 

The construction of the contact spring 

assembly, with a turning camshaft that 

works upon the springs, makes possible 

large movement margins both before 

and after the contact occurrences 

without requiring largeractuating force 

or increasing the stress on the springs. 

The desired time sequence of the 

various contact occurrences is obtained 

through a suitable design of the 

camshaft, fig. 11. 

In view of the low voltage of electronic 

circuits, silver palladium contacts are 

used.

Fig. 10 

Buzzer unit 

Fig. 9 

Tone ringing unit 

Recall button (R button), 

number frame 

In order to simplify the operation of the 

set as much as possible it was necessary 

to reduce the number of function 

elements to a minimum. For this reason 

the number frame and the recall 

button have been combined to form 

one unit. 

Pos. 1 in fig. 2 shows the button for 

calling a register. The number frame, 

pos. 2, is mounted over the R button 

with one end carried in a bearing. The 

R button is actuated by pressure on 

the other end of the number frame. In 

these cases where the R button is not 

required, the number frame is fixed. 

The number frame is mounted with the 

aid of a snap-on device on the frame. 

Transmission circuit unit 

Pos. 3 in fig. 2 shows the transmission 

circuit unit, fig. 8. The unit contains the 

electronic speech circuit, electret microphone 

and cradle contact spring assembly. 

The electret microphone and 

the speech circuit are mounted in a 

common plastic cover. The cover is 

injection moulded. The speech circuit 

is protected against amplitude modulated 

radio signals. The transmission 

circuit also contains the necessary 

connection screws for the instrument 

cord. 

The printed circuit board is a doublefoil 

board of glass fibre reinforced 

epoxy laminate with plated-through 

holes. 

Ring unit 

The ring unit (pos. 4 in fig. 2) is available 

in three alternative versions: for 

tone ringing, with an electromechanical 

buzzer and as a connection unit 

without any internal calling device (an 

external calling device, not associated 

with the set, is used). The ring unit always 

contains the jack that connects 

the insert of the set with the impulsing 

electronics and the receiver, which 

are mounted in the case. Fig. 9 shows 

the tone ringing unit and fig. 10 the unit 

for electromechanical buzzer. 

Telephone cord 

The telephone cord (pos. 12 in fig. 2) is 

of a standard type with colour-coded 

tinsel conductors with a PVC sheath. 

Each conductor consists of four-wire, 

double-tape cadmium-copper tapes 

wound round a polyester core. A part 

of the cord is coiled and its normal 

length is 1.3 m. Fully extended it measures 

2.4 m. It is fixed to the frame with 

mechanical stress relief. The connectors 

are terminated in cable lugs for 

screw connection. 

Mounting the insert 

The push-button dialling mechanism is 

screwed into the frame with the aid of 

two distance pieces which also constitute 

the holders for the transmission 

Fig. 8 

Transmission unit 

Fig. 7 

Cradle contact assembly, wiring diagram 

MAKE-BEFORE-BREAK CONTACT 

1 and 3 or 1 and 4 are connected together. 

When the camshaft turns, 1 and 2 close before 

3 and 4 break 

ORDINARY CHANGEOVER 

2 and 3 or 1 and 4 are connected together. 

When the camshaft turns, 3 and 4 break before 1 

and 2 close

123 

Fig. 11 

Cradle contact spring assembly, functional 

diagram 

Y///A 

Closed contacts 

A a Torsional angle of the camshaft when It 

turns from position 1 to position 2

Fig. 12 

Impulsing unit 

and ring units. Between the transmission 

unit and the ring unit a spacer has 

been inserted, which insulates the two 

printed board assemblies from each 

other. 

CASE 

The case contains the impulsing electronics, 

the receiver with the associated 

cap and a fixing device for these. 

The case and receiver cap are made 

of injection moulded ABS plastic in 

several different colours. 

Impulsing unit 

Pos. 5, fig. 2 shows the impulsing unit. 

The printed circuit board is made of 

glass fibre reinforced epoxy laminate 

with copper foil for conductive patterns 

on both sides and with platedthrough 

holes for the components. 

Both the printed board assemblies for 

decadic pulse signalling and the one 

for V.F. code signalling are encased in 

a shrink tube. Thus the components 

are well protected against mechanical 

shocks to which the set may be subjected. 

The printed board assembly contains 

a spring holder for the receiver (pos. 6 

and 7, fig. 2). The impulsing unit is 

shown in fig. 12. 

Fitting the case 

The impulsing unit with the receiver is 

inserted in the case. The unit is fixed 

with the aid of a mechanical spring 

screwed to the case, after which the 

receiver cap is snapped on. The receiver 

cap can be removed and the impulsing 

unit removed from the case for 

maintenance purposes. 

Electroacoustics and circuit 

constructions 

ALTERNATIVE MICROPHONE 

PRINCIPLES 

For several years linear microphones 

with the required amplifiers have been 

used to replace carbon microphones 

in telephone sets. Various microphone 

elements have then been thoroughly 

analyzed, studied and tested in field 

trials. Their advantages and disadvantages 

have been compared. The 

electroacoustic converters that are 

suitable for use in the future are mainly 

the following types: 

] electromagnetic 

electrodynamic 

electret 

• piezoelectric 

LM Ericsson have more than 90 years' 

experience of the electromagnetic 

converter as a receiver component. 

Thus it seems natural to use the same 

element for both the microphone and 

the receiver. In those cases where 

volume and weight are not of major 

importance this solution offers certain 

advantages. However, if the smallest 

possible units are desired, especially 

as regards the microphone, and small 

electrodynamic or electromagnetic 

elements are therefore chosen, the efficiency 

will be reduced. Alternatively 

it may be necessary to work with extremely 

small air gaps in the magnet 

circuits, which may easily disturb the 

mechanical stability. If the alternative 

with lower efficiency is chosen, it will 

be necessary to increase the amplification, 

which may be difficult to achieve 

without distortion, in view of the available 

d.c. power. 

Electrets and piezoelectric elements 

have a lot in common. They can be 

miniaturized while retaining high efficiency, 

and they can be manufactured 

at a relatively low cost. The disadvantages 

of piezoelectric elements in the 

form of ceramic plates is their sensitivity 

to mechanical shocks and vibrations. 

Moreover the piezo-ceramic element 

has a pronounced resonant frequency, 

which can cause design difficulties 

when dimensioning the frequency 

curve of the microphone. 

The electret element is insensitive to 

mechanical vibrations. It is easy to obtain 

the desired frequency curve by 

means of simple measures. The material 

cost of the element is low. The 

main disadvantage of the electret element 

has previously been a certain 

sensitivity to increased temperature 

and humidity. In view of the mainly advantageous 

properties of the electret 

microphone, LM Ericsson and the 

Swedish Telecommunications Administration 

have decided to continue the 

develoDment of the electret orinciDle

125 

jointly with the aim of counteracting 

the disadvantages at higher temperature 

and humidity. 

Electret microphone 

The electret microphone, fig. 13, is in 

principle a capacitor microphone, in 

which the electric field is generated by 

a charge in the diaphragm material instead 

of a d.c. voltage applied from 

outside. The electret itself consists of 

a dielectric that retains an electric 

charge after it has been exposed to a 

strong electric field. 

The work on developing electret microphones 

for use in telephone sets 

has mainly been directed towards obtaining 

electrets having guaranteed 

good ageing properties in severe environmental 

conditions. By comparing 

the measurable properties of the electret 

itself with the properties of the 

microphone element at increased temperature 

and humidity and during 

highly accelerated tests during manufacture, 

a reliable way of checking the 

electret has been obtained. 

In a normal environment, which is 

where 90—95 per cent of all telephone 

sets are used, the life of the electret 

should be infinitely long, and under 

severe environmental conditions its 

life is many times that of the carbon 

microphone. 

RECEIVER 

The construction of the receiver (pos. 

7, fig. 2) is shown in detail in fig. 14. 

The receiver construction is the result 

of development work on the traditional 

bipolar electromagnetic receiver and 

it is of the same type as that used in 

DIALOG for the last few years. 

TRANSMISSION CIRCUIT 

Fig. 15 shows the block diagram of the 

transmission circuit. In principle the 

circuit is constructed as a Wheatstone 

bridge with the local line connected at 

points A and B. The local line (ZL) 

then forms one arm of the bridge. Two 

of the arms of the bridge consist of 

resistances (Z1 and Z2) and the fourth 

arm consists of the balance impedance 

ZB, which within certain limits takes up 

the same value as ZL. The bridge is 

balanced when ZL : ZB = Z1 : Z2. The 

output of the microphone amplifier is 

connected to the bridge points B and 

E. The receiver amplifier is d.c. connected 

and fed from the telephone line 

through Z1, Z2 and ZB. One line branch 

(A) is connected direct to the signal input 

of the receiver amplifier. Capacitor 

C1 gives a.c. short-circuiting of points 

C and D. The incoming speech signals 

are amplified in the receiver amplifier 

(AR). Extremely high signal levels and/ 

or high transients are symmetrically 

limited by the receiver amplifier in order 

to avoid acoustic shocks in the receiver. 

Fig. 13 

Electret microphone 

1. Outer cover 

2. Cap 

3. Diaphragm 

4. Electret foil 

5. Electrode 

6. Contact ring 

7. Frame 

8. Contact ring 

Fig. 14 

Receiver 

1. Jacket 

2. Spacer ring 

3. Cap 

4. Diaphragm 

5. Armature 

6. Coil 

7. Magnet 

8. Pole piece 

9. Plate 

10. Frame 

11. Fuse metal

126 

Fig. 15 

Transmission diagram 

Fig. 16 (right) 

Transmission diagram with automatic level 

regulation. Sending and receiving 

The microphone signal is amplified in 

the microphone amplifier (AM) and is 

fed out to the line at points B and E, 

which also constitute feeding points 

for the direct current to the microphone 

amplifier. 

The speech circuit introduced in ERI- 

COFON 700 has no transmission regulation. 

However, as the feeding loss 

of the microphone is eliminated (constant 

amplification of direct currents 

from 100 mA down to < 10 mA), the 

transmission characteristics of the 

non-regulated circuit are better than 

those of the traditional carbon set. 

Further improvement of the transmission 

characteristics of the set can be 

obtained by introducing regulation of 

the sending and receiving level, which 

compensates the speech frequency attenuation 

caused by the subscriber 

line in accordance with the following 

principle. 

A constant sending or receiving level 

irrespective of the attenuation of the 

subscriber line is obtained by introducing 

attenuation networks, Z3 and 

Z4 respectively in fig. 16. The value of 

the impedance Z3 or Z4 is a function 

of the direct current on the line. When 

the line current is high, i.e. a short line, 

the impedance is low and the level to 

the microphone or receiver amplifier is 

attenuated. When the length of the line 

increases and the direct current decreases, 

the impedance in the shunt 

circuit increases and a constant level 

that is not dependent on the length of 

line is obtained in the local exchange 

when sending and in the receiver when 

receiving. All semiconductor elements 

for the microphone and receiver and 

for transmission regulation, as well as 

the majority of the required resistances, 

are assembled in one monolithic 

circuit. The monolithic circuit and 

the required capacitors are mounted 

on a thick film substrate, utilizing the 

possibilities offered by the thick film 

network for trimming to the nominal 

amplification and for adaptation to different 

current feed systems. The transmission 

circuit is encapsulated in polyuretane, 

chosen for its good resistance 

to temperature variations. The 

size of the complete unit is 7x20X35 

mm. The transmission circuit is also 

electrically protected against transients 

by an external 15 V zener diode. 

IMPULSING UNIT 

Circuit components 

It was necessary to integrate many of 

the various functions of the impulsing 

unit. Fig. 17 shows a block diagram of 

the unit. 

The only discrete components used 

are capacitors and the diodes and resistors 

that could not be integrated in 

the blocks to which they belong, for 

example because of high precision requirements. 

The impulsing unit is protected 

against fast transients by a 

100 V zener diode. 

Functional description 

The memory circuit with the associated 

logic, V1, is built up around a 4- 

phase dynamic shift register having a 

capacity of 20 figures. Two of the four 

clock pulses (01 and 03) come from 

the clock and control circuit V4, and 

the other two (02 and 04) are generat-

127 

ed internally in V1. The logic levels are 

0 and —4 V. 

The number information from the pushbutton 

set comes in on inputs P1—P4, 

and at the same time the common contact 

of the set gives a control signal to 

the anti-bounce logic via P5. 

The anti-bounce protection consists of 

a 5 ms delay before the number code 

is accepted for decoding and verification. 

The output of pulses starts immediately 

after the first digit has been accepted. 

A special register (marker) 

checks that the digits are fed out in 

the right order. 

The output signals consist of a control 

signal to the switch that disconnects 

the transmission circuit, and 

trigger signals to the impulsing switch. 

All the relevant frequencies and breakmake 

ratios can be obtained by external 

strapping. 

The oscillator, 10, oscillates at 4 V at a 

frequency of 18 kHz. It provides both 

trigger signals to 12 for the clock pulses 

01 and 03, and for feeding the 

cascade generator, 11. 

The cascade generator is a diode capacitance 

ladder, which transforms 

4 V a.c. to 15 V d.c. for feeding the 

clearing and pulse shaping circuit. 

The clearing and pulse shaping circuit, 

12, gives the 15 V clock pulses with 

rapid rise and decay times that the memory 

unit requires. It also contains a 

clearing circuit that initially clears the 

memory of all the (probably erroneous) 

information that the circuit may have 

recorded before the operating voltage 

reached its set value (12.5 V). This ensures 

that the information fed into the 

memory is correct. 

The line adaptation circuit, 6, consists 

of transistor switches that disconnect 

the transmission circuit and which also 

impulse. 

The transmission switch is normally 

conducting. In its cut-off state the impulsing 

switch conducts sufficiently to 

maintain a certain charge on the capacitor 

that drives the oscillator during 

the impulsing and to make the transmission 

switch conducting. This "leakage" 

across the line takes up to about 

1 mA of the line current. From an a.c. 

point of view the line is thereby shunt- 

Fig. 17 

Impulsing unit. Block diagram 

1. Contact bounce logic 

2. Output logic 

3. Input decoder 

4. Shift register 4x20 bits 

5. Secondary frequency divider 

6. Line adaptation circuit 

7. Check register 

8. Control logic 

9. Primary frequency logic and inter-digit 

pause logic 

10. RC oscillator 

11. Cascade generator 

12. Zero setting and pulse shaping circuit 

13. Transmission circuit

128 

ed by about 100 kohms. In order to 

maintain this leakage the voltage between 

the output of the transmission 

switch and Lb must not be less than 

2.5 V. With high speech levels the 

transmission circuit can momentarily 

fall to 1 V. For this reason two diodes 

have been connected in series with the 

output of the transmission switch. The 

voltage drop that the impulsing unit 

thereby introduces in series with the 

transmission circuit is less than 2 V 

(two diodes + the bottom voltage in a 

Darlington stage). There is also a resistance 

of about 25 ohms in the overvoltage 

protection. This also limits the 

current through the transmission circuit 

to a maximum of 200 mA. 

The impulsing circuits are included in 

a thick film circuit, which also contains 

a regulating function for maintaining 

the capacitor voltage at 4 V 

during impulsing. 

Tone ringing unit 

As has been mentioned previously, 

ERICOFON 700 has different versions 

of signalling device. The set can of 

course be connected to any existing 

type of external signalling device. The 

signalling device built into the set consists 

of either an electromagnetic buzzer 

or a tone ringing set. In the tone 

ringing version the receiver of the set 

is used as the signalling medium. 

The electronic parts of the tone ringing 

circuit are assembled in an integrated 

thick film circuit. The capacitors 

required in the circuit are mounted as 

discrete components by the side of the 

thick film circuit. Fig. 18 shows the 

block diagram of the tone ringing circuit. 

The signal is modulated by the ringing 

frequency and capacitor C1 affects the 

modulation factor. The circuit has a 

high impedance at low signal levels 

(speech signals) so that it does not 

load the transmission circuit. Since the 

receiver is used as a signalling device, 

a zener diode, D1, which limits the output 

level to the receiver, has been included. 

Thus different values for the 

zener diode give different acoustic output 

levels. 

C5 gives a start delay of 100 ms to reduce 

tinkling in parallel sets and other 

undesirable noise. The circuit works 

as a relaxation oscillator. The oscil- 

Fig. 18 

Tone ringing unit

Fig. 19 

Overvoltage protection 

1. Discharge valve 

2. Attenuating resistor 

3. Zener diode 

-C=r 

::• 

lator output is almost a square wave 

with a frequency of about 750 Hz. 

The frequency is influenced by capacitor 

C2 and the harmonic content by 

C3. The start voltage for an even and 

clear signal amounts to about 20 V for 

the low impedance tone ringer and 

about 40 V for the high impedance tone 

ringer (connected in parallel with the 

line). 

Overvoltage and transient protection 

An electronic set naturally requires another 

type of overvoltage protection 

than a conventional telephone set. 

There is also a certain risk that nonlinear 

elements with high impedance 

in the circuits can detect amplitudemodulated 

radio frequencies. Special 

attention has therefore been given to 

the elimination of both overvoltage 

damage and radio detection. 

Protection against radio detection 

A problem that always arises when 

high-impedance semiconducting elements 

are used in telephone sets is 

the radio signal detection that can occur 

in these components. Experience 

from field trials in various parts of 

Scandinavia shows that the main problem 

is induced disturbances between 

the telephone line and earth potential 

and mainly concerns radio frequencies 

in the range 0.25—1 MHz. The risk of 

any such disturbances has been effectively 

eliminated in ERICOFON 700 by 

the following measures: 

— The microphone and amplifier are 

placed in direct connection with 

each other 

— The microphone and speech circuit 

unit are enclosed in a screened 

case 

— Components have been decoupled 

where there is a risk of detecting 

radio signals which, in one way or 

another, could be fed out on the 

line or in to the receiver in the set. 

By these means the set is well protected 

against disturbances resulting 

from detection of radio signals in the 

range 0.15—30 MHz. 

Overvoltage protection 

Electronic circuits in the telephone set 

must be effectively protected against 

two types of overvoltage, namely the 

fairly high transient voltages of short 

duration caused by the exchange 

switching system and also the voltage 

pulses with considerably longer duration 

that are induced across the telephone 

line. 

A conventional zener diode does not 

provide sufficient protection against 

these two types of overvoltages. ERI 

COFON 700 is therefore equipped with 

overvoltage protection in accordance 

with fig. 19. 

Functional characteristics 

DC characteristics 

In order to allocate the subscriber line 

as great a part of the loop resistance 

as possible, conventional carbon microphones 

are made as low-ohmic as 

possible. In such cases the nominal 

d.c. resistance is in the order of 100— 

300 ohms. As the direct currents that 

are necessary for the operation of the 

line relay in telephone exchange systems 

are in the order of 10—20 mA, the 

nominal voltage drop in the carbon microphone 

set has been set to only 

about 4—2 V for long subscriber lines. 

This d.c. loop includes the resistance 

of the carbon microphone. As even 

high quality carbon microphones vary 

slightly depending on their position, 

and as the resistance increases slightly 

with time, the receiving devices in 

the exchange—line relay and impulsing 

relay—are usually dimensioned 

with an adequate safety margin relative 

the nominal voltage drop. 

In the case of electronic sets the limits 

for the d.c. voltage drop across the set 

are very narrow. Furthermore there are 

no position or time-dependent changes 

of the d.c. resistance of the set. Therefore 

it is quite certain that the increase 

in the nominal voltage drop for an 

electronic set, which is necessary for 

the function of the circuits, cannot disturb 

the telephone exchange, even if 

the nominal line current in the case of 

a subscriber line of maximum length 

decreases by some mA. 

In view of the requirements for a 

speech signal that is free from distor-

Fig. 20 

DC characteristics (speech condition) 

ERICOFON 700 

- - - - DIALOG with carbon microphone and dial 


DC characteristics (impulsing condition) 

ERICOFON 700 

- - - - DIALOG with carbon microphone and dial 

Fig. 22 

Reference equivalents rel. NOSFER without 

transmission regulation 

SRE Sending 

WIRE Receiving 

SiRE Sidetone 


Reference equivalents rel. NOSFER with 

automatic transmission regulation 

tion, and the varying speech volume 

used by the subscribers, a distortionfree 

output power of about + 2 dBm 

is required for sending, which corresponds 

to an output voltage of about 

3 V. This requires an amplifier operating 

voltage of about 6 V. 

As polarity protection is also required, 

the lowest d.c. voltage drop across the 

set becomes about 7.5 V, which corresponds 

to a telephone set resistance 

of 350—400 ohms at 20 mA. The direct 

current of the set, as a function of the 

feeding resistance (line resistance and 

current feeding resistance) in the 

speech condition is given in fig. 20, and 

in the decadic impulsing condition in 

fig. 21. For comparison purposes the 

corresponding curves for a conventional 

carbon microphone set (DIA 

LOG) are also given. It can be seen 

that the nominal difference in direct 

current between the two types is very 

small despite the fact that the nominal 

voltage drop across the electronic set 

is higher. 

Transmission characteristics 

As has been mentioned previously, 

ERICOFON 700 is constructed with an 

electronic speech circuit and electret 

microphone. Compared with the conventional 

telephone sets with carbon 

microphone ERICOFON 700 shows a 

number of improvements, such as 

— constant sending sensitivity 

— improved sidetone level 

— improved impedance of the set 

— sending distortion completely eliminated 

— current feeding losses eliminated 

If the transmission characteristics are 

expressed in reference equivalents rel. 

NOSFER it can be seen that the sending 

and receiving characteristics of an 

electronic set have the necessary prerequisites 

for achieving optimum or 

specified values.

Fig. 24 

The impedance ot the telephone set 

and the local line 


Frequency curve for sending 

Fig. 26 

Frequency curve for receiving 


Mean opinion score (MOS) as a function of 

the system reference equivalent (SyRE) 

ERICOFON 700: y = 3.43—0.00133 (x—S) 2 

DIALOG: y = 3.31—0.00175 (x—2.14)' 

For the version without special transmission 

regulation the values shown in 

fig. 22 are those for the reference equivalents 

of the set for sending (SRE), 

receiving (MRE) and sidetone (SiRE). 

With a 0 ohm line SRE is + 3 dB, MRE 

— 4 and SiRE > 10 dB. For the version 

with transmission regulation during 

sending and receiving the values 

shown in fig. 23 are those for sending, 

receiving and sidetone as a function 

of the line resistance, including attenuation, 

with a 0.4 mm subscriber line. 

As can be seen from the figure, in the 

case with transmission regulation the 

efficiency of the telephone set is not 

dependent on type and length of the 

local line. 

The speech transmission circuit is designed 

so that the impedance exhibited 

by ERICOFON 700 is, in the main, 

identical to the impedance of the balance 

circuit. Since the balance circuit 

can match the impedance of the local 

cable very closely, the balance impedance 

has been dimensioned to match 

the line lengths to which the majority 

of the subscribers are connected, 

namely up to about 2 km. This means 

that as regards phase angle and absolute 

value the impedance of the set is 

of the same type and has the same 

value as the impedance of the local 

cable. Seen from the local exchange 

the impedance variations for varying 

line length, including the 0 ohm line, 

are thus very much smaller than in the 

case of conventional sets, fig. 24. 

The frequency curve of the set during 

sending is shown in fig. 25 and during 

receiving in fig. 26. The receiving curve 

is straight and independent of frequency, 

whereas the sending curve rises 

with frequency in order to compensate 

for the attenuation distortion on the 

local line. 

As regards sound reproduction the 

transmission quality of ERICOFON 700 

is considerably better than the quality 

that can be achieved with a carbon 

microphone. 

It is well known that for high quality 

sound reproduction it is necessary to

132 

use a microphone in which the oscillating 

mass is reduced to a minimum. 

The microphone can then be dimensioned 

so that its internal resonance 

lines above the frequency range to be 

reproduced, whereby all pulse distortion 

is eliminated. It is then instead the 

amplifier after the microphone that 

determines the sound quality. The 

mass of the diaphragm in the ERICO 

FON electret microphone is very small, 

the internal resonance is high and lies 

far above the reproduced speech frequency 

band. Hence the electret microphone 

gives an absolutely natural 

speech reproduction. Although it is 

difficult to specify this improvement in 

quality using the present recognized 

methods for characterizing the transmission 

quality of a telephone set, in 

practice the improvement is immediately 

and distinctly noticeable. 

Opinion tests have been carried out in 

order to investigate to what extent subscribers 

notice or benefit from this improvement 

in quality. These tests were 

in the form of conversation tests and 

were carried out with ERICOFON 700 

and DIALOG with carbon microphone. 

During the tests the subscribers held 

conversations over lines with varying 

attenuation and then gave general 

opinions regarding the quality, according 

to a 5-stage scale, where 4 = 

excellent, 3 = good, 2 = satisfactory, 

1 = not very good, 0 = bad. The difference 

in mean opinion score between 

sending from a carbon microphone 

and from ERICOFON 700 indicates 

that, as regards transmission 

quality, a much more positive opinion 

is obtained when using the electronic 

set than when using the carbon microphone. 

With increased line attenuation 

the same mean opinion score was 

obtained for ERICOFON 700 at 6—10 

dB higher line attenuation compared 

with the carbon microphone DIALOG. 

These 6—10 dB can be said to be a 

measure of the value of the improved 

speech transmission quality at the 

same value of the telepohne set's reference 

equivalents rel. NOSFER, fig. 

27. 

Tone ringing 

The standard version of ERICOFON 

700 is equipped with an electronic tone 

ringing circuit. As different telephone 

administrations have different connection 

regulations, the circuit is available 

both in a low-ohmic version for those 

cases where the ringing circuit is disconnected 

when the set is in the transmission 

state, and in a high-ohmic version 

for those cases where the ringing 

circuit is always connected in across 

the line. 

Fig. 28 

Tone ringing. Frequency spectrum

133 

The tone ringing circuit is characterized 

by 

— small dimensions 

— penetrating but still pleasant sound 

—• good sensitivity to the ringing frequency 

20—60 Hz 

— maximum protection against tinkling 

when connected in parallel 

with other dial sets 

— high impedance for speech frequencies. 

Tone ringing has been used in ERI 

COFON for many years. The receiver 

of the set has then been used as the 

sound source. The same principle is 

applied in ERICOFON 700. Compared 

with the previous versions the aim has 

been to achieve a somewhat different 

sound character in the new construction, 

with a greatly increased frequency 

spectrum. The tone consists of a 

pulse-modulated tone frequency signal. 

Fig. 28 shows a long-term mean 

value of the frequency spectrum. As 

can be seen from the sound spectrum 

the signal contains frequency components 

from 700 to 10,000 Hz. This wide 

frequency spectrum provides the same 

possibility of identifying one among 

several telephone sets with tone ringing 

as in the case of the conventional 

bell. Furthermore the lower frequencies 

are of particular importance for 

people with impaired hearing. 

The maximum level of the ringing signal 

is about 80 dB(A) rel. 2X10~ 5 Pa, 

measured at a distance of 1 metre from 

the set. In the standard version the 

level is limited to 70 dB(A). The level 

limiting is provided by a zener diode. 

This limiting has been introduced in 

order to avoid extremely high sound 

levels from the receiver if a ringing 

signal is received when the receiver is 

held up close to the ear with the cradle 

depressed at the same time. This condition 

is extremely unlikely as, unlike 

the two-piece set, the receiver of ERI 

COFON 700 is held far from the ear 

during impulsing. 

Summary 

In the article the construction and 

characteristics of LM Ericsson's first 

electronic telephone set ERICOFON 

700 are presented. ERICOFON is a well 

known product from LM Ericsson with 

good qualities such as low weight, 

comfortable handling, small space requirements 

and excellent transmission 

characteristics. These qualities are also 

to be found in the new product, in 

which all the possibilities offered by 

modern technology have been exploited. 

References 

1. Billing, R.: Keysef for Telephones 

with V.F. Code Signalling. Ericsson 

Rev. 46 (1969): 2, pp. 49—58. 

2. Boeryd, A.: Electronic Telephone 

Sets. Ericsson Rev. 51 (1974): 1, 

pp. 2—12. 

2. Hedman, J. O.: The Electret Microphone 

— a New Microphone 

for Telephony. TELE, English edition 

(XXVIII) 1976, No. 1, pp. 49— 

51. 

4. Gleiss, M: Carbon Microphones 

and Linear Microphones — a 

Comparison. TELE, English edition 

(XXVIII) 1976, No. 1, pp. 41 — 

48.

CCM - A Well- tried and 

Economic Maintenance System 

Verner Eriksson 

An article has been written and is published elsewhere in this number 

to mark the fact that it is now two years since CCM (Controlled Corrective 

Maintenance) was first introduced in the Rotterdam telephone district. 

Thanks to the valuable contributions of the Dutch and other telephone 

administrations in the field of maintenance of telephone exchanges it has been 

possible to further develop CCM to its present high level. The introduction 

of CCM has led to an improvement in the service quality of telephone exchanges, 

at the same time that the maintenance work has been reduced considerably. 

In the following article the author summarizes the CCM method. 

while carrying out their repair work the 

exchange staff unintentionally caused 

more faults, the number of which increased 

with the size of the staff. However, 

this expensive and inefficient 

method of preventive maintenance was 

gradually changed, to a great extent 

due to the rapid development of new 

and more reliable telephone exchange 

systems with facilities for efficient and 

automatic supervision. 

UDC 621.395 722: 

658.581 

LME 154 

Fig. 1 

Operation control room for the Mollison 

international transit exchange in London 

Up to 25 years ago comprehensive preventive 

maintenance work was carried 

out as a general rule in telephone exchanges, 

in an attempt to achieve good 

service quality. This preventive maintenance 

had many disadvantages. For 

example, it was possible to show that 

When the first ARF exchange was installed 

in Helsinki in 1950, the time was 

ripe for studying the maintenance 

question in detail, with a view to replacing 

the increasingly expensive exchange 

staff by automatic supervisory 

equipment. In order to increase the 

scope and depth of these studies, in 

1956 LM Ericsson invited the Nordic

135 

VERNER ERIKSSON 

Telephone Exchange Division 


telecommunications administrations to 

the first maintenance conference in 

Stockholm. During a corresponding 

conference in 1957, the Swedish Telecommunications 

Administration reported 

that they achieved a better quality 

of service, with reduced maintenance, 

in their AGF type of 500-line 

selector exchanges since they introduced 

the basic CCM principles. 

When should maintenance 

measures be taken 

As has been said earlier, it has been 

shown that it is uneconomic to repair 

all faults as soon as they occur, and 

maintenance measures should not be 

resorted to until the service quality 

tends to fall below the level that the 

subscribers have a right to expect. 

How is it then possible to determine 

when maintenance action should be 

taken The economic situation of a 

telecommunications administration is 

made clear by the book-keeping. The 

technical management of the administration 

has every reason to keep corresponding 

»books» for different forms 

of service statistics. From these it is 

possible to determine the quality of the 

service that the subscribers receive, 

which in the long run gives the fault 

trend. Moreover, in order to supervise 

the function of telephone exchanges 

continuously, it is necessary to introduce 

supervisory equipment that works 

on a statistical basis. Modern exchanges 

contain such equipment, 

which in the main supervises only the 

function of the exchange itself. Consequently, 

it is often necessary to supplement 

this with autonomous equipment, 

primarily an automatic traffic 

route tester, TRT. This is an invaluable 

aid, which makes possible an efficient 

CCM. The traffic route tester has been 

described in an earlier issue of Ericsson 

Review 1 . 

Important principles 

In order to achieve the best possible 

result the following main principles 

should be observed. 

IZ Do not interfere with the equipment 

more than is absolutely necessary. 

Fig. 2 a 

Example of how a modern electronic traffic 

route tester can be used in a network 

TRTM Central and controlling unit, which 

Initiates all test connections. It also 

registers the correctness, transmission 

level and tariff Impulse functions etc. 

for each test connection 

TRTS Combined terminating and traffic 

generating unit, controlled by TRTM 

CA Terminating unit 

OMC "Operation and maintenance centre 

Group switching centre 

® Subordinate exchange 

9 Terminal exchange

136 

] Do not allow more staff in the exchange 

premises than is absolutely 

necessary, and keep the premises 

closed and free from dust to the 

greatest possible extent. 

• Give the maintenance staff the necessary 

supervisory equipment, 

with the possibility of supervising 

the service quality outside the exchange 

premises. 

• Take no action before the supervisory 

equipment indicates that the 

service quality has fallen below a 

certain permissible value. 

• Train the staff so that they are able 

to quickly localize and correct 

faults on the basis of the information 

obtained. 

Successive introduction 

of CCM in various countries 

CCM is applied nowadays to a greater 

or lesser extent by all the LM Ericsson 

customers. Some examples are given 

below. 

In order to further develop the ideas 

that were put forward at the 1956 Maintenance 

Conference, during autumn of 

the same year the design of control 

rooms for the ARF exchanges in Alborg 

and Odense were discussed with 

the respective Danish Telecommunications 

Administrations, FKT and 

JTAS. As a result a control room was 

taken into service in Alborg the following 

year, and in Odense at the beginning 

of 1959. 

That the right solution was chosen 

from the very beginning is borne out 

by the fact that the supervisory equipment 

in the Odense exchange still 

functions in accordance with the principles 

that were laid down 20 years 

ago. 

In Australia the first crossbar switch 

exchange from LM Ericsson was installed 

during 1962. In connection with 

this the Administration then introduced 

CCM, under the name Qualitative Maintenance 

2 . Since then the Australian Administration 

has gone even further than 

what is included in normal CCM, and 

have developed their own supervisory 

equipment 3 . As an example may be 

mentioned ADR (Automatic Disturbance 

Recording equipment). With this 

equipment it is possible, among other 

things, to transmit to a supervising centre, 

information concerning faults detected 

by the register control set RKR 

and the state of important marker relays. 

In this way experts stationed at the 

supervisory centres can help the local 

maintenance staff to analyze the 

causes of faults. 

CCM was introduced in Holland in 

April 1966 in the Dordrecht and Zwijndrecht 

areas with very good results. 

The separate article mentioned in the 

introduction makes clear how, since 

then, CCM has so successfully spread 

over the whole of Holland. 

Results achieved 

Experience has shown that the administrations 

that have applied the above- 

Example of some different combinations of 

test connections 

— Control circuit for routing the test 

connections 

—— Connection on test, connected to TRTM 

either direct or via TRTS

137 

Table 1 

Budgeted maintenance contributions for 

the AR system of JTAS in Denmark 

System 

Hours/subscriber line or trunk line 

1970 1971 1972 1973 

Local exchange system with crossbar exchange type ARF 

Rural exchange system with crossbar exchange type ARK 

Transit exchange system with crossbar exchange type ARM 

0.35 

0.33 

5.0 

0.30 0.26 0.28 

0.28 0.25 0.22 

4.20 3.20 2.80 

mentioned principles for their crossbar 

exchanges or similar types of exchanges, 

have been able to successively 

improve the service quality and 

to reduce their maintenance staff. 

As early as 1956, at the first Maintenance 

Conference, LM Ericsson expressed 

the opinion that the maintenance 

work for a normally maintained 

ARF exchange should not exceed 0.3 

hours per subscriber line and year, 

with an operational reliability such that 

the fault rate does not exceed 0.1 % 4 . 

Certain administrations have achieved 

very much better results and others 

are on the way to doing this. An example 

of this is presented in the article 

from Holland. It may also be mentioned 

that an article by B. J. Carrol, 

Australia, contains a statement to the 

effect that: "It is the opinion of the 

author that terminal exchanges equipped 

for 10,000 lines can be maintained 

satisfactorily by one man" 3 , which corresponds 

to a maintenance contribution 

per line and year that is only one 

half of the standardized value of 0.3. 

JTAS in Denmark have reported figures 

for the maintenance of AR type of 

exchanges. It is interesting to note the 

reduction from year to year for the different 

systems, table 1. 

The crossbar exchanges of type AR 

have been in operation, with good results, 

for over 25 years. In no case has 

it been shown that the maintenance 

required has increased as the equipment 

becomes older. However, in certain 

cases there may be good reason 

for thoroughly investigating common 

relay equipment, such as markers, after 

10 to 15 years in service, since these 

are so few in numbers yet of such vital 

importance for the correct operation 

of the whole exchange. This does not 

in any way detract from the substantial 

advantages that are gained with CCM. 

References 

1. Broby, S.-B.: Electronic Traffic 

Route Tester TRT m 70. Ericsson 

Rev. 51 (1974): 3, pp. 80—87. 

2. Moot, G.: The Effect of Human 

Factors on some Aspects of 

Australian Post Office Maintenance 

Operations. Maintenance 

Conference 1974. 

3. Carrol, B. J.: Maintenance and 

Performance of LM Ericsson 

Crossbar Switching Equipment in 

Australia. Part 1 and 2. The Telecommunication 

Journal of Australia 

1973, pp. 72—77, 143—149. 

4. Hansson, K. G.: Maintenance 

Conferences at LM Ericson. Ericsson 

Rev. 52 (1975): 1, pp. 2—13.

Ten Years Experience of CCM 

in the Dutch Telephone Network 

J. A. Harriers and C. Scheurwater 

In April this year, exactly ten years have passed since CCM (Controlled 

Corrective Maintenance) was introduced into the Dutch network, to be precise 

in Rotterdam. Two articles dealing with experiences from this were 

published in this journal during 1968 1 and 1972 2 . Since then, this maintenance 

system has been further developed and large-scale introduction of an 

electronic traffic route tester will take place throughout the country. 

In this article the authors will give a survey of the introduction of CCM in 

the Netherlands and of the results obtained. 

UDC 621.395.722: 

658.581 

LME 154 

The activities necessary for maintenance 

and supervision of automatic 

telephone exchanges depend to a 

great extent on the service quality that 

it is considered economically justifiable 

to offer the subscribers. 

Based on data obtained locally and 

from abroad the conclusion was reached 

already at an early date, that it was 

unnecessary to test the exchanges 

periodically, which on the contrary 

could cause additional faults. Therefore 

in 1957 the Central Telephone 

Branch introduced new instructions, 

which were based on visual inspection. 

The equipment was selected on a 

random sampling basis and checked 

by an experienced technical staff. Thus 

it was indicated in which part of the 

telephone plant irregularities were occuring. 

Measures were then taken to 

remove these irregularities and as 

much as possible prevent that they 

were repeated. 

Special attention was of course also 

paid to faults reported by the subscribers 

as this is of utmost importance 

to enable the administration to offer a 

good service quality. The knowledge 

thus gained has resulted in decreased 

maintenance efforts and improved 

service quality. 

Statistical methods using data from the 

traffic route tester TRT have also been 

introduced. 

As mentioned above pure CCM was 

consequently introduced in Rotterdam 

in 1966. The main principle of this 

method implies that maintenance 

should conform to the required functional 

quality of the exchange. The 

switchroom should be entered only 

when the quality determining equipment 

indicates the right time for this 

or when complaints have come from 

subscribers. However, older types of 

Fig. 1 

General maintenance organization tor 

telephone exchanges in the Netherlands

J. A. HAMERS 

Maintenance 

Manager 

Telephone District ot Rotterdam 

C. SCHEUERWATER 

Chief Division Maintenance and 

Quality Control, Public Telephone 

Exchanges 

Central Telephone Branche 

Netherlands Postal and Communication 

Services 

Table 1 

Development of the service quality 

in the Rotterdam network 

exchanges require preventive maintenance 

to a certain extent, in such 

cases CCM cannot be fully utilized but 

the result has still been good. 

Number of multiple positions up to 31st December 

Number of lines in operation up to 31st December 

Degree of use 

Number of faults reported by subscribers 

Real faults 

Real faults as a percentage of the reported faults 

Number of real faults per line in operation 

Number of real faults In: 

a) Telephone exchanges 

Percentage of the total number of real faults 

b) Subscriber line network 


c) Telephone sets (incl those connected to PABX) 


d) PABX 

Percentage ot the total number of real faults 

Number of real faults in exchanges per line in operation 

For the supervision of exchanges certain 

exchange types include fixed supervisory 

equipment, which sounds an 

alarm when the fault frequency ex- 

Fig. 2 

Technical districts in the Netherlands 

113 controlling and 738 terminating traffic route 

tester units are to be gradually introduced 

First figure means the number of controlling 

traffic route testers (TRTM). 

Second figure means the number of terminating 

traffic route testers (TRTS). 

^ — Boundary of technical districts

140 

Table 2 

Existing staff requirements to different types 

of exchanges 

Crossbar exchanges ARF 10, 6 A 

Crossbar exchanges ARF 10, 6 B 

Crossbar exchanges ARF 10, 8 C 

500-llne selector exchange AGF with relay control 

Crossbar rural exchanges ARK 

Crossbar transit exchanges ARM 20 

Per 10,000 lines 

1.07 man 

1.22 man 

1.45 man 

2.17 man 

3.55 man 

1.98 per 1000 incoming lines 

ceeds the permitted level. Various 

types of traffic testers are also used. 

Improved service quality 

The use of TRT makes it possible to 

find out how the subscribers feel the 

service quality in the network. 

The table 1 gives an idea of the development 

of the service quality in the 

Rotterdam network after the introduction 

of CCM. 

The following two interesting facts appear 

from the figures of the table 1. 

1. The faults in the telephone exchanges 

during 1973 and 1975 

amounted to 3.1 % and 2.3 % of the 

total number of real faults reported 

by the subscriber. 

2. The faults reported by the subscribers 

in the telephone exchanges 

per line in operation decreased 

from 1969 to 1975 by 70 %. 

Staff requirements 

Earlier the staff requirements were 

based on certain norms for the equipment 

concerned. In 1975 the base of 

the calculation was changed to regression 

analysis and an improvement factor 

of 2 % per year will also be applied 

in the future. For 1975 this gives the 

following maintenance requirements 

including chiefs but excluding MDF 

work, table 2. 

The general maintenance organization 

used in the Netherlands is shown in 

fig. 1. 

Electronic traffic route tester 

Traffic route testers are a condition for 

the use of CCM and have been used in 

the Netherlands since 1961. Since 

then, they have been gradually improved. 

On the basis of the needs of 

the Dutch telephone administration 

and technical discussions with this 

administration, LM Ericsson have designed 

an electronic traffic route tes- 

Fig. 3 a 

Increase of local and incoming transit lines 

in the Netherlands 

— Local lines 

___ Transit lines

141 

ter, TRT m70. It is planned to be gradually 

introduced into all parts of the 

Netherlands with 113 controlling and 

738 terminating units in accordance 

with fig. 2. 

TRT m70 is programmed from an electric 

typewriter or loading tape. The 

testing can be very extensive and suitable 

phases can be repeated every 

twenty-four hours. The programming 

period is a maximum of 99 days and 

during this time the daily program may 

vary as required. 

The phases during one day may include 

various tests for the investigation 

of the service quality. Additional 

tests may also be made for charging 

and careful check of the transmission 

level. 

The processed results are written on a 

typewriter, which can be remotely connected 

through a fixed modem connection. 

As a great many test numbers can 

be programmed a comprehensive and 

effective test program can always be 

prepared. 

Number of lines, maintenance efforts 

and fault rate 

The development of the number of 

local and incoming transit lines in the 

Netherlands is shown in fig. 3 a. The 

prognosed maintenance staff requirements 

in case of preventive maintenance 

compared with CCM are shown 

in fig. 3 b which figure also illustrates 

how the fault rate gradually has decreased. 

References 

1. Harriers, J. A.: The Introduction 

of a New Maintenance Method 

into the Telephone Area of Rotterdam 

and its Influence on the 

Maintenance Organization. Ericsson. 

Rev. 45 (1968): 2 pp. 46—60. 

2. Hamers, J. A.: Six Years of controlled 

Corrective Maintenance 

(CCM) in the Rotterdam Telephone 

District. Ericsson Rev. 49 

(1972) pp. 74—85. 

Fig. 3 b 

Comparison between staff required for pure 

preventive maintenance and for CCM with a 

yearly increase in accordance with fig. 3 a 

1. 1966 CCM was introduced in Rotterdam 

2. 1969 TRT in combination with CCM was 

introduced throughout the Netherlands 

The blue curve is only valid for the Rotterdam 

district

Optimization of Power Supply 

Equipment for Modern 

Telecommunication Systems 

Christer Boije af Gennas 

The extensive use of semiconductor components in modern telecommunication 

systems has resulted in an ever increasing part of the telecommunication 

equipment being supplied with power via DC/DC converters mounted in the 

equipment racks. This means that the power supply plant, unlike the earlier 

type which consisted of a clearly defined central equipment, now comprises not 

only a central part but also a distribution part and integrated power units 

mounted in the racks of the telecommunication equipment. 

The article deals with the studies that have been carried out by LM Ericsson 

concerning alternative system solutions for power supply, and describes 

an optimization process in which the costs and performance of the rack 

converters and the distribution material are also included as parameters. 

The article also describes an example in which the optimization method has 

been applied for a power supply plant that supplies a computer-controlled 

telecommunication equipment having typical power supply data. 

Moreover sectioning of the power supply plants is presented as a means 

of limiting the cost of the distribution cabling in the case of large telecommunication 

plants that extend over a large area. 

UDC 621.311.4: 

621.39 

LME 781 

General considerations 

The construction of modern telecommunication 

systems differs quite considerably 

from that of older systems. 

This naturally affects the design of the 

power supply for these systems. 

From the point of view of power, some 

of the most important development 

trends in modern telecommunication 

plants are that 

— electromechanical components are 

to a great extent being replaced by 

semiconductor electronics. 

— telecommunication systems are 

being computerized more and 

more, SPC (Stored Program Control) 

systems. 

— very large exchanges with high 

power consumption have become 

more usual, for example transit exchanges 

with very high traffic 

handling capacity. 

— larger telecommunication exchanges 

often means that power 

has to be distributed over long distances 

in such exchanges. This applies 

particularly if, for space reasons, 

they have been divided up on 

a number of different floors in the 

building. 

Increased electronics factor 

Electronic circuits require to be fed 

with other and more constant voltage 

levels than the electromechanical 

components. Consequently, because 

of the voltage drop and interference 

risks, it is not a good solution to distribute 

these voltages from the central 

power supply plant. 

Hence it is necessary to convert the 

distributed system voltage to voltages 

suitable for feeding the electronic, 

power-consuming units. This conversion 

is usually carried out in what are 

known as rack power units, i.e. DC/DC 

converters placed in the telecommunication 

equipment racks close to the 

units they are to provide with power. 

However, to a greater or lesser degree, 

modern exchanges still contain units 

supplied directly from a suitably selected 

system voltage. 

The ratio between the power that is 

distributed via the rack converters and 

the total distributed power is usually 

Fig. 1 

The electronics factor a is the ratio between 

the power distributed via the rack converters 

and the total distributed power

43 

Fig. 2 

CHRISTER BOIJE AF GENNAS 

Power Supply Department 


A comprehensive knowledge of the whole 

power supply system is necessary in order to 

be able to effect an optimization 

called the electronics factor for the exchange, 

see fig. 1. As is clear from 

what has been said above the electronics 

factor for modern telecommunication 

systems is appreciably higher 

than for older systems. 

More stringent requirements on the 

quality of the supply voltages 

The introduction of SPC systems has 

led to an increase of requirements on 

voltage accuracy as well as freedom 

from transient overvoltages and undervoltages 

in the power supply. 

Undervoltages which are of such short 

duration that they are completely imperceptible 

in electromechanical systems 

can cause disturbances in SPC 

systems through the loss of stored information. 

Such short duration transient 

voltage deviations occur, for 

example, as a result of a short circuit 

and the consequent fuse blowing in 

the distribution network. In the LM 

Ericsson system this disturbance risk 

is prevented by feeding the power consuming 

units individually, direct from 

the central power plant via cables with 

suitably chosen resistance. 

This individual feeding is a characteristic 

of the distribution system that is 

usually called high-ohmic distribution, 

and which has been standardized by 

LM Ericsson for feeding SPC systems. 

The method has been described in an 

earlier number of this publication.' 

Total optimization of power 

supply plants 

When designing a power supply system 

for modern telecommunication 

plants the whole system must be taken 

into consideration when optimizing, 

that is to say the rack converters and 

distribution material as well as the central 

power plant. For example, minimization 

of only the cost of the central 

power equipment can often result in 

increased costs for other parts of the 

plant, and probably does not give the 

lowest total cost for the whole power 

supply plant. 

Thus an optimization process demands 

a very good overall knowledge of the 

parts included in the power supply 

equipment, from the incoming mains 

supply to the power consuming units 

in the racks of the telecommunication 

equipment, fig. 2. 

The following optimization parameters 

must be considered: 

• Equipment performance requirements. 

Towards the telecommunication 

equipment these are fixed 

by detailed specifications. On the 

other hand the internal performance 

requirements (voltage levels, 

tolerances etc.) within the power 

supply equipment can be varied. 

For example, it should be possible 

to compensate a reduced regulation 

capability in the central power 

units by an increase in the regulation 

range of the rack converters.

144 

Initial expenditure. This consists of 

the acquisition costs for the units 

and other equipment included in 

the power supply system together 

with the installation costs. 

Operational costs are influenced by 

the efficiency of the system and the 

need for maintenance measures. 

Reliability. In modern telecommunication 

systems it is a particularly 

rigorous requirement that sufficient 

feeding power is always available. 

This requirement is satisfied in the 

power supply system, the risk of 

system failure being minimized by 

the introduction of standby units 

(redundancy) and grouping into cut 

out units. 

Safety aspects must be taken into 

consideration when selecting the 

system voltage. The cost of protective 

covers and guards, improved 

insulation and adaptation of the 

system to varying national and international 

safety regulations must 

all be considered. 

Future power plants 

Goal 

The optimum design for future power 

plants has long been studied by LM 

Ericsson. 

Thegoal has been,among other things, 

to 

— find alternative methods for the 

power supply of future telephone 

systems 

— give methods for how alternatives 

can be compared from the viewpoints 

of costs and function 

— determine, with the aid of cost relations 

and prognoses, the solutions 

that are favourable (optimization), 

i.e. find suitable voltages and 

give relative costs for different degrees 

of centralisation of the power 

supply equipment. 

The studies have been concentrated 

mainly on the choice of the system 

voltage and the current type for feeding 

telephone exchanges of the future. 

In addition the question has been considered 

as to how the regulation functions 

should be allocated; decentralized 

regulation in the vicinity of the load 

or centralized regulation in the central 

power supply plant, see fig. 3. 

Model exchanges 

During the course of the studies cost 

relationships have been established 

which are universally valid, and these 

have been applied for different model 

exchanges, representing the various 

LM Ericsson SPC systems. Thus both 

AKE and AXE systems have been dealt 

with. 

Alternative solutions 

For more than a decade the present 

LM Ericson power supply system has 

proved to be economical, reliable and 

adaptable to varying system requirements. 

The system is characterized by a 48 V 

system voltage and booster converters 

2 . The following alternative solu- 

Fig. 3 

Centrally regulated power supply system. 

The distribution voltage is maintained constant 

by means of regulated booster converters 

Rack converters

145 

tions have been studied with this system 

as a reference. 

1. Distribution of a.c. voltage, 1-phase 

or 3-phase, at the mains frequency. 

2. Distribution of a.c. voltage at higher 

frequency. 

3. DC voltage distribution with decentralized 

regulation. Dispensing with 

the booster converters and feeding 

all the load via DC/DC converters 

with increased regulation range. 

4. DC voltage distribution 

a) System voltage of 140 V 

b) System voltage higher than 140V 

Distribution of a.c. voltage means 

more expensive standby energy 

The advantage of this alternative is 

that it is very easy to transform a.c. 

voltages to other voltage values. At the 

same time relatively simple rack rectifiers 

can be used as the local rack 

power units instead of DC/DC converters. 

However, as has been pointed out 

earlier, a modern telecommunication 

system demands a power supply that 

is completely free of interruptions. 

This means that the system requires 

instantaneous access to standby energy 

in the case of an interruption of the 

regular energy sources. 

The studies have shown that the most 

economic and reliable form of energy 

storage, which at the same time satisfies 

the above requirements, consists 

of some form of modernized variant of 

the conventional lead-acid accumulator. 

Since the storage battery operates at 

d.c, charging rectifiers are also needed 

in a system with a.c. voltage distribution, 

as well as DC/AC inverters 

for converting the standby energy. The 

latter means that the size of the battery 

must be greater than in the d.c. system 

in order to compensate for the efficiency 

loss. Moreover an extra cost for the 

inverter must be taken into account. 

As a result of these disadvantages and 

other considerations it has been decided 

that a.c. voltage distribution is 

unsuitable for feeding the telephone 

exchanges of the future. 

Decentralized regulation is expensive 

The battery voltage varies over a wide 

range with different operating conditions 

(charging, discharging). The use 

of booster converters constitutes one 

possible method of providing primary 

regulation of the distribution voltage. 

Dispensing with this regulation possibility 

would mean that the regulation 

range of the rack converters would 

have to be increased. Thus they would 

have to be able to provide the full output 

voltage for a very much lower input 

voltage, see fig. 4. 

Calculations on a number of types of 

rack converters show that this in- 

Fig. 4 

System with decentralized regulation function. 

Variations in the distribution voltage are 

compensated by rack power units with a larger 

input voltage range and by feeding the 

remaining load via regulated direct converters

Table 1 

Acquisition costs for different designs of 

complete power supply equipment for a large 

telephone exchange ol the SPC type. 

The power consumption ol the exchange is 

250 kW, the electronics factor 60 "h and the mean 

distribution distance 45 m. The costs are 

related to the cost of a 48 V booster converter 

system 

Fig. 5 

Plant cost as a function of the electronics 

factor. The plant data, apart from the 

electronics factor, are given in the text of 

table 1. The cost is related to a 48 V booster 

converter system with 60 °/o electronics factor 

A higher electronics factor reduces the additional 

outlay for direct converters. However, more 

expensive rack converters (greater regulation 

range) means that even with an electronics factor 

of 100 Vo the 140 V plant is still more expensive 

than the equivalent 48 V booster converter plant 

46 V booster converter system 

= = 140 V system 

% Relative plant cost 

creased regulation range would, on 

average, increase the cost of the converters 

by about 15%. Regulation of 

the distribution voltage with DC/DC 

booster converters is carried out centrally 

and using units with relatively 

high power. This gives a low cost per 

watt output power. To this must be 

added the fact that the principle of 

booster converters is particularly economical 

owing to the fact that only 

about 20% of the total power passes 

the main circuit of the converters. 

Calculations have shown that with 

booster converters the regulation cost 

per watt is between 5 % and 8 % of 

the cost per watt for small rack converters. 

If this cost is compared with the additional 

cost (15%) of an increased regulation 

range for the rack converters, 

it is clear that central regulation of the 

system voltage using DC/DC booster 

converters is definitely economically 

advantageous. 

Higher system voltage 

An analysis of the characteristics of a 

power supply system with a system 

voltage in the range MOV to 300V 

shows that there are essentially two 

kinds of advantages with such a system: 

1. As a result of the higher voltage the 

current in the distribution cables is 

reduced for a certain distributed 

power. Thus smaller distribution 

cables can be used with higher 

voltages. 

2. It is only to a very small extent that 

the system voltage can be used for 

direct feeding of the power consuming 

units. Thus practically all 

the power must pass through (regulated) 

converters before it reaches 

the units that consume it. This 

means that larger battery voltage 

variations can be permitted than in 

the case of, for example, the full 

float system or the cell switching 

100 % system. Thus the batteries can be 

Electronics factor utilized better since they can be 

discharged to a lower level when 

there is a mains failure. A considerable 

reduction in the size of the 

battery can be achieved in this way. 

The cost of the rectifiers will also 

be reduced to some extent since, 

among other things, the end cell 

rectifier will not be required. 

As can be seen, the cost reductions in 

point 2 are not actually caused by the 

increased system voltage, but rather 

by the introduction of an efficient regulation 

of the system voltage during 

emergency operation. The same advantages 

are of course obtained with, 

for example, a booster converter system. 

Cost comparison for different 

power supply systems 

The relative costs for some different 

designs of a power supply plant for a 

telephone exchange of the SPC type 

are shown in table 1. As an example a 

large exchange with a power consumption 

of 250 kW has been chosen. The 

electronics factor is 60% and the 

mean length of the distribution cables 

is 45 metres. These values are typical 

for exchanges of this type and size. 

Battery saving possible both in 48 V 

and 140 V systems 

It can be seen from table 1 that the battery 

costs are considerably higher in 

the cell switching system than in the 

other alternatives. 2 There is, however, 

no difference between the remaining 

alternatives in this respect, which illustrates 

the above mentioned argument 

that, from the point of view of the battery, 

it is unimportant whether the 

voltage regulation of the distributed 

power takes place centrally, using 

booster converters or locally, using 

rack converters and direct converters 

for 140/48 V. 

For the 140 V system direct converters 

are also required 

In the 140 V system the costs for boost^r 

fi^nuortorp lit/ill r\f rnnroo ho cayoH

147 

Fig. 6 

0 50 100 % 

Electronics factor 

System efficiency as a function of the 

electronics factor. Losses in the central power 

plant, distribution cables, rack converters 

and direct converters (in the 140 V system) 

are included 

!r^^= 

48 V booster converter system 

140 V system 

In order to reduce the cost of the distribution 

cable at the higher system voltage, a voltage 

drop is normally allowed in the conductors which 

is proportional to the distribution voltage. 

This means a constant power loss in the 

distribution cables for a certain given system 

power, irrespective of the system voltage. 

To this must be added the efficiency losses in 

converters. 

From the above it is clear that a higher system 

voltage does not necessarily result in reduced 

power losses in the system. 

Calculations, which for space reasons are not 

given in this article, show that a 48 V booster 

converter system has lower power losses with low 

and medium values of the system electronics 

factor, whereas for higher values (,< > 85 °/o) 

the system efficiency is higher with the 

140 V system 

but on the other hand the rack power 

units will cost more because they must 

then accept larger variations in input 

voltage. Moreover, to these extra costs 

must be added the costs for direct converters, 

140/48 V, for that part of the exchange 

power consumption which in a 

48 V system can be fed direct at the 

system voltage, but which in the 140 V 

system must be fed via converters. 

The result is that the 140 V system certainly 

does have a cheaper central 

part, but on the other hand the local 

part, with rack power units and direct 

converters, is more expensive, see 

fig. 5. 

Cable costs are lower 

in the 140 V system 

The lower distribution current required 

in the 140 V system results in a considerable 

reduction in costs for the 

distribution cabling compared with the 

48 V system. Table 1 refers to a case 

with a mean distribution distance of 

45 metres. This is a realistic value for 

most exchanges of this size. However, 

longer distribution distance can be encountered 

in certain special situations. 

For example, it can be a question of 

extremely large exchanges in city centres, 

where the exchange extends over 

several floorsof the exchange building. 

For long distribution distances the 

cable costs increase more rapidly in 

the 48 V system than in the 140 V system. 

It must be pointed out, however, 

that there are other ways than increasing 

the distribution voliage for keeping 

down the cable costs in the case of 

telecommunication exchanges extending 

over a large area. See the section 

that follows, which deals with sectionalizing. 

Increasing the system voltage above 

140 V does not affect the cable costs 

In most cases an increase in the system 

voltage above 140 V does not result 

in any appreciable reduction in 

cable costs. This is because the crosssectional 

areas of the cables used at 

140 V cannot be reduced further for 

reasons of strength. 

Fig. 7 

Cost of a distribution cable as a function of 

the distribution distance. The cost is related 

to the total cost of the booster converter 

system in accordance with table 1 

By sectionalizing the 48 V plant the mean cable 

length can be limited to between 20 and 30 m, 

which means that at a distribution distance of 

about 80 m the cable costs for this plant will 

already be lower than those for the equivalent 

140 V plant

148 

Fig. 8 

Instead of feeding the parts of the 

telecommunication plant from a common 

central power plant, sectionalizing makes 

possible feeding from several smaller power 

supply plants. These can be placed near 

the parts of the telecommunication plant that 

are to be fed with power, which results 

in a considerable saving on cables. Voltage 

equality between the different parts of the 

telecommunication plant is maintained by 

means of a master voltage control system 

Sectionalizing of the power 

supply plant 

The contribution of the distribution 

cables to the total cost of the power 

supply plant increases relatively quickly 

when the mean length of the cables 

in the exchange exceeds a certain value. 

One of the reasons for this is that 

above this value the maximum permissible 

voltage drop will be decisive for 

the area of practically all cables. The 

cable costs will then be approximately 

equal to the square of the distribution 

distance, see fig. 7. 

By far the greater number of telecommunication 

exchanges of the SPC type 

have such distribution distances that 

a normal 48 V booster converter system 

will be cheaper than an alternative 

with a higher system voltage, for example 

140 V. However, exchanges that 

extend over very large areas, where 

the cable costs could be decisive, cannot 

be ignored. In such cases LM 

Ericsson apply a method of dividing 

up the power equipment into a number 

of sections, each section supplying 

its own local part of the telecommunication 

equipment. In this way it is possible 

to cut down the distribution distances 

drastically, and hence also the 

cable costs, see fig. 8. 

It is clear from what is said below that, 

apart from improved cable economy 

when distribution distances are long, 

sectionalizing also has other important 

advantages. 

Requirement of voltage equality 

between the sections 

If a large telecommunication plant is

149 

fed from a sectionalized power plant, 

the distribution voltages in the individual 

parts must be held at the same 

value to within very close limits. 

The requirements set by LM Ericsson 

are that the difference between voltages 

in the negative conductor at two 

arbitrarily selected rack fuses must not 

exceed 0.8 V and that the voltage difference 

at two corresponding points in 

the positive conductor must not exceed 

0.6 V. 

Since the major part of this tolerance 

is used to cover the differences in 

voltage drop in the distribution cables, 

the permissible difference between different 

distribution racks constitutes 

only a small fraction of the values 

given above (

150 

Fig. 10 

Apart from a highly stable voltage reference 

and regulation amplifier, the central unit 

for master voltage control contains digital 

voltmeters for precision reading of the 

distribution voltages of all connected plants 

and the voltage differences in relation to each 

other and to the reference voltage 

additional central equipment for master 

voltage control. This central equipment 

continuously measures the difference 

between the distribution voltage 

of each section and a special, 

highly stable reference voltage. If a 

difference is detected, a correction 

signal is sent to the section in question. 

This correction signal affects the regulation 

level of the units in the section 

in such a way that the deviation is eliminated. 

A fault occurring in the central unit or 

in the connectors will not have any 

serious consequences since there is 

an internal limitation of the regulation 

range, whereby the correction signal 

is only able to influence the regulation 

level over a small voltage interval 

(± 1 V approx.). 

Comparison between sectionalized 

and unsectionalized systems 

It can be seen from table 1 that sectionalizing 

reduces the cable costs for 

the exchange in question by just over 

50 %, or about 5 % of the total cost of 

the whole power supply plant. However, 

the cost of the equipment for 

master voltage control must be added. 

This cost is calculated to be in 

the region of a half per cent, so that 

the gain with sectionalizing can be expected 

to be just over 4 % for this exchange. 

For a telecommunication plant distributed 

over a wide area the cable costs 

increase considerably for an unsectionalized 

plant, whereas with a well 

planned sectionalizing these costs can 

be held almost constant. 

Sectionalizing gives great advantages 

The most important advantages to be 

gained by using sectionalized power 

supply for large telecommunication 

plants are given in the following summary: 

1. Sectionalized power equipment 

can be placed nearer the load 

centres. The length of the distribution 

cables is reduced and also 

their cross-sectional area for a 

given permissible voltage drop. 

2. The reliability increases, since any 

operational disturbances in a sectionalized 

power plant will affect 

only a part of the telecommunication 

plant. This applies, for example, 

to transients in connection 

with temporary short circuits in the 

d.c. distribution. 

3. Busbars can be dimensioned for 

less current. The short-circuit 

power is reduced, which lowers the 

mechanical strength requirements 

for busbars etc. 

4. The available space can be utilized 

better when making extensions. It 

is no longer necessary to pay so 

much attention to the distance to 

the older power plant. 

Summary 

The conditions that must be laid down 

for a power supply system for modern 

telecommunication plants can be summarized 

as follows: 

It must be so technically advanced 

that it satisfies with high reliability 

all the technical requirements that 

are made, and are likely to be made 

in the future, by modern telecommunication 

plants. 

_ The system must have good modularity 

in order to facilitate sectiona- 

Ii7inn. nrniininn and pytpn^inns

151 

• A single system voltage should be 

used in order to limit the number 

of variants of the equipment included 

and connected. 

• The system voltage used should be 

such that the cost of adapting to 

national and international safety 

regulations is minimized, while at 

the same time all unnecessary risk 

of injury to the staff must be averted. 

• The system must be more economical 

than comparable alternatives, 

both as regards operation and acquisition 

costs. 

The detailed studies that have been 

carried out by LM Ericsson indicate 

that the above requirements are fulfilled 

best by the LM Ericsson booster 

converter system with a 48 V system 

voltage, and sectionalizing in suitable 

cases. 

It is the intention of LM Ericsson to 

continue to use this system also in the 

future as the standard system for supplying 

the power for modern telecommunication 

plants. 

Cost calculations 

The total acquisition cost per unit of power for a certain power supply plant can be 

written as 

K total = K central" 1 " K cables"*" K local 

s tne cost for tne central 

^central ' power supply plant, which in its turn can be divided 

up as follows: 

A central ~ A battery ~ rectifier booster converter "distribution 

The costs for the exchange distribution cables, ^cab | es , can '- )e described as 

""cables = f ' c '' ' d 

' ^cables 

where d is the mean cable length for the distribution cables in the exchange; tables 

is the cable cost per metre mean cable length. 

f(c/) is a function that describes how much the cable costs per metre increase with 

increased distribution distance, owing to the fact that larger cable cross-sectional 

areas must be used to keep the resistive voltage drop constant. 

The cost of the part of the power supply plant that is placed in the telecommunication 

equipment racks, i.e. rack power units plus any direct converters, can be given 

by means of the following equation: 

""local 

= 

"• ' 

F (J") ' ""rack converters" 1 " ( 1— -°0 ' 

F U") ' 

K direct converters 

where a is the electronics factor for the exchange, which thus gives how large a 

part of the total exchange power is used for feeding rack converters. K rack converters 

is the mean value of the cost per unit of power for the rack converters. 

If the selected system voltage is such that the non-electronic load cannot be fed 

direct with this voltage, direct converters are required for feeding this load. The cost 

per unit of power for these converters has been designated K direct converters- 

Thus the power that has to be conveyed by these converters is given by (1—r

Development, Production and 

Maintenance of Software 

for AKE 13 

Lars-Olof Noren and Siwert Sundstrom 

Transit exchange system AKE 13 and its software have been described 

in earlier articles in Ericsson Review^- 2 , and also methods and support systems 

for testing the software 3 . 

The article gives an insight into the development, market adaptation, production, 

installation and maintenance of the software. It is important for a modern 

telephone exchange system that these activities are organized logically and that 

the system is able to satisfy the various demands made on it. 

signals, and for making and executing 

logic decisions, are realized in programs. 

These are stored in the common 

control store together with data 

concerning the build-up of the exchange 

and network and about the upto-date 

status of the connection sequences. 

The structure and function of 

the programs was described in an 

earlier article 2 . 

UDC 621.395.722: 

658 581 

LME 66 

Transit exchange system AKE 13 is a 

SPC system, fig. 1, that has been developed 

by LM Ericsson. The basic functions 

of the systems are already fully 

developed and in operation, but further 

development of various functions is 

going on all the time. The system is 

adapted to new market requirements 

by the addition of new basic functions, 

and above all in the form of the addition 

of new signalling systems when 

the system is introduced on new markets. 

Since the control logic in a SPC exchange 

is realized mainly in software, 

new development work consists mainly 

of software design. Hence LM Ericsson 

have a staff of software designers 

both in the parent company and the 

subsidiary and associated companies. 

Broadly speaking, the work has been 

allocated so that the designers in the 

parent company program various general 

functions while the subsidiary and 

associated companies program the 

functions that are specific for their 

particular market, for example signalling 

functions. 

Support system APT has been developed 

for the production of software. 

However, the support functions are 

not only used for design and the associated 

testing of new software, but 

also for all subsequent handling of the 

software, comprising production of 

program and data packages for the 

different AKE exchanges and administrations, 

and for the maintenance of 

a comprehensive program library. 

Software and documentation 

In a SPC system all functions for storing 

and interpreting control and state 

In the following description programs 

and data are summarized under the 

concept software. 

The software must obviously be documentated 

just as carefully and well 

organized as the hardware. It has proved 

to be rational to document and 

register software products according 

to the same rules as other articles in 

the LM Ericsson product range. 

The basic unit in the system is called a 

function block or often just block. The 

block contains program sequences 

with functionally associated data and 

hardware units. For example, all program 

sequences and data records that 

are used for signalling in a certain type 

of code receiver, together with the 

code receiver itself, constitute a code 

receiver block. 

Each block is described in a set of 

documents, which are brought together 

in a document summary. The 

medium that is used for a certain document 

can vary depending on where 

the document is used. Thus certain 

documents, forexample program code, 

are stored on magnetic tape, whereas 

others are printed and are available in 

book form, for example operational instructions. 

Like all other products, during its lifetime 

the software undergoes a number 

of changes because of modifications, 

function additions etc. Each time there 

is a change of the block program code 

the block is given a new revision state, 

which is entered in the document 

summary, which also includes information 

regarding which documents have 

been revised. The document summary 

thereby unambiguously defines the 

document set that applies for a certain 

revision state in the block.

153 

LARS-OLOF NOREN 

SIWERT SUNDSTROM 

Telephone Exchange Division 


For a hardware product there are a 

number of types of documents intended 

for different user categories. Certain 

documents are only intended for 

operation etc. 

In the same way some of the software 

documents are intended for inserting 

the block in a program package for a 

certain exchange, while other documents 

are intended for the exchange 

staff who are to use the function in 

operation. Thus the software products 

in the form that they are stored in the 

program library are not complete exchange 

functions, but rather production 

documentation. 

Analogous with the successful philosophy 

that LM Ericsson have applied 

for electro-mechanical crossbar systems, 

the design of the AKE 13 software 

has been based on the following 

requirements'. 

flexible adaptation to different markets 

and exchange requirements 

• successive introduction of functions 

without radical system changes 

introduction, without operational 

disturbances, of function changes 

and extension to exchanges already 

in operation 

• high reliability 

r^ lowest possible costs for development, 

planning, production, installation, 

operation and maintenance 

• division of the handling of the software 

between the Ericsson Group's 

different units and licensees. 

Fig. 1 

Block diagram of the hardware for AKE 13 

Fig. 1 a 

Exchange test position for an AKE exchange 

Software requirements and 

program categories 

These requirements, which in some respects 

are unique for computer applications, 

have been possible to fulfil 

through 

• a general program system structure 

with strictly defined interfaces between 

different function blocks, 

which enables function blocks to be

154 

combined to meet the needs of 

each individual exchange 

] general and easy to use design 

rules and design elements 

development of routines and support 

systems for the handling of 

software 

a functional organization both at 

the parent company and the subsidiary 

companies and with good 

communication between them. 

This is illustrated in the following description 

of the routines for a number of 

different cases of software handling. 

The relation between the different development, 

planning and production 

phases for the software are summarized 

in fig. 2. 

Market-dependent and general blocks 

Thanks to the wide market coverage 

already achieved, the software handling 

nowadays consists more of plan- 

Fig. 2 

Development and application o( the software

155 

ning and production than new design. 

This is perhaps best exemplified by 

the fact that when AKE 13 is to be introduced 

on a new market, it is usually 

only necessary to design 5 to 10 new 

blocks out of the total of 100 to 150 

blocks in the exchange. (The actual 

number of blocks in the exchange varies 

according to its complexity.) Moreover, 

the new blocks can very often be 

obtained by modifying a previously 

designed block. The remaining blocks 

are selected from about 400 existing 

blocks. Of these about 200 are special 

for certain markets, while the remainder 

can be used on a large number of 

markets. 

Despite a planned expansion of new 

(system) functions and new markets 

only a very moderate growth of the 

product assortment is foreseen, and 

the present relationship between market-dependent 

and general blocks is 

likely to be maintained. 

The above confirms that the requirements 

for general application and 

adaptability are fulfilled satisfactorily. 

Standardization also improves the reliability 

of the software. Finally it can 

be said that the efforts that have been 

and are being devoted to handling 

routines, support system and organization 

are more than justified. 

Creation of the program 

package 

The software is delivered in the form 

of separate program packages for 

each exchange, and contains only 

functions that are relevant for the exchange 

in question. Up-to-date exchange 

data for traffic routes, routing 

etc. are added when the package is 

loaded. 

When the exchange is put into service 

aftera comprehensive function change, 

or after a large extension, a complete 

package is provided. For minor 

changes, extensions or function additions 

it is usual to provide only a supplementary 

package. Planning, pro- 

Planning 

O Dimensioning 

o Project spec. 

Exchange assembly 

o Project file 

o Model construction 

O Allocation 

O Evaluation 

Package construction 

O Integration OS 

O Production testing 

O Package documentation 

Fig. 3 

Planning and production of program packages 

APT 

LF 

LT 

OS 

PF 

Switching system 

Library file 

Load tape 

Operating system 

Project file 

Delivery to the 

customer's exchange

156 

duction and putting the package into 

service is described in detail in figs. 

3 and 4. 

Planning 

When carrying out the initial planning 

a list is compiled—the project specification—of 

the exchange software 

functions, expressed in terms of the 

blocks that are applicable for the exchange. 

This is based on the program 

library. If the desired functions cannot 

be realized with existing blocks, the 

design of new blocks is initiated. 

The project specification constitutes 

the input document. The exchange can 

then be dimensioned with the aid of 

this document and the actual traffic 

values. 

Computer-stored block information— 

for example programs in source code 

language—for the blocks included in 

the project specification is transferred 

to the newly formed or existing project 

files for the exchange, with the aid of 

the APS system. Only certain information, 

such as size, references etc., is 

transferred for the standard operating 

system concerned, since this system 

can be used unchanged in all exchanges. 

The APT blocks are then brought together 

in the project file to form larger 

handling blocks—models. An example 

of this is the programs for central handling 

functions, programs stored on peripheral 

media such as magnetic tapes 

etc. Normally, earlier models for other 

exchanges or program packages can 

be utilized directly or after modification, 

in which case they are transferred 

from the program library or from a 

project file. 

The next step is to take out, on the 

basis of the specific relationships for 

theexchange ir question, theexchange 

parameters, i.e. initial data, which can 

be established at the time that the program 

package is generated. An example 

of this is the required sizes of 

various data storage areas, which in 

their turn depend on the size of the exchange. 

Another example is the control 

information for selection of the re- 

Preparation of 

the exchange data 

Production of 

delivery package 

Generation of 

exchange data 

tables and complete 

load tape in 

the customer's 

exchange 

Fig. 4 

The exchange data is added to the program 

package and the resulting software package 

is put into service 

Testing and putting 

into service 

LT 

Load tape

157 

levant subfunctions, from within a 

block that has a larger range of functions 

than what is required for the exchange 

in question. 

Production 

The program package is generated in 

target code form in the project file. 

This means that the programs are 

translated to binary form, and are 

allocated in the available program 

stores, that the data stores are allocated 

and that references between different 

parts are filled in. The completely 

allocated program package is then 

output in a form that can be loaded in 

the AKE 13 system processors, and 

package descriptions are printed on 

line printer lists. A supplementary 

package is always based on the original 

package in the completely allocated 

form just mentioned. 

The support system APS, which is run 

on an IBM/370 computer, is used for 

the activities described above. An 

AKE-system test plant, in principle 

built up in the same way as a normal 

AKE exchange, is utilized for the integration 

with the relevant standard 

operating system that follows, and also 

for production tests of the complete 

program package. The procedure 

which is then applied has been described 

in an earlier article 3 . 

Since the program package is based 

on completely allocated standard 

operating systems, the work involved 

in producing the program packages for 

the different exchanges is considerably 

reduced, at the same time that the 

reliability of the operating systems, 

with their central operation and maintenance 

functions for the control system, 

is very high. In other respects the 

standardized operating systems are 

planned, produced and tested in a similar 

way to the exchange program 

package. 

It is planned that in future the central 

parts of the program package switching 

functions will also be generated 

on the basis of a similar standard 

package. 

The tested and complete program 

package is delivered to the customer 

together with the necessary documentation, 

which apart from the pure package 

describing documents also includes 

product describing documents 

for new or modified blocks. 

Putting into service 

After delivery, the program package 

must be put into service, which is illustrated 

in fig. 4. In parallel with the 

production of the program package 

the telephone administration, in collaboration 

with LM Ericsson, prepare 

the exchange data. Examples of these 

are line categories, route data and 

traffic routing data. These data are 

read into the system together with the 

new program package, after which 

the exchange data tables are generated 

with the aid of special programs included 

in the program package. For a 

new exchange a complete set of exchange 

data is required. For a function 

change or extension, on the other 

hand, it is only necessary to prepare 

and read in the new data, because the 

exchange data generators can then 

utilize the exchange data tables generated 

earlier. 

After this, a load tape is generated 

containing the complete information 

in the data and program stores in binary 

form, and also certain control data 

tables. If necessary, this tape can be 

read back into the system program 

and data stores. 

In connection with the read-in of the 

exchange data and generation of the 

exchange data tables, the generated 

data is successively tested by means 

of validity checks of the input data 

using special test functions and test 

traffic. Any errors that are detected 

are corrected successively, and thus 

the load tape for back-up will contain 

information, the correctness of which 

has been verified as far as possible. 

Finally the program package is taken 

into service. By exploiting the special 

advantages that the synchronous duplicated 

control system offers, this and 

also the generation and testing of the 

exchange data can be carried out in an 

exchange that is already in operation 

without any other disturbances than a 

few and controlled system restarts.

158 

Fig. 5 

Working procedure when producing software 

LF Library file 

DF Design file 

Design prerequisites 

Reliability aspects 

The AKE 13 type of transit exchanges, 

which are placed centrally in the network, 

must be extremely reliable and 

must have high availability. That an 

AKE 13 program package has been 

able to satisfy these requirements is 

mainly because. 

the blocks from which the program 

package is produced have low fault 

rates, i.e. high reliability before 

they are released for general use 

a standard block is utilized for several 

markets and a standard operating 

system is used, which means 

that any remaining design errors 

are detected quicker, and thus the 

reliability of the system increases 

at a faster rate 

the restart functions that are included 

in the software limit the effect 

of any errors that may remain 

the computer-based support system 

APS, which is used for production 

and testing of the program 

package, limits the amount of manual 

work that is required and hence 

the risk of faults 

the functions included in the software, 

which generate the exchange 

data and which are used for testing 

a new program package before it 

is put into service, limit the manual 

work, with a consequent reduction 

in the possibility of faults, and detect 

faults before they have any 

serious effect 

comprehensive, successive manual 

checks and computer supported 

testing is carried out while the program 

package is being produced 

and put into service. 

Block description 

Programming 

Design verification 

Release for general use 

Design of new software 

Limited new product range 

As has been shown in fig. 2, new program 

blocks are designed either when 

a system is to be provided with additional 

functions to meet new requirements 

or when a certain market has 

special requirements that the system 

has not previously encountered, for 

example signalling systems that are 

unique for that particular market. 

These new blocks can very often be 

designed as modifications to previously 

designed blocks, which they replace 

entirely. In this way the range of products 

can be kept down. Furthermore, 

when modifying blocks in this way it 

is often possible to improve the block 

characteristics such as storage capacity, 

real-time requirements and reliability. 

By exploiting the experience gained 

from earlier, well tried system solutions 

and general design elements, together 

with established design rules 

and working methods, the program 

designers can to the greatest possible 

extent confine themselves to the 

switchina Droblems.

159 

Block design and transfer to 

the program library file 

The working procedure when designing 

the software is summarized in fig. 

5. Various parts of the APS system are 

used as support in connection with this 

design work. 

After the required functions have been 

divided up between the hardware and 

software parts of the block, the internal 

function sequence is designed with the 

aid of a block flow chart. At the same 

time the specific data storage areas 

for the block are designed and the program 

logic is allocated to the different 

priority levels. Furthermore, the required 

number of state variable is determined 

and also their allocation. Finally 

an accurate description is prepared 

of the block functions and characteristics. 

When designing block flow 

charts the flow chart drawing facilities 

of the APS system are exploited. Relevant 

information is stored in a design 

file, which is utilized throughout the 

remainder of the design work. 

Before the detailed program design 

work is started, the different designers 

cooperate in order to check the function 

and design of the block against 

the set requirements and design practice. 

A check is then also made of the 

real-time requirement and storage volume 

of the block, which at this stage 

can be foreseen with a high degree of 

certainty. 

In the next phase the program logic in 

the block is designed in source code 

form. For this purpose design elements, 

for example are utilized which 

are automatically fetched from the 

program library in connection with the 

compilation. Apart from the format 

checks, which are performed by the 

APS system, a manual check of the 

code is made before the block is verified. 

After one part of the block is designed, 

it is verified by testing. Other completed 

parts are then tested, both separately 

and together with the other parts 

that have already been tested. This 

continues until the whole block has 

been tested in an environment which 

is as realistic as possible. A detailed 

description of the testing procedure 

has been given in an earlier article in 

Ericsson Review 3 . 

The source program listings and other 

documents, which describe the product 

and its application, are now added 

to the block description and block 

flow chart, in which all design changes 

have been entered. These block documents 

are then transferred to a document 

library file, from where they can 

be distributed to the users. At the same 

time all computer-stored block information 

is transferred to a program 

library file. The block is then available 

for general use, and a message to this 

effect is sent to all potential users. 

Coordination at the parent company 

In order to achieve designs that are of 

high quality throughout and to avoid a 

duplication of work in the dispersed 

design activities, the coordination of 

program designs and development of 

design elements, support systems, design 

rules and work methods has been 

centralized to the parent company in 

Stockholm. That this central coordination 

activity functions efficiently and 

well is perhaps just as necessary as, 

for example, good program system 

architecture, if it is to be possible to 

achieve the previously mentioned 

goals for the AKE 13 software. 

Handling of design errors 

Despite the most rigorous testing routines 

during the development of the 

software, there is still a risk that there 

will be certain design weaknesses or 

design errors when newly designed 

blocks are taken into service. Consequently 

the program system has been 

provided with a number of functions 

for the detection of such errors, in order 

to limit their consequences and to 

simplify their correction. 

When an error is detected in a block 

that has been released for general use, 

which may occur during the installation 

or when the exchange is in operation, 

an error message is prepared. If 

the error results in serious operational 

disturbances a preliminary program 

correction is made at the same time, 

which temporarily neutralizes the fault. 

The form that this takes is also given 

in the error message.

160 

The error message is sent from the exchange 

to the fault centre of the organization 

that supplied the program 

package. From here the message is 

distributed to the responsible design 

authority (design holder), who designs 

and tests the final program change. In 

this case also, the designer works on 

the previously mentioned design file. 

The change, together with a number 

of previously accumulated changes 

and changes carried out later on the 

block in question, will eventually result 

in a revision of the block. This is stored 

in the library file as a new, general issue 

of the block in a similar way to that 

described by means of fig. 5. As quite 

a long time can elapse before such 

revised blocks are put into service in 

the affected exchange, in certain cases 

it may be desirable to make temporary 

changes in these exchanges, which, 

however, should be done restrictively. 

When such changes are made, a temporary 

change instruction is prepared, 

which is distributed to the exchanges 

concerned. Changes are then introduced 

in a similar way to the exchange 

data in accordance with fig. 4, i.e. the 

change is checked before putting into 

service and also a new load tape is 

generated. 

Experience has shown that only a fraction 

of all the temporary changes that 

are made in an exchange are initiated 

by error messages from the exchange 

itself. This is because the software is 

utilized on many markets in many different 

exchanges. Thus the errors are 

often detected at some other exchange 

and are corrected before they have 

had time to give rise to operational 

disturbances at the exchange in question. 

Moreover, some of the operational 

disturbances could no doubt have 

been avoided if all the temporary 

changes sent to the exchange had 

been introduced. 

Support system APS 

As has been mentioned earlier, APS is 

to be described in a later issue of 

Ericsson Review. Already now it can 

be said that it constitutes an advanced 

aid for the administration and production 

of the requisite software, and for 

producing a separate program package 

for each exchange. APS consists 

of a program system that is run on an 

IBM 370 commercial computer, and 

can at first hand be compared with a 

compiler for an administrative computer. 

However, apart from a compiler's 

translating functions from one 

code to another, APS also has functions 

for program testing, program assembly, 

program library etc. 

Summary 

With the introduction of the SPC technique 

a considerable part of the development 

and production work was 

transferred from hardware to software. 

It has therefore been necessary to 

develop design and handling methods 

and aids for the software equivalent to 

the existing methods for the hardware. 

However, many problems have proved 

to be common for the two types of products, 

and many parallels can be 

drawn between hardware and software 

production. 

A number of successively developed 

methods for handling software have 

been dealt with in this article, but the 

development is by no means at an end. 

A continuous rationalization of the 

software production is at least just as 

essential as rationalization of the hardware 

production. Moreover, since the 

software technique is a much more recent 

innovation, it can be expected 

that work in the field of rationalization 

will be lively even in the future. 

References 

1. Meurling, J., Noren, L.-O. and 

Svedberg, B.: Transit Exchange 

System AKE 132. Ericsson Rev. 50 

(1973): 2, pp. 34—57. 

2. Noren, L.-O. and Sundstrom, S.: 

Software System for AKE 13. 

Ericsson Rev. 51 (1974): 2, pp. 34 

—47. 

3. Nilsson, R. and Noren, L.-O: Inplant 

System Testing. Ericsson 

Rev. 53 (1976): 1, pp. 19—27.

WORLDWIDE 

NEWS 

Guests from all over the world 

celebrated the 

LM ERICSSON CENTENARY 

The celebration of the LM Ericsson centenary year culminated the first week in May 

when about 450 prominent guests had been invited to the parent company in Stockholm 

and a well-filled two-day program. The guests represented no less than 68 countries—there 

were Communications Ministers, General Directors, Technical Directors, 

Heads of administrations, certain suppliers, licensees, press representatives etc. etc. 

The main points of the program were as follows: 

• Symposium "Telecommunications in a changing world" 

• Presentation of LM Ericsson's technical resources 

• Preview of the National Museum exhibition "The Centenary of the Telephone" 

• King Carl XVI Gustaf presents the newly instituted LM Ericsson Prize of 100,000 

Swedish crowns to the American Harold Rosen for outstanding contributions within 

telecommunication engineering 

• The King inaugurates the Lars Magnus Ericsson Memorial Room in the new Museum 

of Telecommunications 

• Jubilee banquet in the Stockholm Town Hall 

Harold Rosen's prize address 

Dr. Harold A. Rosen's address "The 

History of Geostationary Communications 

Satellites" took place in the Museum 

of Technology in Stockholm. Dr. 

Rosen is the first winner of the newly 

instituted LM Ericsson Prize of 100.000 

Swedish crowns for "significant contributions 

within telecommunications en- 

Applause for Dr. Harold Rosen when receiving the LM Ericsson Prize from the hand of the 

King. Far left the Chairman of the Board of LM Ericsson, Dr. Marcus Wallenberg. Centre 

the President of LM Ericsson, Bjorn Lundvall 

gineering" which is to be awarded every 

third year. The Chairman of the prize 

committee. Dr. Hakan Sterky, made a 

short introductory address and presented 

Dr. Rosen, whose address is given in its 

entirety on pages 110—117 of this issue. 

After the address the prize was presented 

to Dr. Rosen by the King. 

Jubilee banquet with the King 

as the guest of honour 

It was an impressive banquet that was 

held in Stockholm Town Hall, and which 

was attended by about 730 persons, with 

the King as the guest of honour. 

The foreign guests included Communications 

Ministers and State Secretaries 

from the Sultanate of Oman, Saudi 

Arabia, Kuwait. Brazil and Venezuela. 

The Swedish government was represented 

by the Minister of Communications, 

Bengt Norling, and the Minister of Industry, 

Rune Johansson. 

International symposium 

A dominating feature of the jubilee 

program was the telecommunications 

symposium held in the large lecture hall 

of the International Fair in Stockholm 

during the mornings of two successive 

days. Speakers from all six continents 

spoke on the iheme "Telecommunications 

in a changing world". 

The addresses are given in their entirety 

in a special issue of Ericsson Review. 

Rededication of the Lars 

Magnus Ericsson Memorial 

Room in the Museum of 

Telecommunications 

The Lars Magnus Ericsson Memorial 

room from 1903, which has been moved 

from the old LM Ericsson factory at Tulegatan 

in Stockholm and has been rebuilt 

in the new Museum of Telecommunications, 

was inaugurated by King Carl XVI 

Gustaf of Sweden on one of the jubilee 

days, after the President of LM Ericsson, 

Bjorn Lundvall, had related the history of 

the Memorial Room. 

The room used from 1903 as an exhibition 

room for the company products, 

and for Board meetings and general 

meetings of the shareholders. 

161

Dr. Christian Jacobceus chaired the telecommunications 

symposium. He was also secretary 

of the prize committee that selected this 

year's winner of the telecommunication prize 

International industrial prize to 

LM Ericsson 

Each year the French organization 

Institut International de Promotion et tie 

Prestige awards an international prize to 

an industrial enterprise whose activities 

are judged by an international jury to 

deserve recognition. The Tessin Institute 

in Paris is represented on the jury, which 

includes representatives from 27 countries. 

The prize is considered by many as 

the Nobel Prize of industry. 

This year the prize was awarded to LM 

Ericsson for their contributions as regards 

the development of the world's telecommunications 

during the last 100 years. 

The prize was presented by Madame 

Gisele Rt

LM Ericsson Technics 

In connection with a presentation of 

LM Ericsson technics the new Technical 

Director, Bjorn Svedberg, delivered an 

address. During the course of the address 

a demonstration was given of the AXE 

exchange which is being installed in Sodertalje, 

a town a few miles south-west of 

Stockholm. Large TV monitors were used 

for the demonstration and the pictures 

were transmitted direct on a link from 

Sodertalje. 

Bjorn Svedberg said, among other 

things: 

— 'Through the technical developments 

that are going on around us all the time, 

we are getting more and more advanced 

telecommunication services and products. 

But what then does "more advanced" 

mean for the people affected, and how 

does this affect the products 

Subscribers who ring from Stockholm 

to Sydney observe that it sounds well 

despite the distance, but hardly give the 

technical problems a thought. If the subscribers 

only realized the enormously 

comprehensive systems and the untold 

number of components that were activated 

when a long-distance call was made, they 

would most likely never dare to make 

one. But everybody is concerned about 

how it "sounds". A good sound quality, 

such that the voice can be identified and 

the speech understood, is therefore one 

of the most important fields in technical 

development.' 

As an example the new ERICOFON 

700 was demonstrated. This telephone 

set has an electret microphone in which 

an easily-moved thin plastic diaphragm, 

which is charged electrically, is affected 

by sound waves from speech, and in 

which the micro-electronics in the speech 

circuit give a very high technical transmission 

quality of the speech. 

Increased knowledge of components 

— 'New digital transmission systems, 

which for telecommunications administrations 

mean reduced costs for copper 

lines in the local network, since parts of 

the exchange equipment (remotely controlled 

concentrators) can in future be 

moved nearer the subscriber, are now 

being designed. The whole of this technique, 

with its specialised and highly integrated 

semiconductor techniques, will 

result in greater demands on the designer's 

knowledge of the technical possibilities 

and limitations of the components. 

This means that collaboration between 

the system and component designers 

will increase. Good contacts and resources 

for the development and production 

of semiconductors is necessary for a 

telecommunications enterprise.' 

Classic mistake 

— 'We put our first computer-controlled 

(SPC) telephone exchange in operation 

in Tumba, a suburb of Stockholm, 

in 1968, and it is still giving excellent 

service. However, this local exchange 

system was too large and too complicated 

for export on a large scale. 

That now almost classic mistake that 

we and all other companies made, who at 

that time took up the development of 

SPC systems, was to underestimate the 

difficulties of producing computers and 

software for the control of telephone exchanges. 

The reliability and size requirements 

were so severe that the usual computer 

manufacturers were unable to help 

us on this occasion. 

Since then thousands of man-years 

have been devoted to the development of 

SPC systems and great progress has been 

made. In our new systems (for example 

AXE) the control and checking functions 

are divided up between a large central 

processor and a number of small regional 

computers with special programs, which 

has been possible thanks to modern circuit 

techniques. 

The reason that the exchanges have 

such a structure is that the computer capacity 

can then be obtained in the form 

of building blocks in a modular system. 

By this means the system can be adapted 

in the best way for use in different types 

or sizes of exchanges. The modular structure 

is also necessary in order to be able 

to introduce new techniques successively.' 

Svedberg also pointed out how important 

it was to design the computer-controlled 

exchange systems so that the staff 

responsible for the day-to-day operation 

and maintenance were able to understand 

the best way of handling such systems. 

Man—machine 

— 'A good man—machine relationship 

is extremely important if it is to be possible 

to get the most out of the systems. 

The computer-controlled exchanges are 

extremely complicated but they are designed 

so that outwards they are simple 

and thus easy to handle. A well designed 

high-level program language helps to 

make it possible to understand what 

happens in the system. Experience of the 

program language PLEX. developed by 

ELLEMTEL. has hitherto been good in 

the Sodertalje exchange.' 

Bjorn Svedberg, new Technical Director after 

Christian Jacobceus who retired on June 

30th 

Nordic data network 

to be equipped by 

LM Ericsson 

The telecommunications administrations 

of Denmark, Finland, Norway and 

Sweden have made out a letter of intent 

to LM Ericsson which applies for the first 

phase of an internordic public data network. 

The contract is to be signed before 

November 30th this year. 

The first phase includes equipment to 

a value of about 200 MSKr, which is to 

be put into operation at the end of 1978. 

In this stage the network will cover the 

four Nordic capitals and will serve about 

11,400 subscribers. 

The equipment comprises data exchanges, 

concentrators and multiplexors 

and will be manufactured in all the four 

countries. The network is based on the 

LM Ericsson SPC system AXE, which 

has recently been chosen by the French 

Telecommunications Administration for 

future extensions to the telephone network 

in that country. 

The background to the Nordic public 

data network is that in 1971 the Swedish 

Telecommunications Administration put 

forward an investigation report concerning 

a nationally standardized public data 

network as an alternative to the different 

types of data networks for private use. 

arranged with the aid of leased point-topoint 

telecommunication circuits, which 

hitherto have handled the rapidly expanding 

traffic. All the European countries 

had similar ideas. The four Nordic 

countries decided to build up a common 

network and last year tenders were invited. 

The project is one of the largest 

civil data ventures in the world. 

France 

chooses AXE 

On Thursday May 13th this year the 

French President in Council decided to 

order the newly developed telephone exchange 

system AXE from LM Ericsson 

for future extensions to the French telecommunications 

network. In addtion to 

AXE the Metaconta system from ITT 

and E 10 from CIT are also to be installed. 

The decisition is the result of invitations 

to tender that were set out in May 

1975 and concerned SPC telephone exchanges 

with analog switching networks. 

Other enterprises that submitted tenders, 

in addition to LM Ericsson and ITT, 

were NEC with D 10, Northern Telecom 

with SP-1, Philips with PRX 205 and 

Siemens with EWS. After very careful 

studies SP-1, PRX 205 and EWS were eliminated 

in the first stage and D 10 in the 

final stage. 

163

164 

Among the reasons that were given for 

the choice of systems was that Metaconta 

is already well known in France and that 

AXE is a very advanced telephone exchange 

system with noteworthy development 

perspectives as regards digital 

switching techniques. 

In connection with this system selection 

the French company Thomson-CSF 

will be taking over the ITT subsidiary 

companies LMT and the LM Ericsson 

subsidiary company STE. 

Through an ambitious program for the 

extension of the telecommunication network 

in France, it is planned to increase 

the number of subscriber lines from approximately 

7 million in 1975 to about 

20 million in 1982. 

Yngve Rapp 

In Memoriam 

After successful installation in Sodertdlje of the first AXE exchange, test traffic was connected 

in during April. The exchange is expected to be taken into service at the end of the year 

Yngve Rapp (born in 1903) died on 

March 12th, 1976. He joined LM Ericsson 

in 1927. From the very beginning his 

work took him abroad. During the years 

1950—1958 he was a manager in the 

Management Department for Sales. From 

1958 until he retired he was assistant to 

the Technical Director and was employed 

on operational research. 

Very early on Yngve Rapp became involved 

in network structure problems and 

became particularly interested in the 

planning of telephone networks. In this 

field he made a pioneer contribution by 

applying operational analytical methods. 

Economy and technology went hand in 

hand in his work. He evolved both basic 

theories and practical solutions. Before 

anyone else he realised the possibilities 

that computers offered for solving the 

problems. During the 1950s and 1960s he 

was one of the world's leading experts in 

this field. His results have pointed the way 

to economies in connection with network 

construction, which many administrations 

have exploited direct. Thus the telephone 

networks in several large cities in the 

world have been planned using Rapps 

methods. The International Telecommunications 

Union also apply Rapp's results 

in consultation work for the developing 

countries. Within his field Rapp has 

brought LM Ericsson to a leading position. 

The highest traffic 

capacity in the world 

The LM Ericsson system AKE 132 has 

the world's highest traffic capacity for the 

handling of national and international 

telephone traffic. This system has been 

used for the transit exchange at Hammarby. 

in Stockholm, which was recently 

taken into service by the Swedish Telecommunications 

Administration. The 

traffic capacity for a fully built out system 

amounts to 200 calls a second or 

750,000 connections an hour, which by a 

good margin surpasses all other existing 

telephone systems. 

The LM Ericsson SPC system AKE 

132 is a further development of AKE 

13. with a new multiprocessor system 

with integrated circuit techniques and 

dynamic MOS memories. The central 

processor has been relieved of the simple 

routine work by the introduction of 

regional processors. 

The first stage of the Hammarby exchange 

comprises 12,000 lines, divided up 

between two data processing blocks, each 

with a synchronously duplicated processor. 

The exchange can be built out to 

60,000 multiple positions, corresponding 

to about 300,000 equivalent lines, which 

makes possible a speech traffic of 25,000 

erlangs. 

Now that Yngve Rapp is no longer with 

us, his friends and colleagues will remember 

him as an extremely stimulating fellow 

worker. His lively intellect and wide 

general knowledge made his company 

very rewarding both at work and outside 

work. We thank him for his friendship. 

Christian Jacobieus 

History of 

LM Ericsson in a 

Jubilee Book 

"LM Ericsson 100 years" is the principal 

title of a book in three volumes with 

a total of just over 1,200 pages, which was 

prepared for the 100-year jubilee. Volumes 

I and II describe the company's 

economic and commercial history during 

the periods 1876—1932 and 1932—1976 

respectively and have been written by 

Arthur Attman, who is Professor of Economic 

History at Gothenburg University, 

and Jan Kuitse and Ulf Olsson, who are 

lecturers there. Volume III comprises the 

technical development during the 100- 

year period, and has been written by Dr. 

Christian Jacobams together with present 

and former employees of LM Ericsson. 

In the authors' foreword Professor Attman 

says that LM Ericsson's history offers 

an unusual opportunity of dealing 

with both the fundamental problems in all 

company development, namely how the 

production and market relationships have 

developed and the role that financial and 

owner questions have played. Quite early 

on LM Ericsson went outside Sweden's 

boundaries. The company had to hold its 

own in the face of international competition. 

The jubilee book is at present available in 

Swedish, and an English edition will be 

ready at the beginning of 1977. When ordered 

through the general bookshops 

the price is 400 SKr. excluding value 

added tax. Employees, pensioners and 

shareholders of Telefonaktiebolaget LM 

Ericsson can obtain the book at a substantially 

reduced price.

The Ericsson Group 

m 

With associated companies and representatives 

EUROPE 

SWEDEN 

Stockholm 

1. Telefonaktiebolaget LM Ericsson 

2. L M Ericsson Telemateriel AB 

1. AB Rita 

1. Sieverts Kabelverk AB 

1. Svenska Radio AB 

5. ELLEMTEL Utvecklings AB 

1. AB Transvertex 

4. Svenska Elgrossist AB SELGA 

1. Kabmatik AB 

4. Holm & Ericsons Elektriska AB 

4. Mellansvenska Elektriska AB 

4. SELGA Mellansverige AB 

Alingsas 

3. Kabeldon AB 

Gothenburg 

4. SELGA Vastsverige AB 

Kungsbacka 

3. Bota Kabel AB 

Malmo 

3. Bjurhagens Fabrikers AB 

4. SELGA Sydsverige AB 

Norrkoplng 

3. AB Norrkopings Kabelfabrik 

4. SELGA Dstsverige AB 

Nykoping 

1. Thorsman & Co AB 

Sundsvall 

4. SELGA Norrland AB 

EUROPE (excluding 

Sweden) 

DENMARK 

Copenhagen 

2. L M Ericsson A/S 

1. Dansk Signal Induslri A/S 

3. GNT AUTOMATIC A/S 

FINLAND 

Jorvas 

1. Oy L M Ericsson Ab 

FRANCE 

Colombes 

1. Societe Francaise des 

Telephones Ericsson 

Paris 

2. Thorsmans S A R.L 

Boulogne sur Mer 

1. RIFA S.A. 

Lannlon 

6. Societe Lannionaise 

d'Electronique SLE-CITEREL 

Marseille 

2. Etablissements Ferrer-Auran S.A. 

IRELAND 

Dublin 

1. L M Ericsson Ltd 

Drogheda 

1. Thorsman Ireland Ltd 

ITALY 

Rome 

1. FATME Soc per Az. 

5. SETEMER Soc. per Az. 

2. SIELTE Soc. per Az. 

The NETHERLANDS 

Rijen 

1. Ericsson Teleloonmaatschappij 

B.V. 

NORWAY 

Nesbru 

3. A/S Elektrisk Bureau 

4. A/S United Marine Electronics 

Oslo 

2. SRA Radio A/S 

4. A/S Telesystemer 

4. A/S Installator 

Drammen 

3. A/S Norsk Kabelfabrik 

POLAND 

Warszaw 


PORTUGAL 

Lisbon 

2. Sociedade Ericsson de Portugal 

Lda 

SPAIN 

Madrid 

1. Induslrias de Telecomunicaci6n 

S.A. (Intelsa) 

1. L M Ericsson S A 

SWITZERLAND 

Zurich 

2. Ericsson AG 

UNITED KINGDOM 

Horsham 

4. Thorn-Ericsson Telecommunications 

(Sales) Ltd. 

2. Swedish Ericsson Rentals Ltd. 

5. Swedish Ericsson Company Ltd. 


(Mfg) Ltd 

London 


Ltd. 

4. United Marine Leasing Ltd 

4. United Marine Electronics (UK) 

Ltd. 

WEST GERMANY 

Hamburg 

4. UME Marine Nachrichtentechnik 

GmbH 

Hanover 

2. Ericsson Centrum GmbH 

Ludenscheid-Piepersloh 

2. Thorsman & Co GmbH 

Representatives In: 

Austria, Belgium. Greece, Iceland. 

Luxembourg, Yugoslavia 

LATIN AMERICA 

ARGENTINA 

Buenos Aires 

1. Cla Ericsson S.A.C.I. 

1. Industrias Electricas de Quilmes 

S A. 

5. Cia Argentina de Telefonos S.A. 

5. Cla Entrerrianade Telefonos S A. 

BRAZIL 

Sao Paulo 

1. Ericsson do Brasil Comercio e 

Industria S A. 

4. Sieite S.A. Instalacoes Eletricas 

e Telefonicas 

4. TELEPLAN, Projetos e Planejamentos 

de Telecomunicacoes S.A. 

Rio de Janeiro 

3. Fios e Cabos Plasticos do 

Brasil S.A. 

Sao Jose dos Campos 

1. Telecomponentes Comercio 

e Industria S A. 

CHILE 

Santiago 

2. Cia Ericsson de Chile S A 

COLOMBIA 

Bogota 

1. Ericsson de Colombia S A 

Call 

1. Fabricas Colombianas de Materials 

Electricos Facomec S.A. 

COSTA RICA 

San Jose 


ECUADOR 

Quito 

2. Telefonos Ericsson C A 

GUATEMALA 

Guatemala City 

7. Telefonaktiebloagel LM Ericsson 

HAITI 

Port-au-Prince 

7. LM Ericsson 

MEXICO 

Mexico D.F. 

1. Teleindustria Ericsson, S A. 

1. Latinoamericana de Cables 

S.A. de C.V. 

2. Teletonos Ericsson S A 

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

PANAMA 

Panama City 

2. Telequipos S.A. 

PERU 

Lima 

2. Cla Ericsson S.A. 

EL SALVADOR 

San Salvador 


URUGUAY 

Montevideo 

2. Cia Ericsson S A. 

VENEZUELA 

Caracas 

1. Cia An6nima Ericsson 


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 

2. Societe- Marocaine des Telephones 

et Telecommunications 

"SOTELEC" 

TUNISIA 

Tunis 


ZAMBIA 

Lusaka 

2. Ericsson (Zambia Limited) 


Installation Branch 

Representatives In 

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, Moi, 

iviaua, IVICIUI eicniid, IVIUzambique, 

Namibia, Niger, Nigeria, 

>lic of South Africa, Reunion, 

Senegal, Sudan, buaan, Tanzania, lanzama, Tunisia, ii 

Uganda, ia Upper MnnPf Volta, Vnlfa Zaire. 7airo 

ASIA 

INDIA 

Calcutta 

2. Ericsson India Limiled 

INDONESIA 

Jakarta 

2. Ericsson Telephone Sales 

Corporation AB 

IRAQ 

Baghdad 

7. telefonaktiebolaget LM Ericsson 

IRAN 

Teheran 

3. Simco Ericsson Ltd 

KUWAIT 

Kuwait 


LEBANON 

Beirouth 

2. Societe Libanaise desTelephones 

Ericsson 

MALAYSIA 

Shah Alam 

1. Telecommunication Manufacturers 

(Malaysia) SDN BHD 

OMAN 

Muscat 


THAILAND 

Bangkok 

2. Ericsson Telephone Corporation 

Far East AB 

TURKEY 

Ankara 

2. Ericsson Turk Ticaret Ltd 

Sirketi 


Bahrein Bangladesh, Burma, Cyprus, 

Hong Kong, Iran, Iraq, Kuwait, 

Lebanon, Macao, Nepal, Oman, Pakistan, 

Philippines, Saudi, Arabia, 

Singapore, Sri Lanka, Syria, United 

Arab Emirates. 

UNITED STATES and 

CANADA 

UNITED STATES 

Woodbury N.Y. 

2. LM Ericsson Telecommunications 

INC 

New York, N.Y. 

5. The Ericsson Corporation 

CANADA 

Montreal 

2. L M Ericsson Ltd. 

AUSTRALIA and 

OCEANIA 

Melbourne 

1. L M Ericsson Ply. Ltd. 

1. A E.E. Capacitors Pty. Ltd. 

5. Teleric 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 

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