ericsson review - ericssonhistory.com

ERICSSON 

REVIEW 

1 1978 

OPERATIONAL EXPERIENCE FROM AXE 10 IN SODERTALJE 

A NEW INTERNATIONAL EXCHANGE IN KUWAIT 

STORED PROGRAM CONTROLLED PABX, ASB 100 

FIELD TRIAL WITH COMMON CHANNEL SIGNALLING 

60 MHZ COAXIAL CABLE SYSTEM FOR 10800 CHANNELS 

DO THE MEDIA UNDERSTAND TELECOMMUNICATIONS

ERICSSON REVIEW 

Vol.55, 1978 

Contents 

Display Systems 

Page 

Colour Display System SEMIGRAF 240 86 

Electronic Equipment for Defence Applications 

Laser Activities at LM Ericsson 66 

Satellite Communication using a Multi-Beam Array 126 

Operation and Maintenance 

Operational Experience from AXE 10 in Sodertalje 2 

Operational Experience from the Mollison International 

Switching Centre in London 58 

Operational Experience of ANA 30 in Arhus 92 

AXB 20 - Operation and Maintenance Characteristics 106 

Power Supply Systems 

A New Generation of Power Supply Equipment, Type BZD 112 46 

Private Exchanges 

Stored Program Controlled PABX, ASB 100 11 

Telephone Exchange Systems 

A New International Exchange in Kuwait 8 

Field Trial with Common Channel Signalling 20 

Saudi Arabia-the Largest Telephone Project in the World 42 

History of Local Telephone Switching in Australia 

and Background to the AXE Decision 114 

New Generation of Ringing and Tone Signalling Equipments, BKL 600 130 

Digital Group Selector in the AXE system 140 

AXE 10 with Digital Group Selector in the Telephone Network 150 

Transmission Technique 

60 MHZ Coaxial Cable System for 10800 Channels 28 

Digital Multiplex Equipment for 8 and 34 Mbit/s Line Systems 76 

New Generation of 120 and 480-Channel FDM Systems 

for Two-Wire Cable Operation 96 

Miscellaneous 

Do the Media Understand Telecommunications 38 

COPYRIGHT T E LEFON AKTI E BOL AG ET LM ERICSSON STOCKHOLM SWEDEN 1978

ERICSSON REVIEW 

NUMBER 1 • 1978 • VOLUME 55 

Copyright Telefonaktiebolaget LM Ericsson 

Printed in Sweden, Stockholm 1978 

RESPONSIBLE PUBLISHER DR. TECHN. CHRISTIAN 

JACOB/EUS 

EDITOR GUSTAF O 

DOUGLAS 

EDITORIAL STAFF FOLKE 

BERG 

EDITOR'S OFFICE S-126 25 

STOCKHOLM 

SUBSCRIPTION ONE YEAR $6.00 ONE COPY $1.70 

PUBLISHED IN SWEDISH, ENGLISH, FRENCH AND 

SPANISH 

Contents 

2 

8 

11 

20 

28 

38 

Operational Experience from AXE 10 in Sodertalje 

A New International Exchange in Kuwait 

Stored Program Controlled PABX, ASB 100 

Field Trial with Common Channel Signalling 

60 MHZ Coaxial Cable System for 10800 Channels 

Do the Media Understand Telecommunications 

COVER 

Line repeater for 60 MHZ coaxial cable system for 

10 800 channels

Operational Experience from AXE 10 

in Sodertalje 

Sten Rimbleus 

The Swedish Telecommunications Administration has operational experience of 

SPC exchanges which goes back to 1968, when the first AKE 12 exchange was 

put into operation in Tumba near Stockholm. Since then a total of three AKE 13 

exchanges have been installed in Stockholm and Gothenburg. The operational 

experience from these has been good, as has been reported in previous articles in 

Ericsson Review* ~ 3 . The present article describes the Swedish Telecommunications 

Administration's field trial and eight months' operational experience from a new 

generation of SPC exchanges, namely from the first AXE 10 exchange in Sodertalje. 

The installation has already been described in a previous issue of Ericsson 

Review 4 . 

UDC 621.395.722 

681.3.065 

The Sodertalje exchange 

Sodertalje is the zone centre for the Sodertalje 

trunk code area. A number of 

group centres and terminal exchanges 

are connected to the exchange. There 

are direct routes to Stockholm and nearby 

smaller communities and to a number 

of other cities in the country, of 

which Gothenburg and Malmo are the 

largest, fig. 1. 

On March 1st, 1977 the new 3000-line 

AXE 10 exchange in Sodertalje was taken 

into service. It then took over the 

corresponding number of lines from the 

existing AGF exchange, which served 

approximately 32 000 subscribers. This 

was the first step in a successive replacement 

of the AGF exchange (500- 

line selectors) by AXE 10. 

The new exchange was put into service 

with close cooperation between manufacturer 

and customer, which has to a 

great extent contributed to a successful 

result. 

The Telecommunications 

Administration's field trial 

Objectives 

Before the AXE 10 exchange was put 

into operation the Administration's staff 

carried out a 2-week continuous field 

trial in order to check 

Fig. 1 

Sodertalje trunk code area with some of the 

larger routes 

— Route 

^ ^ High usage route

3 

STEN RIMBLEUS 

Stockholm Telecommunication Area 

Swedish Telecommunications Administration 

Fig. 2 

The brochure distributed by the Swedish Telecommunications 

Administration when the AXE 

exchange was to be put in service 

The Swedish telephone network is to undergo a considerable 

renovation The telephone exchanges will therefore 

be replaced by new, computer-controlled exchanges 

that will permit a large number of new telecommunication 

facilities for the subscribers in the future. 

The work will start here in Sodertalje on March 1st this 

year, when approximately 3000 telephones in the number 

series 30 000 - 32 999 will be switched over to a computercontrolled 

telephone exchange AH the changeover work 

will be carried out at the telephone exchange, and it will 

not be necessary to change your telephone set 

The new telecommunication facilities will be introduced 

gradually and the immediate changes will be that 

• the dialling tone comes quicker 

D the pitch of the signal is changed 

• the ringing signal comes every 6th second instead of 

every 10th 

• the reference tone is changed to a triad 

The next stage of the modernisation program is planned 

for the second half of 1978 All telephones in Sddertalie 

with numbers that start with 1. 3, 6 or 8 will be connected 

to the new telephone exchange in 2-3 years At that time 

it will also be possible to obtain all the new telecommunication 

facilities. 

We will be contacting you again later on and we will then 

be explaining what these facilities are and how they 

function. 

THE TELECOMMUNICATIONS ADMINISTRATION 

Sodertalje 

— that the operational reliability of the 

exchange met the set requirements 

— that the traffic with interworking exchanges 

functioned satisfactorily 

— that the operating instructions provided 

took into account all the operating 

routines 

— that in other respects the exchange 

was ready to be taken into service. 

Execution 

The field trial started with the loading 

of the exchange and subscriber data required 

for operation. The exchange was 

loaded with internal traffic as well as 

traffic to and from interworking exchanges. 

It was considered as being in 

service, and thus all handling was done 

in accordance with the applicable operating 

and maintenance routines. 

The field trial comprised some 30 different 

activities, which were carried out 

mainly during the daytime. During the 

night the exchange was unmanned, 

with the remote alarm system connected 

to the Stockholm maintenance 

centre. 

Some of the most interesting trial activities 

were: 

a. Supervision of test traffic. This comprised 

the reading or checking of 

— the counter for the subscriber traffic 

generator 

— call connections 

— the results of the weekend tests 

described below 

— the results of the supervisory tests 

that were carried out 

— fault printouts (that they were obtained). 

It also included keeping a journal of 

fault printouts and any measures required 

to correct faults. 

b. Weekend tests, an unmanned longterm 

test that was started on the Friday 

evening and finished Monday 

morning. Test traffic, traffic recording 

and supervision functions were 

connected in during this test. 

c. Traffic recording for verifying the test 

traffic and traffic recording functions 

d. Alarm and alarm transmission for 

checking local alarm functions and 

the transmission of alarms to a superior 

centre. 

e. Regular charging output for checking 

that the charging was correct. 

f. Fault diagnosing, repair and repair 

checking in connection with the simulation 

of 

— permanent faults in the synchronously 

duplicated central processor 

— permanent faults in the current 

feeding 

— permanent faults in memories 

— temporary faults in various devices. 

Activity f. comprised checking that the 

automatic fault analysis functioned 

properly by giving the expected fault 

printouts, and also that the operating 

instructions were adequate. The faults 

that were detected during the various 

stages of the field trial were corrected 

as they arose. 

Result 

The faults were recorded in a journal 

and divided into categories, such as service 

quality, system restart and breakdown. 

The Telecommunications Administration 

had set requirements for each 

category in the form of the maximum 

number of permitted faults or maximum 

loss of traffic. The test showed that 

these requirements were met with a 

good margin, and as a result it was decided 

to put the AXE 10 exchange into 

service on March 1 st, 1977 at 4 a.m. 

Putting into service and 

subcriber reactions 

When the exchange was put into service, 

3000 subscriber lines from the 

AGF exchange were connected in. The 

number series in question included 

2430 ordinary subscriptions and also 

PABXsubscribersandthree-coin instruments. 

Before the exchange was put into service 

all subscribers had received a leaflet 

from the Administration's Sales Department 

with diverse information concerning 

the changeover, fig. 2. 

The changeover was planned down to 

the last detail. Naturally the morning

4 

with its heavy traffic load was awaited 

with great suspense. Incidentally, some 

fifty representatives of LM Ericsson, 

ELLEMTEL and the Swedish Telecommunications 

Administration were present 

for this historical event. 

The traffic recordings showed a successive 

increase in traffic volume and fault 

complaints started to come in. The necessary 

corrections were carried out as 

the faults appeared. The total number 

of fault complaints was about 100 during 

the first day, 20 during the second 

day and 10 during the third day. The 

types of faults that occurred and the 

reactions of the subscribers are given 

in a summary on the last page of this 

article. 

Operating statistics 

When introducing a new system it is important 

to obtain confirmation that the 

system really meets all the requirements 

laid down in the design guidelines. A 

thorough follow-up of the first exchange, 

including the rectifying of any deficiencies 

in design and handling, simplifies 

the work on subsequent exchanges 

very considerably. 

The built-in supervisory functions of 

AXE 10 have been an excellent aid in 

this respect. These functions have been 

supplemented with traffic route testers, 

for checking the operational reliability, 

and detailed operating statistics in 

which all faults and deficiencies as re- 

gards function and handling are entered. 

Operational reliability 

Test traffic was generated by the traffic 

route testers and the results show a 

successively increasing operational reliability. 

The loss of internal traffic during 

the first month was 0.9%, but after 

four months of operation the loss had 

fallen to as low as 0.03 %. 

Traffic recordings 

The system includes flexible functions 

that are of great value for traffic recording 

purposes. The traffic has therefore 

been followed up regularly by means of 

traffic recordings, the results of which 

have been analysed. For example, the 

congestion on one junction route occasionally 

amounted to 3 — 4 %. The route 

has since been enlarged and an extract 

from the traffic recording results for October 

is given in fig. 3. 

Hardware faults 

Only one design fault has been found, 

see item 1 in the summary. A number of 

printed board assemblies with faulty 

components have also been localized 

and replaced. 

Software corrections 

A number of program corrections were 

carried out during the first five months 

in service. Five cases were caused by 

incorrectly specified time limits and 

were cleared on the very first day of 

operation. Ten other faults have dis- 

SDT*AXE*1 0225 TW1 TIME 771010 1001 PAGE 1 

TRAFFIC RECORDING RESULTS 00 

TRG RBNR NRP RPL PRE 

1 2 1 12 1 

Fig. 3 

The result ot a one-hour traffic recording in 

October 1977 

TRG Traffic recording group number 

RBNR Recording batch number 

NRP Number of recording periods 

RPL Recording period length (Number of basic 

recording periods) 

RPERN Recording period number 

R Symbolic route number 

TRAFFIC Traffic flow In erlangs 

CALLS Number of calls 

CONG Call congestion as a percentage 

NDV Number of devlces/llnes/llnks connected In 

NBL01 Number of blocked devlces/llnes/links at the 

start of a recording period 

NBL02 Number of blocked devlces/llnes/links at the 

end of a recording period 

DATE Date 

TIME Time 

• High usage routes

Fig. 4 (left) 

The operation and maintenance manual, comprising 

ten binders 

Fig. 5 (right) 

Tape cassette, to which the central processor 

feeds out information regarding subscriber call 

markings. One cassette holds the information for 

all subscribers in the exchange 

Fig. 6 

Control room. 

The staff in the control room have access to, for 

example, typewriters, displays, alarm panels and 

tape cassettes, and with the aid of these they can 

receive and feed in information to the AXE 

exchange. Some examples of received information 

are alarms, fault indications and traffic recording 

information. The information fed in to the 

exchange can concern, for example, traffic 

routing, special subscriber facilities such as 

abbreviated dialling, the tracing of calls and 

charging checks. 

Fig. 7 (left) 

Switch room. 

The printed board assemblies for the exchange 

equipment are mounted in magazines which are 

placed in shelves. The shelves are covered with 

protective plates. The shelves and plates are 

finished in a grey colour, which together with 

warm colours on walls and ceiling give the switch 

room a quiet and comfortable appearance 

Fig. 8 (right) 

Typewriter terminal. 

The man-machine communication takes place via 

such aids as typewriters. The typewriter is a quiet 

matrix printer. 

Fig. 9 

Floor plan for the AXE 10 equipment for a total of 

12000 lines. The rows marked in red serve the 

3000 lines already in operation. The rows take up 

only 1/3 of the space of the corresponding 

500-line selector racks 

TSS Signalling subsystem (or outgoing and Incoming 

lines 

GSS Group selector subsystem 

SSS Subscriber subsystem 

CPS Central processor subsystem 

IOS Input/output subsystem

Fig. 10a 

Minor automatic system restarts. Often caused 

by software faults. Takes 3 seconds. Established 

calls are not affected 

Fig. 10b 

Major automatic system restarts 

• Often caused by software faults. Takes 3 seconds. 

Established calls are disconnected 

Includes reloading. Caused by software faults alone or 

In combination with hardware faults. Takes 7 minutes 

All traffic handling stops 

March May July Sept Time 

April June Aug Oct 

Fig. 10c 

Manually initiated system restarts 

• Minor restarts caused by software faults that have led 

to the holding of a switch, other devices or individual 

subscribers 

Ma|or restarts caused by software faults that have led 

to major traffic disturbances 

turbed the traffic in one way or another, 

whereas the remaining 35 faults during 

the five-month period consisted mainly 

of small adjustments intended to improve 

the handling characteristics. 

Thanks to the modular structure and design 

of the software it has been easy to 

make corrections. These have always 

been carried out by the designer concerned 

and verified in the system test 

equipment before being introduced in 

Sodertalje. 

System restart 

The system automatically carries out a 

system restart when implausible data 

are detected or there is an error in the 

program handling sequence. Restart 

can also be ordered manually by the 

operator. This function is an excellent 

means of maintaining the operational 

readability of the system since it limits 

the effects of a serious fault. In addition 

an informative printout is obtained in 

connection with the restart, which gives 

the designer the necessary basic data 

for carrying out corrections. 

Figs. 10 a—c show the frequency of the 

various types of restarts since the exchange 

was put into operation. Most of 

the necessary software corrections had 

been carried out by August 1977, so that 

for example the number of manual restarts 

had decreased considerably by 

then. It should also be pointed out that 

major system restarts were partly caused 

by incorrect handling. 

System stop 

The only system stop that has occurred 

so far took place after 10 days in service 

and lasted approximately 15 minutes. It 

was caused by a combination of software 

and hardware faults, a type of fault 

which, as is well known, is most difficult 

to foresee. 

Operation and maintenance 

routines 

Manning 

The AXE exchange was manned day and 

night during the first week in service and 

thereafter only during normal working 

hours (Monday-Friday 7.30 a.m. to 4 

p.m.). 

The Telecommunications Administration, 

who have responsibility for the 

operation, now have two operators stationed 

in the exchange. Their main task 

is to carry out the normal operation and 

maintenance activities. 

Administrative staff have also been stationed 

temporarily in the exchange in 

order to follow events there and to further 

develop the operation and maintenance 

routines. Installation staff from 

LM Ericsson and some designers from 

ELLEMTEL acted as advisors during the 

first two months. 

As this was the first AXE 10 exchange 

the Telecommunications Administration 

wanted to guard against unforeseen 

events. For this purpose an expert group 

was appointed, where each member was 

a specialist in his own field. The members 

worked as usual, but could be contacted 

at any time of the day or night. 

By the end of October the Stockholm 

maintenance centre had received a total 

of eight alarms during night-time which 

were serious enough to necessitate 

sending out an operator to the exchange. 

It was possible to clear all these 

faults with the aid of the existing operating 

instructions without having to call 

in the expert group. 

Documentation 

The most important documents are included 

in the operation and maintenance 

manual, which comprises operating 

instructions stating what is to be 

done, step by step, in different situations. 

The instructions are arranged per 

activity and also contain descriptions 

of commands and printouts. The operation 

and maintenance manual consists 

of ten binders, which cover the information 

needs for all activities. It was found 

that with the aid of this manual the Administration's 

operators were able to 

carry out, on their own, fairly complicated 

repairs, such as changing printed 

board assemblies in the data processing 

system, without causing operational 

disturbances. 

It is expected that only this manual will 

be needed in future AXE exchanges. As 

Sodertalje was the very first AXE 10 exchange 

it was also provided with system 

descriptions and program and hardware 

documentation.

Types of faults, measures and 

subscriber reactions 

Of the fault types and subscriber reactions given 

below, only type 1 represents a real fault. The 

other types are to be considered as mishaps 

and are difficult to foresee. Moreover, experience 

has shown that they usually do not appear 

until an SPC exchange operates in its proper 

environment. 

1. Traffic to certains PABXs did not function 

satisfactorily because of faulty system adaption, 

which in its turn was caused by ambiguities 

in the specifications. The fault was 

cleared immediately by means of a hardware 

correction. 

2. Unforeseen variations in different AGF equipments 

caused such faults as failure to establish 

speech connection, prematurely disconnected 

calls and holding. The faults were 

cleared by changing the time-dependent signals 

to and from AXE 10. 

3. Certain number series to other trunk code 

areas were erroneously barred and were 

opened by means of a correction of the exchange 

data. 

4. Missing data for a number of subscribers 

were included. 

5. A number of faulty subscriber connections 

in the main distribution frame were corrected. 

6. The built-in line test function was set to the 

prescribed limits, but these proved to be too 

narrow in view of the condition of the network. 

Many subscribers were temporarily 

blocked and the values for the line test function 

were adjusted to suit the actual network 

conditions. 

7. Because of the very short setting-up time in 

AXE 10 unwarranted fault complaints concerning 

"permanent dialling tone" were received, 

since this tone is sent out immediately 

the subscriber lifts the receiver or dials 

a trunk code. 

8. An individual supervisory function indicated 

that for 24 hours no call had been initiated 

from a three-coin instrument situated 

in a lonely place. Since the telephone turned 

out to be in working order it is likely that it 

had not been used during that period. The 

supervisory interval was therefore extended 

to 48 hours, and since then there has been 

no more indications. 

Plans for the future 

The experience gained from the Sodertalje 

exchange has helped to make possible 

the realization of previously prepared 

plans for the future earlier than 

expected. 

Extension rate 

The Telecommunications Administration's 

network now contains about 5 

million installed local lines, of which 

just over half are served by modern 

crossbar exchanges. The remainder are 

connected to AGF exchanges, the oldest 

of which have been in service for 

over 50 years. Problems concerning the 

realization of new functions, wear, 

spares and maintenance have led to the 

Administration preparing a modernisation 

plan. It comprises a long-term program 

for the replacement of AGF by 

AXE 10, with the aim that all AGF exchanges 

shall be replaced before the 

year 2000. 

Centrally stationed staff 

It is already clear that a changeover to 

AXE 10 will mean a radical improvement 

in the operation and maintenance activities. 

Thus the system permits authorized 

departments within the Administration 

to send commands via terminals 

(I/O devices) direct to the exchanges 

concerned, in order to carry out any desired 

changes. For example, the sales 

department will be able to connect in or 

disconnect subscribers direct by means 

of a command, instead of having to 

make out a work order and sending it 

to the exchange for manual action. This 

applies for most other operational activities 

that can be remotely controlled, 

for example 

— connecting in and disconnecting different 

subscriber facilities 

— traffic recording 

- traffic observation 

- reading of call meters 

— changing the charging and traffic 

routing 

- collecting statistics 

It is the aim of the Telecommunications 

Administration to successively transfer 

all operational and maintenance work 

within a geographical area to staff stationed 

at a centrally placed maintenance 

centre. From there the maintenance 

staff will be sent out to the exchanges 

when the need for manual intervention 

arises. 

Conclusion 

The operational experience obtained 

from the Sodertalje exchange has 

proved that the modular structure of 

both the system software and hardware 

makes the system easy to handle. 

Furthermore owing to the fact that the 

operational reliability already from the 

beginning has proved to be good it has 

been possible to introduce push-button 

dialling and abbreviated dialling six 

months earlier than was originally planned. 

If regard is also paid to the wide range 

of possibilities and facilities offered by 

AXE 10 —not least concerning rationalization 

and reducing the cost of the operation 

and maintenance activities —it is 

clear that this new generation of SPC 

exchanges meets the requirements of 

today and tomorrow and has thus come 

to stay. 

7 

References 

LSundblad, A.: Operating Experience 

from AKE 120, Tumba. Ericsson 

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

2. Ericsson, L. G. and Persson, A.: 

Operation and Maintenance Characteristics 

of AKE 13. Ericsson 

Rev. 54 (1977):3, pp.125-135. 

3. Ericsson, L. G. and Persson, A.: 

Operational Experience of AKE 13. 

Ericsson Rev. 54 (1977):4, pp.168 

-173. 

4. Meurling, J.: Sodertalje-the First 

AXE Exchange. Ericsson Rev. 54 

(1977):1,pp. 2-6.

A New International Exchange 

in Kuwait 

Abdullah Al-Sabej 

On August 75,7977, the subscribers in Kuwait were given the possibility of dialling 

automatic international calls. On this date, a new international SPC exchange was 

put into operation. This exchange was the first of the LM Ericsson system ARE 13 

with the processor system ANA 30. 

The ARE 13 system has previously been described in a serie of articles in Ericsson 

Review^3. 

This article will therefore only briefly describe the functions that are 

characteristic of the exchange in Kuwait as well as the experiences gained from the 

installation and putting into service of the exchange. 

UDC 621.395.722: 

681.3.065 

Fig. 1 

Street scene from Kuwait. The tall building in the 

background is the telephone exchange 

A smaller international exchange of 

non-LM Ericsson design for operator 

assisted traffic was already in operation 

in Kuwait, but due to the demand for a 

larger system to handle international 

subscriber dialled traffic, the Ministry of 

Communications announced a public 

tender in 1975. After studies of various 

bids, the Ministry selected the ARE 13 

system from LM Ericsson. Among the 

features of the ARE 13 system that received 

most consideration, were: 

— The large line capacity and traffic 

handling capability of the system, up 

to 24 000 multiple positions (triple 

exchange) and 300 000 calls per hour. 

The modularity of the system makes it 

possible to extend it economically in 

order to meet the dramatically increasing 

international traffic demand 

in Kuwait. 

— The advanced operator and charging 

facilities with toll-ticketing, TT. 

— The modular and standardized design 

of both software and hardware, 

which provides high reliability and 

easy handling. 

Installation in two phases 

In accordance with the contract the first 

phase of the ARE 13 exchange with about 

650 international circuits should be 

taken into service on 30.11.1977. However, 

through the combined efforts of all 

parties concerned, it was possible to 

take the ARE 13 into service on

9 

ABDULLAH AL-SABEJ 

Chief Engineer 

Ministry of Communications, Kuwait 

Fig. 2 

Some of the most important functions of the 

international exchange in Kuwait 

15.8.1977. Previously an ARM exchange 

with operator handled traffic containing 

150 international circuits was, however, 

installed in order to meet the increasing 

demand in a temporary way. This ARM 

exchange was taken into service on 

1.10.1976. 

The second phase of the contract involves 

extension of the ARE 13 exchange 

and conversion of the interim 

ARM exchange to ARE 13. Thus ARE 13 

will be extended to 1400 international 

circuits and 120 operator positions. The 

installation of this second phase will 

take place during 1978. 

A modern international maintenance 

centre was also included in the contract 

and was taken into service in connection 

with the first phase of ARE 13. 

The telephone network 

of Kuwait 

Kuwait has a very modern and well developed 

telephone network. The local 

exchanges are mainly ARF 102, none of 

which are older than 10 years. SPC 

technology is also now being introduced 

in the local network in the form of 

ARE 11 and AXE 10. There are also a few 

exchanges of non-LM Ericsson systems, 

with which ARE 13 is interworking. 

Due to the geography of the country, no 

4-wire transit exchanges are necessary 

on the national level. Accordingly, only 

2-wire tandem stages are used for the 

national traffic. 

The local exchanges are thus connected 

to the ARE 13 either direct or via the 

tandem stages. 

As is shown in fig. 2 the international 

ARE 13 exchange connects Kuwait to 

the rest of the world via the following 

media: 

- Satellite connections both via the 

Atlantic and the Indian Ocean satellites 

with signalling system CCITT No. 

5 

- Coaxial cable and radio link connections 

to neighbouring countries, with 

signalling system CCITT R2. 

- A small number of manual connections 

with signalling system CCITT 

No. 1. 

Some important features 

of ARE 13 

ARE 13 is built up of a switching part, 

with the well proven LM Ericsson cross-

10 

bar switch, and a control part with the 

reliable and easy-to-handle processor 

system ANA 30. 

The ARE 13 in Kuwait comprises 

approximately 300 electronic shelves 

and 11000 printed circuit boards. 

The new operator and TT system includes 

a number of features of importance 

to the Ministry. These systems 

have previously been described in 

Ericsson Review 3 . 

The operator system considerably improves 

the service for semi-automatic 

calls by the provision of on-demand 

service and automatic TT-charging. Automatic 

print-out of information concerning 

delay calls, immediate price 

advice and international conference 

calls are examples of other services that 

the ARE 13 in Kuwait provides. 

The TT-charging system utilizes the 

same hardware in the processors as 

ANA30. In this system, the price information 

is automatically calculated for 

all calls —automatic, as well as operator 

assisted —and the result is stored on 

magnetic tapes. Consequently, this TTsystem 

considerably reduces the Ministry's 

billing work. 

Installing and Testing 

The installation has been carried out by 

the Ministry with minimal supervision 

from LM Ericsson. This has been possible 

due to the familiarity of the Ministry's 

staff with the technique of the switching 

part (similar to ARF 102) and the efficient 

training programmes conducted. 

The procedure adopted for this first ARE 

exchange in Kuwait has resulted in reduced 

installation costs and thorough 

practical experience for the Ministry's 

staff. 

The staff are therefore well prepared for 

the operation and maintenance of this 

exchange, and furthermore, also for 

forthcoming installation, testing and 

operation of the contracted ARE 11 exchanges. 

Operational Experience 

Despite the fact that the installation and 

testing time of the exchange were considerably 

shortened, this world premier 

ARE 13 exchange was put into service 

with favourable result. 

Fig. 3 

International maintenance centre 

References 

1. Andersson, B. et al.: ARE Systems 

in Modern Networks. Ericsson Rev. 

54 (1977):2, pp. 54-66. 

2. Hemre, A. and Hagard, G.: The 

Software and Its Handling in ARE 

Systems. Ericsson Rev. 54 (1377):2, 

pp. 77-85. 

3. Ellstam, S. and Olsson, B.: Stored 

Program Controlled Transit Exchange 

ARE 13 with Control 

System ANA 302. Ericsson Rev. 52 

(1975):3/4, pp. 116-127. 

4. Jansson, H. and Thune, U.: TT and 

Operator Systems for ARE 13. 

Ericsson Rev. 53 (1976):4, pp. 

184-193.

Stored Program Controlled 

PABX, ASB 100 

Per Furu 

In connection with the modernisation of their PBX range LM Ericsson, in cooperation 

with ELLEMTEL and the Swedish Telecommunications Administration, 

have developed an electronic, stored program controlled PABX for up to 100 extensions. 

The objectives of the development work were to develop an easy-to-handle 

system with the greatest number of functions that the economic aspects allowed. 

Special importance was attached to achieving a system that works with good 

economy during the whole of its life as regards operation, maintenance and 

administration. 

The operator's set has been given a new design in order to simplify the handling of 

calls. In addition to normal tasks the operator also has the possibility of carrying out 

a part of the administration and supervision of the PABX. 

UDC 621.395 24 

ASB 100 is a stored program controlled 

PABX system with the programs stored 

in a permanent semiconductor memory 

(PROM) and data stored in an electrically 

changeable semiconductor memory 

(RAM). The PABX is equipped with a 

single stage, non-blocking switching 

network with full accessibility between 

extensions and the devices that carry 

traffic. 

ASB 100 is available in two different 

cabinet heights depending on the final 

capacity required. The smaller cabinet 

can be built out to 40 extensions and the 

larger cabinet has a final capacity of 100 

extensions. The system has a high traffic 

handling capacity in both cases. 

The PABX is built up entirely of printed 

board assemblies, which are mounted in 

shelves in the cabinets. The wiring is 

carried out in a rear plane that is common 

for three shelves. The smaller 

system contains one such unit and the 

larger contains two. These units, and all 

external units, such as extensions and 

external lines, are interconnected by 

means of standardized cables equipped 

with plugs. 

The system can be delivered to the 

customers as a complete, tested unit, 

which reduces the installation time considerably. 

Stored program control has made it 

possible to introduce a large number of 

new functions, which have previously 

been available only in large systems. 

The aim has been to provide these functions 

solely by additions to the software, 

as far as this is possible, and to avoid 

special equipments, wiring changes and 

special apparatus. However, space has 

been prepared in the rack for those 

functions that require extra equipment, 

and consequently a function can be introduced 

quite easily at any convenient 

time. 

The PABX permits any combination of 

Fig. 1 

ASB 100. Operator's set and cabinet for 100 extensions

PER FURU 

Subscriber Equipment Division 

Telefonaktiebolaget LM Ericsson 

Fig. 2 

Block diagram for the stored program controlled 

PABX, ASB100 

rotary dial and push-button telephone 

instruments. 

The use of push-button telephone sets, 

which in addition to the ten digit buttons 

have buttons with the star and square 

symbols, makes it possible to provide 

such facilities as 

- individual abbreviated dialling 

- automatic call diversion 

- bypassing of automatic call diversion 

- direct switching to a loudspeaking 

telephone. 

The push-button telephone sets also 

have another button, the register button, 

for calling in a register, for example 

when making an inquiry call. 

Special importance has been attached 

to the utilization of the possibilities offered 

by a stored program controlled 

system as regards operation and maintenance 

and also administration. As regards 

operation and maintenance the 

aim has been to reduce the need for 

qualified staff and training to a minimum. 

This has been achieved through 

a well designed functional system structure 

in combination with advanced test 

programs and easily understood documentation. 

The administration of the 

system has been made more efficient 

and flexible since certain tasks can now 

be allocated to the operator, and because 

it is possible to arrange central 

administration of several PABXs via the 

public telephone network. 

System design 

ASB 100 can be divided into a switching 

equipment and a control system. The 

exchange of information between these 

two takes place via a bus system. Fig. 2 

shows a block diagram of the system. 

The units shown in unbroken lines constitute 

the standard equipment in the 

exchange and the units shown in broken 

lines are supplementary equipments, 

which can be supplied if required. 

Switching equipment 

ASB 100 is equipped with an electronic 

switching network that is built up of 

thyristor crosspoints. This means that 

redirection in the switching network can 

be carried out very quickly and that the 

network can be used not only for speech 

communication but also for the connection 

of different signalling units. Such 

units include the tone sender, which 

gives different types of tone information 

to the extension, or the dialling tone receiver, 

for receiving the dialling tone 

from the public network when this occurs. 

The use of a single-stage thyristor 

crosspoint switching network makes it 

possible to order the setting up of different 

connections direct from the units 

concerned, for example extension line 

circuit and tone sender, when initiating 

a call. Thus special circuits for setting 

up the switching network are not required.

13 

When the receiver is lifted the extension 

is connected to a tone sender that sends 

the dialling tone, after which dialling 

can start. If a conventional telephone set 

with a dial is used, the dialled digits are 

received direct in the extension line 

circuit, but if a telephone set equipped 

for tone frequency key sending is used, 

the digits are received by a push-button 

dialling tone receiver, which is connected 

to the tone sender. In both cases 

the digit information is transferred via 

the bus system to the control system for 

further analysis. If the digit analysis indicates 

that the call is internal, a connection 

is set up via a free local junctor 

trunk to the desired extension. If the call 

is external, a free line is connected up 

to a dialling tone receiver. Thus the extension 

is now connected to a tone 

sender and a trunk line to a dialling 

tone receiver. 

The external number can now be dialled 

and registered in the same way as in the 

case of an internal call. 

When the public exchange works with 

decadic impulsing the external number 

is transmitted with the aid of circuits in 

the trunk line circuit regardless of 

whether the extension has a telephone 

set with a dial or a push-button telephone 

set. The dialling tone receiver is 

disconnected when the dialling tone has 

been received. In cases where there is a 

second dialling tone the receiver remains 

connected until this tone has 

been received. The extension is connected 

to the external line when the dialling 

tone ceases. The tone sender is disconnected 

when the transmission of digits 

is completed. 

When an external call comes in, the 

trunk line is connected to the operator's 

console, after which the operator can 

dial the desired extension number and 

set up the call. A characteristic feature 

of ASB 100 is that the operator works 

with only one operator link. It is used 

only when the operator is actively engaged 

in any part of the call handling. 

Other functions, which concern the 

operator's work indirectly, such as ringing, 

camp on busy, parking etc., affect 

only the units concerned, for example 

external and extension lines, and are 

controlled completely from the central 

control system. 

Control system 

The control system in ASB 100 is built up 

around processor APN 163, developed 

by LM Ericsson, which is a powerful, 

general purpose 16-bit processor that is 

designed for a number of applications in 

different fields of activity. 

The choice of memories was based on a 

desire to obtain high flexibility at a low 

cost. For this reason permanent mem- 

Fig. 3 

Operator's set

Fig. 4 

The structure of the program system 

The cabinet on the left is 

for up to 100 extensions 

The cabinet on the right is 

for up to 40 extensions 

Fig. 5 

Cabinets for the exchange 

equipment 

ories (PROM) were chosen for storing 

the programs — program stores - whereas 

the parameters that can vary from 

one installation to another are stored in 

electrically changeable memories 

(RAM)-data stores. The latter also provide 

the storage capacity required for 

storing temporary data in connection 

with the traffic in progress in the PABX. 

The data store boards are equipped with 

chargeable miniature batteries that can 

keep the voltage intact for at least 100 

hours, so that the semi-permanent data 

stored in the data store will not be lost 

in case of a power failure. 

When designing the program system in 

ABS 100 the demands that can be made 

on a modern PABX have been met as far 

as possible. In addition to the abovementioned 

division into program and 

data stores it has been the aim to facilitate 

the introduction of new functions 

and make market adaptions. The 

structure of the program system is 

shown in fig. 4. 

The program system can be divided into 

three parts: traffic programs that handle 

the actual telephony functions, monitor 

programs that supervise the program 

handling and common functions in the 

exchange, and finally operation and 

maintenance programs. 

The traffic programs in their turn can be 

divided into two parts: one procedure 

block and one line signal block. The 

program modules of the procedure 

block each cover different traffic cases 

in the exchange, whereas the line signal 

block modules constitute the interface 

between the procedure programs and 

the different hardware units in the exchange. 

In this way small program modules with 

well defined interfaces have been 

obtained. The procedure program modules 

are affected when new facilities are 

introduced and existing ones are modified, 

and the line signal program modules 

are affected, for example, when the 

PABX is adapted to new types of signalling. 

Cabinets 

ASB 100 can be supplied with two different 

cabinet heights depending on the 

final capacity required, fig. 5. The smaller 

cabinet, which accommodates one 

magazine containing three shelves, 

permits extension up to 40 extensions, 5 

local junctors, 12 trunk lines and 3 tone 

senders. The larger cabinet, which accommodates 

two magazines with three 

shelves each, permits extension up to 

100 extensions, 10 local junctors, 24 

trunk lines and 6 tone senders. At the 

manufacturing stage space is prepared 

in the cabinets not only for the control 

unit and the required traffic-carrying 

devices and switches but also for the 

extra printed board assemblies that are 

required for additional facilities. 

There is also space in the cabinets for a 

built-in power unit. 

Switching network 

The switching network in ASB 100 is 

built up of thyristor crosspoint matrices 

for symmetrical two-wire through-connection. 

The matrix capacity gives 

optimum utilization with 40 and 100 

lines. A matrix, which is accommodated 

on one printed board assembly, can 

connect 12 inputs to 28 outputs. Thus

15 

five such matrices permit connection of 

a total of 60 inputs. Of the 60 inputs, 40 

are used for connecting extensions 

while the others are reserved for connecting 

other units, for example 

operator and junction lines. The larger 

variant of ASB 100 has space for 20 

matrices, which provides the possibility 

of connecting 120 inputs to a maximum 

of 56 outputs. 

Traffic capacity 

Since ASB 100 is equipped with a nonblocking 

switching network its traffic 

capacity is determined entirely by the 

number of traffic-carrying devices. The 

system is dimensioned for a traffic volume 

of 0.17 erlangs per extension with a 

congestion of 0.01 and 20 — 40% internal 

traffic. This applies with the maximum 

number of extensions, 40 and 100 

respectively, connected. If a higher traffic 

capacity is required, this can easily 

be obtained by reducing the number of 

extensions. For example, a small system 

with 30 extensions connected can handle 

an average traffic of 0.23 erlangs per 

extension. 

Traffic facilities 

In stored program controlled systems it 

has not only been possible to introduce 

a large number of new facilities even in 

small exchanges, but also to administer 

the utilization of these facilities so that 

they can be used to the optimum extent. 

The various facilities have as far as possible 

been realized solely in software, in 

order to obtain greater flexibility and 

simpler administration. In this way it has 

been possible to eliminate rewiring and 

special apparatus. 

Basic facilities 

The basic equipment for the PABX includes 

three program store boards with 

a storage capacity of 8k words each. 

They contain the programs for all telephony 

functions offered by the exchange. 

The following functions are provided: 

— extension class of service allocation 

— internal calls 

— outgoing calls, direct or via the 

operator 

— incoming calls via the operator 

— inquiry during internal as well as external 

calls 

— automatic transfer of internal as well 

as external calls 

— add on conference 

— call diversion to a common attendance 

point. This function can be 

ordered and cancelled from pushbutton 

telephones 

— priority 

— common or automatic night service 

connections 

— universal call back 

— flexible numbering 

— choice of individual trunk line (from 

the operator) 

— group hunting 

— direct call diversion to an individual 

attendance point. The function is 

programmed by the operator and is 

ordered or cancelled by extensions 

equipped with push-button sets 

— diversion to an individual attendance 

point if no answer is obtained 

— long distance traffic control 

— call pick-up 

— individual night service connection 

— transit traffic 

— common external abbreviated dialling 

Fig. 6 

The operator's console has symbols Instead of 

explanatory text.

Fig. 7 

The lower cabinet holds three shelf magazines 

with printed board assemblies 

— individual external abbreviated dialling. 

The function is programmed by 

the operator and can be used by extensions 

with push-button sets 

— call waiting function for incoming external 

calls 

— direct switching to a loudspeaking 

telephone. 

Classification of the extensions 

Each extension can be allocated individually 

to one of 12 facility categories 

and also one or more of four categories 

for the control of long-distance calls. 

There is also the possibility of allocating 

the extensions other facility categories 

which automatically come into operation 

when the PABX is set up for night 

service. Each facility category comprises 

one or more of the following basic 

facilities: 

— open for all automatic outgoing trunk 

line traffic 

— open for operator-assisted outgoing 

and incoming trunk line traffic 

— open for transferred trunk line traffic 

— barred for cutting in 

— open for the call-waiting function initiated 

by the operator 

— vacant 

The relationship between extensions 

and facility categories is flexible and 

programmed into the data store from 

the operator's set or a typewriter terminal. 

Of the four categories used for the 

control of long-distance calls, one indicates 

that calls are permitted within the 

local area and the other three are used 

for opening up certain trunk code 

areas/subscriber numbers. In this way 

up to 32 directions, which can be defined 

with a maximum of 8 digits, can be 

opened. As can be seen from the above, 

these 32 directions can be divided into a 

maximum of three groups. 

Call pick-up 

This function means that a call to a 

free extension can be answered from 

another extension. This is arranged by 

dialling a special code, which includes 

the number of the called free extension. 

External abbreviated dialling 

ASB 100 offers the possibility of both individual 

and common external abbreviated 

dialling. This makes it possible for 

the extensions to reach certain previously 

selected subscribers in the national 

or international network by dialling 

two or three-digit numbers. This 

facility can also be used by extensions 

that are barred for national and international 

calls. The programming of the 

subscriber numbers that are to be 

reached when an abbreviated number is 

dialled is carried out from the operator's 

set or a typewriter terminal. 

The abbreviated numbers can consist of 

subscriber numbers or a part of these. In 

the latter case the additional digits required 

to complete the whole subscriber 

number can be dialled from the extension. 

This is an advantage if, for example, 

it is desired to open a whole or a part 

of a trunk code area to all extensions, or 

in the case of traffic to PABXs that are 

equipped for direct inward dialling. 

ASB 100 permits the storage of up to 35 

common abbreviated numbers in the 

smaller version and up to 90 in the 

larger. These numbers can consist of a 

maximum of 20 digits, where access 

codes and intermediate tones are also 

counted as digits. Six individual abbreviated 

numbers can be allocated to each 

of a maximum of 10 extensions in the 

smaller version and 20 in the larger. The 

individual numbers can consist of a 

maximum of 12 digits each, where the 

digits are counted in the same way as for 

the common abbreviated numbers 

above. 

Call waiting function 

Thisfunction means that when handling 

an incoming call to an extension that is 

already busy, the operator can send a 

short tone to indicate that there is a call 

waiting. The extension can then take the 

new call either by finishing off or parking 

the existing call. 

Optional facilities 

The following functions are considered 

as optional facilities because they require 

extra equipment. However, the required 

programs are included in the 

program store boards in the basic 

equipment for the exchange. 

— operator-controlled call metering 

— through-connection of trunk lines 

— individual call metering 

— paging by means of visual or radio 

signals 

— junction lines 

— busy indication panel.

17 

Fig. 8 

Printed board assembly for a 12x28 switching 

network matrix 

Operator's set and operator 

functions 

The operator is responsible for a large 

part of the service offered to the callers. 

During the design work every effort has 

therefore been made to provide a functionally 

correct design for the operator's 

console. The aim has been to achieve 

the best possible relation between man 

and machine, fig. 3. 

This has led to a minimisation of the 

number of function buttons and the use 

of explanatory symbols instead of text. 

The training of new operators is simplified 

because the set is equipped with an 

information panel, in which it is possible 

to trace the setting up of a call through 

the exchange. 

In addition to the facilities ASB 100 offers 

for the normal handling of calls, 

functions can also be included that enable 

the operator to take an active part in 

the administration of the exchange if 

desired. These comprise such functions 

as changing and checking the extension 

categories and directory numbers, 

programming of external abbreviated 

numbers and call forwarding etc. 

ASB 100 is designed for use with one 

operator's console. This is usually connected 

by means of a plug to a wallmounted 

jack, but can also, for example 

during the testing stage, be connected 

to the exchange cabinet. The console 

can be placed up to 50 m (15 ohms) 

from the exchange equipment without 

any extra equipment being required. 

Mechanical construction 

Printed board assemblies, shelves 

and cabinets 

All components in ASB 100 are mounted 

on printed boards. These have single or 

double-sided foil with the exception of 

the processor boards, which are manufactured 

using four-layer technique. 

The printed board assemblies are 

mounted in 19" shelves. Three such 

shelves form a triple magazine and constitute 

one unit with a common rear 

plane, where all wiring between the assemblies 

is carried out. The magazines 

are mounted in cabinets of two different 

sizes. 

The racks contain no wiring. All wiring 

within the magazines is done on the 

common rear planes of the magazines, 

and the wiring between magazines and 

to external units is done with the aid of 

plug-in, standardized factory-made cables. 

Power supply 

ASB 100 is normally equipped with a 

built-in power unit, which is designed 

for feeding from the mains and for providing 

the power needed to operate the 

exchange. This unit, which is placed at 

the bottom of the exchange cabinet, 

converts the a.c. mains voltage to a 48 V 

d.c. voltage. 

Installation and testing 

Because of its compact structure ASB 

100 requires comparatively little space. 

The floor area required is approximately 

2 m 2 , which also includes the necessary 

free space around the exchange. 

The installation of the exchange itself 

can be said to comprise mainly three 

activities: 

— mounting theexchangeand connecting 

external units and power 

— input of the system data 

— installation testing. 

During the design of the system and the 

establishment of the system handling 

routines the objective has been to reduce 

the installation work, and thus also 

the installation time, to a minimum. This 

has resulted in, for example, the following 

features: 

— the exchange can be delivered to the 

customer complete and tested 

— all external connections are carried 

out with standardized cables equipped 

with plugs 

— system data can be programmed 

quickly by means of special commands, 

which makes it possible to 

program in "standard data" for all extensions 

by means of a single command. 

Hence the installer does not 

need to program data individually for 

each extension, only modify data for 

the extensions where this is necessary 

— system data can be programmed up 

to four days before the PABX is put 

into operation 

— advanced test and fault localization 

programs are available if required.

18 

Fig. 9 

Typewriter terminal for communication with the 

exchange 

Operation and maintenance 

The principle for the operation and 

maintenance of ASB 100 can be summarized 

as follows: 

— the operation of the exchange is continuously 

supervised by a built-in 

supervisory system 

— if disturbances occur, measures to 

limit the effect of these are carried out 

automatically 

— all preventive maintenance and all 

routine testing during the operation 

of the exchange is avoided 

— it is possible to carry out fault localization 

down to the printed board assembly 

level with the aid of simple 

tools. 

Operational supervision 

In the case of an exchange of this size 

the program volume must be kept as 

small as possible for reasons of 

economy and reliability. 

Since the number of components is 

small and the reliability is high, ASB 100 

requires only a few supervisory functions, 

primarily for the supervision of the 

control system. 

The system contains the following 

supervisory functions that can give 

alarms: 

— a hardware circuit that supervises the 

progress of the program handling 

— a disturbance ratio supervision function 

that counts the number of connections 

and disturbances 

— supervision of the power supply unit 

when the exchange is fed from both 

the mains and batteries. 

Alarms from the supervisory functions 

of the exchange are obtained both in the 

exchange and on a lamp in the 

operator's console as follows: 

— time supervision alarm gives steady 

light 

— disturbance ratio alarm gives slowly 

flashing light 

— voltage alarm gives rapidly flashing 

light. 

It is also possible to have these alarms 

indicated on a separate panel. The exchange 

itself also contains an observation 

alarm function that indicates if any 

units are blocked or any printed board 

assemblies have been removed. 

The function "disturbance marking of 

devices and data areas" has been introduced 

in order to limit the number of 

traffic disturbances caused by technical 

faults as far as possible. 

This means that after devices or data 

areas have caused a disturbance marking 

they will not be selected until all devices 

or areas without faults are engaged. 

If a connection attempt with a 

marked device or area is then successful, 

the disturbance marking will be 

cancelled. 

Disturbance marking can be initiated 

for, for example, the devices and store 

areas included in a disturbed connection. 

Disturbance marking is also 

obtained for breaks or shortcircuits on 

external lines in those cases where 

supervision is possible. This supervision 

is normally in the form of supervision of 

the current feeding and then only when 

it is a question of closed circuit current. 

Aids 

ASB 100 is designed to permit a certain 

amount of communication with the 

system from the units that are always

Technical data 

Capacity 

Number of extensions 40 100 

Trunk lines incl. junction 

lines 12 24 

Local junctors 5 10 

Tone senders 3 6 

Operators 1 1 

Dimensioned for 0.17 erlangs with a congestion 

of 0.01 and 20-40% internal traffic. 

Cabinet Height Width Depth 

mm mm mm 

40 extensions 1068 600 300 

100 extensions 1800 600 300 

Telephone sets with dial for 10 or 16 Hz and 

the pulse ratio 30/70-50/ 

50; 

with push-button set for 

tone frequency key sending 

in accordance with CCITT 

Current feeding 2\400 ohms 

Loop resistance max. 1800 ohms for extension 

lines, including the 

telephone set, max. 1000 

ohms for exchange lines 

Leakage resistance min. 40 kohms 

Attenuation 0.8 dB on exter- 1 

nal circuits 

7 dB on internal 

circuits 

at8Q0Hz 

Crosstalk attenuation min. 80 dB at 1100 Hz 

Numbering two or three-digit extension 

numbers 

Power feeding 110/127/220/230/240 V a.c, 

50/60 Hz or 42- 54 V da, 

max. power consumption 

250 W 

Environment +5° to +40°C ambient temperature 

20-80 % relative humidity 

connected to the exchange, i.e. telephone 

sets and the operator's console 

Thus, for example, data concerning test 

connections can be programmed from a 

push-button telephone and most of the 

administrative data for the exchange, 

such as classes of service and 

abbreviated numbers, can be programmed 

from the operator's console. 

It is thus always possible to administer 

the exchange and carry out simple fault 

localization without having to introduce 

extra equipment. However, it is possible 

to connect an I/O device of standard 

type to the exchange when large 

quantities of data have to be fed in, for 

example when the exchange is put into 

operation or when advanced test and 

fault localization programs are run. For 

this purpose the exchange is equipped 

with a terminal outlet with a standardized 

interface in accordance with 

CCITT V24. A portable typewriter terminal 

is normally connected, but a display 

terminal can be used instead. Remote 

communication via modems is also possible. 

Normally the I/O function is not permanently 

connected, but is introduced in 

the system when required by inserting 

the necessary memory and interface 

boards. 

The I/O device can be used for: 

— programming of system data 

— initiation of test programs 

— printout of the results of test programs 

— printout of devices with disturbance 

marking 

19 

— printout of busy, blocked or test 

marked devices 

- printout of traffic recording data. 

Fault localization 

Fault localization in ASB 100 can be carried 

out either by means of test connections 

or program-controlled tests. 

Test connections are programmed from 

a normal push-button telephone or from 

the I/O device. 

Program controlled tests are carried out 

from the I/O device with the aid of special 

test programs. The boards with 

these can either be permanantly connected 

in the exchange or plugged in 

when required. They permit quick 

localization of faults down to the printed 

board assembly level. 

The tests can be carried out without disturbing 

the normal operation of the exchange. 

Command language 

Aspecial command language is used for 

communication with ASB 100 from the 

typewriter terminal. A command consists 

of a command word and in certain 

cases a parameter part where the 

parameters are separated by colons. 

The command word consists of a 

mnemonic combination of five letters, 

where the two first letters define the 

function, the next two define the subgroup 

within this function and the last 

letter defines the order that is to be carried 

out.

Field Trial with Common Channel 

Signalling 

Henning Andersen and Villy K. Pedersen 

The Danish telephone company Jydsk Telefon A/S, JTAS, and LM Ericsson have in 

close collaboration carried out a field trial with common channel signalling, CCS, in 

Denmark. The trial took place in the Mundelstrup telephone exchange, which belongs 

to Arhus local exchange area. The primary objective was to investigate how 

well the existing local exchange system could be adapted to common channel 

signalling, in accordance with CCITT system No. 6, but restricted to the register 

signals. The existing system originally consisted of the LM Ericsson crossbar 

system ARF 100, which was modernised to ARE 11 through the introduction of ANA 

30\ 

The trial provided excellent opportunities for assessing if and when it would be 

suitable to introduce common channel signalling in the network of JTAS. It can then 

be a question of either system No. 6 or its planned successor, system No. 7, for 

which CCITT is now preparing specifications. 

The article gives a short description of signalling system No. 6. The structure and 

function of the field trial model are then described, after which the results of the trial 

are evaluated. Finally there is some mention of the future plans for CCS. 

Around 1970 plans were begun to introduce 

PCM systems and, with the aid of 

ANA 30, stored program control in the 

Arhus local exchange area. In connection 

with this there was a desire to investigate 

what the technical and financial 

consequences would be of conforming 

to the latest developments in 

the signalling field. JTAS therefore decided 

that a field trial should be carried 

out. 

The work was undertaken by a working 

group, with members from JTAS and LM 

Ericsson. Both parties contributed to 

the good results of the trial, which lasted 

from September 1974 to November 

1976. 

UDC621 395 631 

An article in an earlier issue of Ericsson 

Review described how field trials had 

been carried out with signalling system 

No. 6for international telephone circuits 

connected up via an international transit 

exchange AKE 13 in Australia 2 . The final 

CCITT specifications were prepared taking 

into consideration the experience 

gained from these trials. 

However, common channel signalling is 

not reserved for international circuits 

only, but can be used at all levels in the 

telephone network. Thus variants of 

system No. 6 have become widespread 

in the national networks in the USA and 

Japan. 

Characteristics of signalling 

system No. 6 

Signalling system No. 6 has been developed 

entirely within CCITT, and is described 

in the Orange Book, Vol. VI. 2 3 . A 

summary of the contents is given below. 

The system can be used on all types of 

international and national circuits, including 

multi-exchange local networks. 

However, in national applications certain 

additional signals are required. The 

system is primarily intended for stored 

program controlled exchanges. It is a 

link-by-link system, which means that 

the signals are regenerated in each 

fig. 1 

Channel-associated signalling 

FUR Outgoing junction line relay set with line signalling 

FIR Incoming |unctlon line relay set with line signalling 

" ^ Register signalling

21 

HENNING ANDERSEN 

VILLYK. PEDERSEN 

Jydsk Teleton A/S, Arhus. Denmark 

Fig. 3 

The four types of bit pairs and the corresponding 

phase shift angle of the carrier 

transit point before being transferred 

from one link to another. 

In older signalling systems there is always 

an unambiguous physical connection 

between each speech connection 

and the signals associated with it. Consequently 

this signalling method is called 

channel-associated signalling, fig. 1. 

The signals are usually transmitted in 

the speech channel or in a band that belongs 

to the channel but lies outside the 

transmitted speech band. In signalling 

system No. 6, on the other hand, a separate 

signalling channel is used, which is 

common for a large number of speech 

channels, and which transmits the signals 

required for all these channels. This 

method is therefore called common 

channel signalling, fig. 2. 

Thus a signal that is transmitted in the 

common signalling channel is not 

physically tied to a particular speech 

channel, and hence each signal must be 

provided with a speech channel label 

that indicates the speech channel to 

which the signal belongs. 

All channel-associated signalling systems 

require that the in-band signals are 

transmitted without errors in both directions 

if it is to be possible to establish a 

connection. This provides an automatic 

check that there are no faults in the 

speech path before the call is set up. 

Since the signals in system No. 6 are 

transmitted over a separate channel it is 

possible that everything functions normally 

except the speech transmission. 

Consequently with this system the 

speech paths are checked with a tone of 

2000 ±20 Hz before the call is set up. 

The system is designed primarily for 

analogue transmission systems, since it 

was assumed during the development of 

the system that this type of transmission 

would be predominant on international 

lines during the estimated life of the 

system. However, a modified version of 

the system can be used for digital 

transmission systems (PCM). 

Analogue version 

In the analogue version a data link is 

used that consists of a normal 4-wire 

circuit for telephony. The transmission 

speed is 2400 bits/second. Both ends of 

the data link are connected to so-called 

four-phase modems, with the binary 

data signals grouped in bit pairs (dibits) 

(00, 01, 11 and 10), where each pair corresponds 

to one of the four phase positions 

of the signal carrier. The pair that is 

the next to be transmitted initiates a shift 

to the phase angle required for sending 

the information, fig. 3. 

There is a constant bit stream in both 

directions over the data link. It is filled 

with non-informative signals, so-called 

Fig. 2 

Common channel signalling in accordance with 

CCITT system No. 6 

© The common signalling channel is a data link 

consisting of a normal 4-wire circuit 

@ Four-phase modem for the transmission of bit 

pairs (dibits)

Fig. 4 

Signal flow 

(T) 

Includes 11 bits that state which signals were 

received correct and faulty respectively 

Fig. 5 

Example of a star-shaped signalling network 

with two signal transfer points STP1 and STP2 

^—• Alternative speech routes between A and B 

~— Speech paths for STP1 

^ - Speech paths for STP2 

O Exchange 

Signal transfer point STP 

A Local exchange A 

B Local exchange B 

Ti Local transit exchange 1 

T2 Local transit exchange 2 

synchronization units (SYU), when there 

is no need of real signal information. 

The bit stream is divided into signal 

units (SU) consisting of 28 bits, of which 

the last eight are check bits, fig. 4. With 

the aid of these the receiving signal 

terminal decides whether the received 

signal unit is correct or faulty. 

Twelve signal units form a block, with 

the twelfth unit consisting of an acknowledgement 

unit (ACU). The information 

from the check bits is transferred to 

ACU, where a decision is made as to 

which signal elements, if any, are to be 

returned because of faulty transmission. 

The previously mentioned synchronization 

unit (SYU) contains a determined 

bit pattern. Apart from its use as a filler 

to make up a continuous bit stream, SYU 

is used the first time the data link is 

started up. Only synchronization and 

acknowledgement signals are then sent 

until the signal terminals at both ends 

are synchronized at bit, signalling unit 

and block level. 

Digital version 

In the digital (PCM) version of signalling 

system No. 6 the following bit rates are 

used: 

- bit rates of 4 and 56 kbit/s for 30/32- 

channel PCM. This is the European 

standard and the signal bit stream is 

transmitted in a special time slot (No. 

16) 

- a bit rate of 4 kbit/s for 24-channel 

PCM systems, which are widely used 

in the USA and Japan. 

Some facts concerning 

the field trial 

The following basic facts are given in 

order to make it easier to understand 

how the field trial model in its entirety 

functions. 

A SPC exchange of type ARE 11 always 

contains a control system ANA 30. When 

an ARF 10 exchange is modernised by 

the inclusion of ANA 30 it also becomes 

a SPC exchange, and its type designation 

is changed to ARE 11. 

The normal version of ARE 11 with ANA 

30 and the associated software have 

been described in two articles in Ericsson 

Review 4-5 . 

Special processor functions are added 

for common channel signalling 

The normal version of ARE 11 contains 

two types of processors, namely traffic 

control processors TCP and operation 

and maintenance processors OMP. 

Signalling system No. 6 requires the 

addition of a common channel signalling 

processor CCP in the terminal exchange 

and a signal transfer point processor 

SPP for STP functions. All processor 

types consist of the same hardware. 

Thus if there is unused capacity in 

a TCP it can be provided with the required 

software and also used as CCP. 

Star-shaped signalling network 

In spite of the mesh-shape of the speech 

network in the Arhus area, the field trials 

were optimized for a star-shaped signalling 

network with two signal transfer 

points, STP1 and STP2, in accordance 

with the example in fig. 5. Each STP is 

normally situated in or near a telephone 

exchange, which does not need to be 

included in the speech connection but 

which transfers the CCS signals. 

Each exchange must then have at least 

one signalling channel to each STP, and 

the signalling traffic is usually divided 

equally between these channels (load 

sharing). This saves time since the queuing 

time is reduced, and also provides 

greater reliability because of the duplication. 

If a fault occurs in one channel, 

the signalling in question is transferred 

to the other channel. 

The maximum number of speech 

channels 

There is an upper limit to how many 

speech channels a signalling channel 

can serve, since it can only transmit a 

limited number of signals per unit of 

time. This limit is dependent on, for 

example, the average seizure time of the 

speech channel, and thus it varies in different 

applications. In the Mundelstrup 

trial, where the signalling channel could 

only transmit register signals, a signalling 

channel served approximately 1960 

speech circuits, which would be reduced 

to 980 if the line signals were also 

included. 

Different signalling possibilities 

The analogue version of the signalling 

svstem was used for the field trial, but

23 

signalling was to be carried out over the 

speech wires in accordance with the existing 

principles. The speech transmission 

paths were thereby automatically 

checked, and hence the continuity 

check of the speech paths recommended 

by CCITT could be omitted in 

the field trial. 

Fig. 6 

Schematic picture of the Mundelstrup field trial 

equipment with a signal transfer point STP and 

signalling conditions that are typical for Arhus 

local exchange area 

Speech circuit A - B - C 

Signalling circuit A- B and the designation forcertain 

signals sent via it 

Signalling circuit B — C and the designation tor certain 

signals sent via it 

Fig. 7 

Block diagram for the field trial equipment in 

Mundelstrup with common channel signalling 

CCP 

SPP 

GV-KME 

DC-I 

Common channel signalling processor 

Signal transfer processor 

Code receiver 

Interlace equipment 

Equipment that has been added tor the 

— field trial 

Equipment that has been changed for the 

field trial 

the software was also prepared for the 

digital version with a transmission 

speed of 4 kbit/s. Facilities were also 

provided for conversion between common 

channel and d.c. code signalling, 

as well as for connecting via two transit 

exchanges. 

As has been mentioned above, for this 

project it was decided that the line 

Traffic cases 

The field trial equipment consisted of a 

signalling link, with both ends connected 

to a processor in ANA 30 via a 

signal terminal. Another of the exchange 

processors could be connected 

in to and disconnected from the signalling 

link, and was thus able to function 

as a signal transfer point STP when required. 

In this way it was possible to set 

up connectionsthat represented signalling 

circuits within the whole of the Arhus 

local exchange area, including 

connection to transit exchange AKE 13. 

Fig. 6 shows how a local transit circuit 

from A to C is set up with signalling via 

STP.

Fig. 8 

Block diagram for the signal terminal 

TCP 

CCP 

Traffic control processor 


Description of the special 

equipment for CCS 

Fig. 7, which contains a block diagram 

of the whole of the Mundelstrup exchange, 

indicates the equipment that 

was added for the field trial. Small 

changes in ANA 30 were also carried 

out. 

Signal terminal 

A signal terminal is shown in fig. 11. It 

serves as an interface stage between a 

processor and a modem for 2400 bit/s. It 

is used both in the local exchange and 

the signal transfer point, STP, and contains, 

among other things, transmitting 

and receiving bufferfunctionsfortaking 

up the difference in speed between processor 

and modem, fig. 8. 


CCP 

CCP generates CCS signals under the 

control of a traffic control processor 

TCP (or the operation and maintenance 

processor OMP). These signals are 

transmitted to a signal terminal in a predetermined 

order of priority. CCP also 

receives and analyzes signals from the 

signal terminal and distributes them to 

the TCP or the OMP concerned, fig. 9. 

Communication between them takes 

place via the translation store TRS. 

CCP also generates synchronization 

and acknowledgement signals, and retransmits 

the signals that are found to 

be faulty. 

15 new programs have been developed 

for the above-mentioned purposes, and 

a number of data pages have also been 

allocated to them. 

Because of the importance of its functions 

CCP has been duplicated. In implementing 

this, the principle has been 

applied that no information shall be lost 

when changing over from theworkingto 

the standby processor. 

Additions to the existing ANA 30 

system 

FUR and FIR labels have been introduced 

in the existing ANA 30 equipment 

in the Mundelstrup exchange. It should 

be mentioned, however, that the latest 

version of ANA30includesthis possibility 

as a standard feature. 

The FUR label identifies the selected device 

in a group of 20 outputs in the first 

group selector (IGV) stage. Its code receiver 

GV-KME stores this label, which 

is then read out by TCP (fig. 7). 

The label of a FIR call is given by the 

register finder inlet (one of 64). It is 

transmitted by the interface equipment 

DCI-one per register finder marker 

RSM-to the identifier IDS, from which 

TCO reads the RSM number and FIR 

label. 

Fig. 9 

Communication between CCP and TCP is handled 

by the translation store TRS 

CCP 

TCP 

TRS 


Traffic control processor 

Translation store

25 

Fig. 10 

Simplified block diagram for the setting up of i 

transit connection with signalling via a signal 

transfer point, STP. The signal terminals and 

4-phase modems are not shown 

^ Call with conventional line signalling 

»- Initial address message, IAM 

Subsequent address messages, SAM 

», Free B-subscriber 

Signal transfer processor SPP 

SPP works in accordance with the same 

principles as CCP. Thus the signals go 

from SPP in a certain order of priority to 

a signal terminal. When receiving, SPP 

reads off the incoming signals in the 

signal terminal. These signals are 

analysed. The ones that are to be sent on 

gettheirlinkand "band" numbers translated 

in a translation table. By band 

number is meant the seven most 

significant bits in the speech channel 

label. It has thereby been possible to reduce 

the size of the table. 

SPP is duplicated in the same way as 

CPP. 

Carrying out the field trial 

The following equipment was used for 

the field trial: 

— Control system ANA 30 with two processors 

TCP supplemented with CCP 

and STP functions, an OMP, a SCS 

and a TRS 

— Interworking equipment between the 

switching equipment and the control 

system, model Arhus 

— Subscriber (SL) stage, 1000 multiple 

positions 

— Group selector (GV) stage, 80 inlets 

— SR, LKR, FUR and FIR. 

With this limited range of equipment it 

was not possible to generate sufficient 

traffic for test connections. Simulated 

traffic, which was generated by a special 

program in OMP, was therefore used to 

increase the signal traffic by 0.2 — 1 

erlang. 

The real traffic was superposed on the 

simulated traffic and was measured by a 

special program in CCP and SPP respectively. 

The program was handled in 

free time slots. The measurements were 

used to determine the transfer times between 

buffers for the signals passed in 

the system. From the results it was possible 

to evaluate the system signalling 

times and to compare these with the 

CCITT specification. 

The field trial covered all traffic cases 

that represent normal signalling conditions 

in the Arhus local network, including 

transit connection and also connections 

to AKE 13 in the Slet exchange and 

STP. 

However, it was not possible to carry out 

certain special tests because of the limited 

amount of equipment. The most 

important of the tests that could not be 

carried out was the changeover from 

STP1 to STP2.

26 

Simplified description of the 

setting up of a connection 

A brief account is given here of how a 

transit connection is set up with signalling 

via a separate signal transfer point 

STP, figs. 6 and 10. The call attempt 

starts with a signal transfer unit STU-L 

being connected in and receiving digits. 

After three digits a FUR is selected under 

the control of TCP. The corresponding 

FIR in exchange B is called by means 

of conventional line signalling. 

The TCP in exchange A reads the FUR 

label. It transfers the first three digits 

and the speech channel label to CCP, 

which then generates the initial address 

message, IAM. This signal is sent via the 

signalling channel to STP, where it is 

analyzed and the label is translated. The 

signal is then sent to exchange B, where 

it is analyzed by TCP on the initiative of 

the called FIR, which has been connected 

to a signal translation unit STU-I. 

If the call turns out to be to exchange C, 

a FUR is selected, which calls the corresponding 

FIR in exchange C. In the 

normal way the TCP in exchange B 

transmits a signal to CCP, giving the 

speech channel label of the selected 

FUR. CCP then sends IAM to STP, where 

it is analyzed and the label is translated 

before being sent on to exchange C. 

In exchange C TCP decides that the call 

in question is a terminating one and 

waits for the remaining digits. When 

these have been received in exchange 

A and transferred from TCP to CCP, the 

latter generates a subsequent address 

message SAM and sends it to STP. 

The procedure is then the same as for 

the initial address message. Thus SAM 

is transmitted via STP-^B->STP-^C, 

with translation of the speech channel 

label in STP and B. 

When the remaining digits have been 

received in exchange C the switching 

stage is set up and the line state of the B 

subscriber is determined. If the line is 

free, TCP sends the appropriate signal 

to CCP, which then sends the free signal 

and speech channel label for the FIR in 

question in the return direction via C-* 

STP-^B^STP-^A. 

This free signal results in the speech 

circuit being through-connected at 

these three exchanges. 

Result 

The field trial has provided valuable experience 

of the CCS system and its 

adaption to the national network at the 

local exchange level. The trial has 

shown that control system ANA 30 is 

Fig. 11 

Signal terminal

Fig. 12 

The principle for common transmission equipment 

and Individual equipment tor each type ot 

communication with the CCITT signalling system 

No. 7 

References 

1. Meland, F. and Rishoj, E.: Crossbar 

Exchanges in Arhus become SPC 

Exchanges. Ericsson Rev. 54 

(1977):2, pp. 86-89. 

2. Hinwood, J. D. and Clark, D. W.: 

Field Trial of CCITT Signalling 

System using AKE13. Ericsson Rev. 

49 (1972):4, pp. 124-138. 

3. CCITT Orange Book, Vol. Vl.2. 

4. Morlinger, R. and Viktorsson, O.: 

ARE 11 -System Description. Ericsson 

Rev. 54 (1977):2, pp. 67-76. 

5. Hemre, A. and Hagard, G.: The 

Software and Its Handling in ARE 

System. Ericsson Rev. 54 (1977):2, 

pp. 77-85. 

6. Andersson, B. et al.: ARE Systems 

in Modern Networks. Ericsson Rev. 

54(1977):2, pp. 54-66. 

very suitable for adaption to CCS signalling 

and for STP functions. 

With direct signalling between two exchanges 

the analogue version of system 

No. 6 gives a signalling time that is of the 

same order of magnitude as MFC and 

d.c. code signalling. In the case of transit 

traffic the link-by-link principle is 

used for CCS, whereas the faster endto-end 

signalling is used for MFC and 

d.c. code signalling. Thus in this case 

the signalling time is longer for the CCS 

analogue version than the other two 

methods. This becomes more apparent 

when the connection is made via two 

transit points with signalling via STP. 

However, it is possible to start the setting 

up process earlier, whereby the wait 

for the ringing signal —the post dialling 

delay — is reduced to a satisfactory level. 

The field trial has not, however, provided 

sufficient basic data for reliable 

cost calculations, and thus it has not 

been possible to make economic comparisons 

between a CCS and a MFC 

network. 

Plans for the future 

Signalling system No. 6 is now being introduced 

on many international telephone 

circuits. The interest in CCS has 

grown also in other parts of the telecommunications 

field, which has meant 

that the fundamentals of the system are 

having to be reconsidered. 

Thus it can no longer be assumed that 

CCS must only be suitable for international 

circuits, where the cost of the 

signalling equipment is not decisive. 

Now it must also be suitable for the national 

network, where the cost aspect is 

of greater importance. 

Since PCM is now beginning to be an 

economic form of transmission even for 

long distances, it is possible to use a 64 

kbit/s digital channel for CCS. This 

means that the signalling rate can be increased, 

and furthermore the analogue 

modem will not be required. 

Finally the introduction of the digital 

group selector is now imminent. As was 

made clear in a previous article in Ericsson 

Review 6 this can be done with 

advantage even in an existing ARE 

network. This development will lead to a 

changed network structure and also the 

introduction of concentrators around 

the new exchanges. Moreover measures 

will then be taken to prepare for an integration 

of different forms of communication, 

such as telephony, telex, 

data, gentex, and also network management, 

maintenance etc. 

Consequently CCITT is now in the process 

of preparing a new CCITT system, 

No. 7. It will contain a message transfer 

part that is common for all forms of 

communication, and which will constitute 

the actual common signalling 

channel. Individual parts, fig. 12, foreach 

communication form will then be connected 

to the ends of the common message 

transfer part. 

The specifications for this signalling 

system are expected to be completed 

around 1980. The main features are 

already known, however, and thus it is 

possible to plan how the system should 

be used in principle. It is even considered 

that it will be possible to use the 

transmission principles of system No. 7 

between concentrators and the parent 

exchange.

60 MHz Coaxial Cable System for 

10800 Channels 

Per-Alrik Hallberg, Thorwald Lundmark and Luigi Manes 

By extending the band transmitted over coaxial cables to 4-60 MHz it is possible 

to transmit 10800 channels, in the form of twelve supermastergroups or six television 

channels. LM Ericsson in collaboration with the Italian company FATME, 

which is a member of the Ericsson Group, have developed a 60 MHz system for 

coaxial cables, ZAX 10800. The equipment is manufactured in the same construction 

practice as the 4 MHz and 12 MHZ coaxial cable systems. The article gives a 

description of the equipment and also the result of a field trial in Italy. 

with six tubes is 32 400 channels and the 

capacity of a cable with twelve tubes is 

64 800 channels. This is a very considerable 

capacity, which it is rarely desirable 

to exceed, among other reasons because 

of the consequences of a cable 

break. In the case of coaxial cable of 

small diameter, however, the repeater 

distance will be very short which means 

more noise than is desirable. 

UDC621 315212 

Fig. 1 

Equipment for sending and receiving in the line 

terminal 

COM Combiner 

FEQ Fixed equalizer 

PE Pre-emphasis network 

PEQ Pre-equallzer 

LBO Line building-out network 

PC Pilot combiner 

PFU Remote power feeding unit 

FLO Fault location oscillator 

DE De-emphasis network 

EEG Echo equalizer 

SEP Separator 

The growth of the long-distance traffic 

creates a demand for greater traffic capacity. 

Since the cost of electronic 

equipment is only a fraction of the cost 

of cables, existing coaxial cables have 

naturally been utilized as far as is technically 

and practically possible. A limiting 

factor, however, is that the transmission 

data of the cable may deviate 

so much from the calculated data that 

it is difficult to obtain sufficiently accurate 

attenuation equalization. 

Most existing coaxial cables of normal 

diameter are suitable for transmission 

of 60 MHz and the cost per channel kilometre 

is low even in the case of new 

cables because of the high transmission 

capacity. The balance between cable 

cost and repeater cost is better than in 

the case of other 4-wire coaxial systems. 

The transmission capacity of a cable 

The 60 MHz coaxial cable system for 

10800 channels, ZAX 10800, consists of 

terminal equipment and line repeaters. 

The system is in the LM Ericsson tradition 

in this field as regards reliability, 

maintainability and mechanical construction 

practice. 

The terminal equipment is described 

first, then the different types of line repeaters 

and the power feeding equipment, 

followed by regulation, equalization 

and fault location. The mechanical 

construction is described briefly and 

finally the results from a trial route are 

presented. 

Terminal equipment 

The function of the terminal equipment 

is to adapt the line band from the multiplex 

equipment to what is needed for 

transmission over the line, see fig. 1.

PER-ALRIK HALLBERG 

THORWALD LUNDMARK 

Transmission Division 

Telefonaktiebolaget LM Ericsson 

LUIGI MANES 

FATME, Rome 

Fig. 2 

Line repeater with fixed gain 

Fig. 3 

The basic design of the pre-amplifier. In a 

regulating line repeater a thermistor T is used 

and in a non-regulating repeater a resistor R that 

corresponds to a certain gain. RN is a regulating 

network. 

Fig. 4 

The basic design of the power amplifier 

Send direction 

On the send side the necessary regulating 

pilots 61160, 22372 and 4287 kHz 

are added and the upper part of the 

band is pre-emphasized. It may also be 

necessary to include stop filters to suppress 

disturbances in the line band at 

the pilot frequencies, The frequency 

comparison pilot 4200 kHz can be fed 

into the equipment at a level of 0 dBm 

or -7 dBm. It is fed in together with the 

other pilots. 

The fault location frequencies are generated, 

with a unique frequency for each 

line repeater, and are supervised at the 

receiving terminal. The received frequencies 

can be loop connected at one 

of the terminals so that all supervision 

can be carried out from the other terminal. 

The attenuation in the send side station 

cable can be equalized by up to 3.5 dB 

in an active equalizer, which corresponds 

to a line length of approximately 

30 m at 60 MHz. The equalizer is also 

equipped with two similar inputs, so 

that measurements can be carried out 

with additional measuring frequencies 

during traffic. A corresponding facility is 

provided at the output in the receive direction. 

Receive direction 

The main task of the receive side is to 

equalize and regulate the received line 

band. This is done with the aid of fixed 

equalizers, an echo equalizer and regulation 

equipment related to the two 

extra pilots 22372 and 4287 kHz. Regulation 

with the aid of the main pilot 

61160 kHz takes place in the terminal 

repeater, where de-emphasis to flat (frequency 

independent) level also takes 

place. The pilots are suppressed by filters 

with 50 dB attenuation. 

The frequency comparison pilot 4200 

kHz, which is only transmitted over the 

system and thus is not used for regulation 

purposes like the other pilots, is extracted 

in a flat amplifier and is fed to 

the frequency control equipment in the 

station. The flat amplifier also compensates 

for the basic loss of the passive 

stop filters, and feeds the fault location 

frequencies both to the loop connection 

and to a test point on the front of 

the unit, where they can be checked 

with the aid of an external instrument. 

Line repeaters 

The line repeater is available in three 

variants: one with fixed gain, one with 

pilot regulation and one for use in the 

terminal. 

All three have the same mechanical design 

and each is a compact unit that includes 

the equipment for both directions 

of transmission. 

Line repeater with fixed gain 

The simplest version of the line repeater 

has fixed gain. The main parts, fig. 2, 

for one direction are 

— amplifier 

— pre-equalizer 

— power separation filters 

— line building-out network 

and common for both directions are 

— zener diodes 

— fault location oscillator. 

The amplifier part consists of two 2- 

stage amplifiers: one pre-amplifier with 

low thermal noise and one power amplifier 

with fixed gain and very low harmonic 

distortion, figs. 3 and 4. Together 

they give a gain of 28.5 dB, which can be 

varied over the range ±3 dB, by changing 

a resistor in the feedback network. 

A transformer is placed between the two 

amplifiers in order to provide phase inversion 

in each line repeater. In this way 

a more favourable addition of the noise 

contributions from the individual repeaters 

is obtained 6 . 

Fig. 5 

The principle tor power feeding the line repeaters. 

31 -34 are the different connection points. Every 

other line repeater is changed over so that the 

feeding direction is always changed. This 

balances the power feeding relative to earth, 

which also leads to a reduction of the hum 

modulation.

8 

30 

Fig. 7 

Line repeater with pilot regulation 

Both amplifiers are constructed in the 

hybrid technique, and in each of them 

thick film technique is used for the active 

parts and most of the feedback network. 

This gives a short feedback loop 

and a small phase shift. 

A conventional pre-equalizer in the preamplifier 

shapes the gain curve at low 

frequencies and power separation filters 

at the input and output separate and 

combine the HF signals and the power 

feeding. A line building-out network 

provides simulated cable attenuation of 

up to 22 dB, i.e. almost a whole repeater 

section. The line building-out network 

can be placed in any line repeater. 

Parallel feeding is used for the power 

feeding of the line repeaters in such a 

way that one zener diode feeds both 

transmission directions, but with a separate 

diode for the pre-amplifier and 

the power amplifier respectively, fig. 6. 

This feeding method requires double 

the current but only half the voltage of 

series feeding, and hence almost twice 

the number of line repeaters can be fed 

with this method. This is particularly desirable 

in a 60 MHz system since the 

distance between the line repeaters is 

short. 

The line repeaters are well protected 

against external electrical disturbances 

taken up by the cable, such as lightning 

pulses. Gas discharge tubes with a striking 

voltage of 1400 V are provided at the 

input and output of the repeaters, between 

the inner conductor and earth. 

The limit frequencies for the power separation 

filters are chosen so that as 

little as possible of the energy in the 

lightning pulse gets into the amplifier 

part. The input and output of the amplifier 

part are also provided with diode 

chains and each transistor is protected 

by a base-emitter diode. Thus a whole 

series of protective circuits combine to 

give the greatest possible operational 

reliability. 

Line repeater with pilot regulation 

The line repeater with pilot regulation 

has the same construction as the repeater 

with fixed gain, except that a regulating 

circuit has been added. This 

circuit consists of a pilot receiver equipped 

with a digital memory and a thermistor. 

The gain is regulated automatically 

with the aid of the 61160 kHz pilot 

so that the level at the output of the line 

repeater is always held at the nominal 

value, fig. 7. 

The regulation process is as follows: 

The pilot signal is extracted at the output 

of the power amplifier with the aid 

of a crystal filter and is then amplified 

and rectified. The pilot voltage thus obtained 

is compared with a constant d.c. 

voltage in an operational amplifier. The 

voltage difference determines the 

amount of current through an NTC thermistor 

placed in the series branch of the 

pre-amplifier feedback network. 

If the pilot fails, a digital memory takes 

over the control of the thermistor with 

the same current that existed immediately 

before the loss of the pilot. The 

gain conditions that applied will then be 

maintained until the pilot returns. The 

memory circuit consists of an 8-bit shift 

register, with the aid of which the thermistor 

current can be reproduced so 

that the regulation range is divided into 

steps of 2 mB. 

The regulation range at 61160 kHz is 

±3 dB, of which approximately ±2 dB 

is used for variations in the cable at- 

Fig. 6 

One direction ot the regulating line repeater. The 

zener diodes teed the corresponding part in the 

other direction 

PRA Pre-amplifier 

POA Power amplifier 

PR Pilot receiver

31 

Fig. 9 

Regulation range for the main regulating pilot 

61160 kHz 

tenuation caused by temperature 

changes, and ±1 dB for variations in 

length when installing the regulating 

line repeaters, fig. 9. All gain variation 

as a result of the regulation takes place 

in the pre-amplifier. 

Terminal repeater 

The levels between the cable side and 

the line terminating equipment are adjusted 

with the aid of a terminal repeater, 

which on the send side has the same 

design as a line repeater with fixed gain 

and on the receive side the same design 

as a repeater with pilot regulation. The 

transmission band is thereby regulated 

before equalization. A de-emphasis network 

on the output gives the desired flat 

level. 

An alarm circuit senses the level of the 

61160 kHz pilot at the output of the 

power amplifier, and if the deviation 

after regulation exceeds a preset value, 

which can be set to ±0.7, ±1.2 or ±1.7 

dB, an alarm is obtained. A separate 

outlet is provided, to which a recorder 

can be connected for continuously 

monitoring the pilot level. 

In order to avoid having too high a 

voltage in the terminal bay the terminal 

repeater is not fed with power from the 

remote power feeding system that feeds 

the remaining line repeaters. The terminal 

repeater is instead fed from a local 

21 V d.c. converter. 

Power feeding 

The equipment can be fed with power 

from a 24 V, 36 V, 48 V or 60 V station 

battery. It can also be fed from the mains 

via a mains rectifier that gives a d.c. 

voltage of 41-72 V from 110 V or 220 V 

a.c. The mains frequency is allowed to 

vary between 45 and 65 Hz. The output 

power from the rectifier is 440 W. 

Fig. 8 

Line repeater with amplifier part, pilot receiver 

and power separation filters

32 

The terminal equipment for two fully 

equipped systems can be mounted in 

one bay. The two systems are quite independent 

of each other, even as regards 

power feeding. 

Power feeding of the line repeaters 

The line repeaters are power fed from 

a remote power feeding unit placed in 

the terminal bay. The unit gives a constant 

direct current of 290 mA and an 

output voltage of 20-1200 V. When 

the system is fed from a station battery 

and every fourth line repeater is regulating, 

up to 47 repeaters can be fed 

from the unit, which gives a distance of 

147 km between two power-feeding stations, 

fig. 12. The given maximum values 

for current and voltage are selected with 

regard to personal safety when handling 

the equipment. 

The direct current is fed from the unit 

via a separation filter in a power feeding 

adapter to the inner conductor of the 

coaxial tube (fig. 1). Each line repeater 

is then fed in the way shown in figs. 2 

and 7. After the last repeater in the 

power feeding chain there is a power 

looping adapter that takes the current 

over to the opposite transmission direction 

and back to the remote power 

feeding unit. 

To ensure reliable operation of the 

whole system, including the line repeaters, 

the unit is equipped with supervision 

and alarm circuits for each of the 

following fault conditions: 

— current increase 

— current decrease 

— unbalance of the feeding voltage 

— loss of battery voltage. 

The different alarm conditions are indicated 

by light emitting diodes on the 

front of the unit. A common outlet for 

the supervisory circuits can be connected 

to the station alarm for indication 

of a faulty unit. 

For each of the first three supervisory 

circuits it is possible to strap so that 

when the corresponding fault condition 

arises the unit is automatically disconnected 

and its output voltage and current 

are brought to zero. In addition to 

the supervision described above the 

unit is provided with an overvoltage protection 

that always disconnects the 

unit when it operates. This occurs, for 

example, in the case of a cable break 

because the unit is of the constant current 

type and then tries to feed out 290 

mA by raising the voltage. 

The unit contains two instruments, one 

for current and one for voltage measurement. 

A potentiometer, accessible 

from the front, is used to adjust the outgoing 

current to 290 mA. It is easy to 

Fig. 10 

Adjusting the gain curve

Fig. 12 

Power feeding of the line repeaters. A power 

looping adapter is placed after the last repeater 

in the feeding chain. 

Fig. 13 

Regulation range for the two pilot regulated 

equalizers 22372 kHz and 4287 kHz 

determine whether there is any unbalance 

because it is possible to measure 

the voltage between each inner conductor 

and earth. The circuit breaker for 

the unit is key controlled, and it is thus 

possible to prevent restarts, for example 

during maintenance work. 

Power feeding of the bay equipment 

The units in the line terminating equipment 

are combined to form a shelf 

stack, those which are active being 

power fed from two 12 Vd.c. converters 

of 25 W each. One converter is used for 

the units in the send direction and the 

other for the units in the receive direction. 

The 21 V d.c. converter of 30 W which 

feeds the terminal repeater is also placed 

in the shelf stack. The speaker circuit 

shelf is provided with d.c. converters 

of its own. 

Level regulation 

Level variations along the line are caused 

by temperature changes in the cable. 

The cable attenuation varies approximately 

0.2 % per °C. The level variations 

are mainly seasonal and are compensated 

automatically by regulating line repeaters 

along the line and, if necessary, 

also by pilot regulated equalizers in the 

receive side of the terminal equipment. 

The main regulating pilot 61160 kHz is 

active in the regulating line amplifiers 

and the two extra pilots 22372 kHz and 

4287 kHz are active only in their respective 

equalizers. 

The regulation range varies over the frequency 

band, figs. 9 and 13. The range 

is ±3 dB at each pilot frequency. Usually 

it is sufficient to use single pilot regulation, 

i.e. only the main pilot 61160 

kHz, for the regulation of the system. 

The use of two additional pilots, i.e. 3- 

pilot regulation, is necessary only 

when the cable is exposed to large temperature 

variations or when the route is 

very long. For example, when the route 

contains an intermediate power feeding 

repeater station between the two terminals 

the use of 3-pilot regulation should 

be considered. 

It is sufficient to make every fourth line 

repeater along the line regulating as 

long as the variation in cable temperature 

does not exceed ±10°C. If the variations 

are greater than this, every third 

or every second repeater must be regulating. 

This situation arises when the 

cable follows a bridge or a tunnel, since 

it must then sometimes be run out in the 

open, and is then exposed to rapid and 

irregular temperature variations. 

Equalization of the line 

attenuation 

When the system is put into operation 

a curve is measured at the receiving terminal 

which shows how the level deviates 

from the expected value. This deviation 

is caused by the differences in the 

actual attenuation-frequency characteristic 

of the cable in relation to what had 

been anticipated. The resultant devia- 

Fig. 11 

Remote power feeding unit for feeding the line 

repeaters

Fig. 14 

Location of a faulty line repeater. If one direction 

is faulty in line repeater No. 4 only frequencies 

t s-f a are obtained at terminal B, whereas all frequencies 

f, — t e are obtained at terminal A 

tion over the route is eliminated by 

means of equalization. The equalization 

process is divded into coarse and 

fine equalization. 

The coarse equalization is carried out 

with fixed equalizers, one in the send 

direction for pre-equalization of the line 

and two in the receive direction for 

more accurate post-equalization. Each 

such device holds three correction networks. 

Theamount of equalization available 

in each direction of transmission is 

6dB. 

The fine equalization is carried out by 

means of what is called an echo equalizer, 

which is based on the use of a delay 

line. The device contains 30 outlets, 

each of which has a variation range of 

±3 dB. Adjustments are made with a 

potentiometer that is accessible at the 

front of the unit. A residual deviation 

curve can quickly be equalized with this 

equalizer. This equalizer can also be set 

up when the system is in service by 

using external test equipment and sending 

additional measuring frequencies 

over the system from the other terminal 

and measuring them. 

In addition to the equalization in the line 

terminal an equalization board can, if 

necessary, be included in each transmission 

direction in one of the non-regulating 

line repeaters. This board is designed 

as a fixed equalizer and the number 

required on a certain route will depend 

on how well the attenuation-frequency 

characteristic of the cable and 

the gain-frequency characteristic agree. 

To sum up it can be said that on short 

routes it is sufficient to have only fixed 

equalizers, or alternatively an echo 

equalizer, whereas on long routes both 

these aids are required and perhaps 

also some equalizer boards. The aim of 

the equalization is that the residual deviation 

curve for the route shall be within 

the limits of ±1 dB recommended 

byCCITT. 

Fault location 

Faulty line repeater 

It must be possible to locate a faulty line 

repeater rapidly and easily. For this purpose 

each repeater has been equipped 

with a simple crystal oscillator that generates 

an individual identification frequency, 

which is fed into both directions 

of transmission. The presence of 

the frequency can be checked with a selective 

level meter in the receiving terminal, 

and only the frequencies that 

emanate from the line repeaters after 

the faulty one will then be obtained, fig. 

14. The fault location frequencies lie at 

intervals of 2 kHz in the band 3640- 

4000 kHz. This makes it possible to supervise 

180 line repeaters, which corresponds 

to a homogeneous section of 

280 km. 

If the distant terminal station is unmanned 

the incoming fault location frequencies 

can be looped there and 

double modulated with the frequencies 

7400 and 7220 kHz and then sent back. 

Half the available band is then used, i.e. 

frequencies that lie in the band 3820- 

4000 kHz are shifted to 3640 -3820 kHz, 

whereby both transmission directions 

can be supervised from one and the 

same terminal. 

Another way of using the looping equipment 

is to send the modulated frequencies 

on in the same direction. A general 

equipment for supervision of the fault 

location frequencies has been developed 

for the 4, 12 and 60 MHz systems. 

Cable break 

The power feeding of the line repeaters 

is cut off immediately if the cable is 

broken, and thus the fault location 

Fig. 15 

Location of a cable break. The amount of current 

fed out indicates where along the route the break 

has occurred

35 

oscillators also cease operating. In order 

to find the break the output current 

from the remote power feeding unit is 

measured when a constant voltage of 

600 V is supplied to the line from this 

unit. Each line repeater contains a highohmic 

resistor between the two transmission 

directions, through which a 

small amount of current can flow. The 

current measuring instrument in the remote 

power feeding unit has a special 

scale for measuring this current. When 

installing the system it is easy to calibrate 

and obtain the scale readings that 

correspond to the different line repeaters, 

fig. 15. 

Mechanical construction 

and installation 

As may be seen from fig. 16 there is 

space in one bay for two complete systems. 

Each system consists of a line terminating 

shelf stack, a terminal repeater, 

a remote power feeding unit and a 

mains rectifier. The bay also contains a 

speaker circuit shelf that is common for 

the two systems. The shelves are in the 

M4 construction practice and the width 

of the bay is 600 mm. 

The line repeater is of the same mechanical 

design as in the other systems 

in the new generation. It consists of a 

small die-cast aluminium box with the 

dimensions 130x210x310 mm including 

the handle 4 . 

The line repeaters are installed in a 

waterproof cylindrical steel housing, 

which is buried in the ground or placed 

in a manhole. One of the types supplied 

by LM Ericsson holds three systems and 

this housing has a height of 750 mm and 

a diameter of 510 mm. When the line repeater 

is to be insulated from earth it is 

provided with an external case, fig. 17. 

This case is also used to absorb strong 

vibrations, which can occur when the 

cable is laid along motorways or railways. 

The line repeaters are easy to install if 

they are correctly equipped beforehand. 

This means that they are provided with 

— suitable gain 

— a crystal for the fault location 

— if necessary a line building-out network. 

Out in the field it is then only necessary 

Fig. 16 

60 MHz terminal bay 

The equipment for a fully equipped system is 

shown 

TR Terminal repeater 

LT Line termination 

PFU Remote power feeding unit 

SCS Speaker circuit shelf 

FLS Fault location shelf 

MR Mains rectifier 

opt Optional 

Fig. 17 

The cover for the line repeater, intended to 

Insulate it from earth and protect it from vibrations

Fig. 18 

The trial route, consisting of one line terminal, 

8 non-regulating and 2 regulating line repeaters 

and one cable equivalent 

Fig. 19 

Residual deviation curve before and after 

equalization 

pWOp/km 

Fig. 20 

Noise load curves for the line including the 

terminal 

Fig. 21 

The maximum variation of the residual deviation 

curve when the feeding current was varied by 

±10 mA and ±20 mA in relation to 290 mA 

to connect the repeaters to the relevant 

cable box in the steel housings. 

Trial route 

During the spring of 1977 a system trial 

was carried out on a route in the vicinity 

of Rome, where coaxial pairs 

were kindly provided by the Italian telecommunications 

administration ASST. 

System measurements were carried out 

in close collaboration by FATME and 

SIELTE, both members of the Ericsson 

Group, and LM Ericsson. The results 

were presented to ISPT, the State Institute 

for Post and Telecommunications, 

and to ASST, who also carried out measurements 

of their own. 

The trial route was equipped with a terminal 

bay and ten line repeaters, of 

which two were regulating. A system line 

with a length of 32 km was obtained by 

loop connection through a cable equivalent 

at the last line repeater, fig. 18. 

This length is sufficient in order to be 

able to check, by means of measurements, 

that the system functions satisfactorily 

and in accordance with the set 

design objectives. That this was so was 

also confirmed by the measurements 

that were carried out. It was easy to 

adjust the residual deviation curve to 

within ±1 dB with only the fixed equalizers, 

fig. 19. 

Noise measurements carried out on the 

whole system show good results. With 

a load of (-15dBmO/channel, the noise 

measured in the worst channel was 1.5 

pWOp/km, which is well below the value 

of 3 pWOp/km recommended by CCITT. 

The measured load curves also show a 

good margin against overload, see fig. 

20. 

The dependence of the level stability on 

variations in the feeding current was 

very small. This was established by measuring 

the residual deviation curve for 

various values of this current within the 

range 270 mA to 310 mA. Fig. 21 shows 

that only very small level deviations were 

found. 

The hum modulation was measured by 

superposing an alternating current on 

the constant direct current provided by 

the remote power feeding unit, and then 

changing the amplitude and frequency 

of the alternating current. High values 

of hum modulation attenuation were 

then obtained, fig. 22, which was partly 

expected in view of the feeding principle 

that had been chosen for the line 

repeaters, see fig. 5. 

The crystal filters for suppressing the 

regulating pilots provide high attenuation 

at the pilot frequency and a sharp 

cut-off, which is illustrated in fig. 23. 

Other measurements carried out were 

— attenuation of the near-end and farend 

crosstalk 

— supervision with fault location frequencies 

— simulation of a cable break 

— the dependence of the level stability 

on variations of the battery voltage. 

The results of these measurements are 

not given here, but all were satisfactory. 

The level stability as a function of the 

cable temperature was not checked, because 

the cable for the trial was buried 

at a considerable depth. In view of both 

the short route and the limited trial period 

no marked variations could be expected. 

Fig. 22 

Hum modulation attenuation measured for alternating 

currents of different amplitudes and frequencies 

superposed on the feeding current 

5 mA 

8 mA 

12mA

Technical data 

Electrical data 

Cable 

2.6/9.5 mm 

Section length with a mean cable temperature ot + 10°C 

1.55 km 

Transmission band 

3640-61160 kHz 

Number of telephony channels 10800 

Gain at 61160 kHz, variable in stepsofl dB 

28.5+3 dB 

Main regulating pilot 

61160 kHz 

Extra pilots 

22372 and 4287 kHz 

Pilot level 

-1OdBm0 

Regulation range at the respective pilot frequencies 

±3 dB 

Line building-out networks, variable in steps of 2 dB 

0-22 dB 

Fault location frequencies 

at intervals of 2 kHz in the band 

3640-4000 kHz 

level of each such frequency 

-30dBmO 

Harmonic ratio attenuation measured at 0 dBm: 

2nd order at 4 MHz 

>97dB 

3rd order at 60 MHz 

>108dB 

Noise, for the system loaded with -15 dBmO/channel 

100 dB 

Remote power feeding unit, PFU 

voltage 

20-1200 V 

constant direct current 

290 mA 

Mains rectifier, maximum output power 

440 W 

37 

The system fed from 

station battery mains rectifier 

Max. number of linerepeatersperPFUwitheveryfourthregulating 47 40 

Corresponding distance between power-feeding stations 147 km 126 km 

Mechanical data 

Bay 

Line repeater, incl. handle 

Housing for 3 systems 

600x225x2600 mm 

130x210x310 mm 

height 750 mm 

diameter 510 mm 

Summary 

The results of the different measurements 

carried out on the trial route 

show that the equipment meets all demands 

made on it, which was evidenced 

not least by the fact that CCITT recommendations 

were met with good margins. 

In this connection it is deserving 

of mention that the close cooperation 

between FATME and LM Ericsson has 

been of inestimable value both as regards 

the development of different 

parts of the system and the execution 

of measurements on the trial route, and 

also the production of line repeaters 

and other units included in the system. 

Fig. 23 

Attenuation of the main regulating pilot 61160 kHz 

in the receive direction of the line terminal 

References 

1. Ernbo, A.: Coaxial Cable for High 

Frequency Telecommunication 

Systems. Ericsson Rev. 5) (1974):3, 

pp 70-79. 

2. Englund, N.-G.: Coaxial Cable Systems: 

Operational Experience and 

Future Prospects. Ericsson Rev. 57 

(1974):1, pp. 13-20. 

3. Kallgren, O.: A New Generation of 

Line Systems for Small-Core and 

Normal Coaxial Cables. Ericsson 

Rev. 51 (1974):2, pp. 48-53. 

4. Breuer, H.-J.: Line Amplifier ZGC 

201 for 12 MHz Systems. Ericsson 

Rev. 57 (1974):2, pp. 54-60 

5. Manes, L. and Pausini, F.: A New 

Generation of Repeaters for Coaxial 

Cables. Not. teen. FATME No. 18, 

June 1976. 

6. Rydbeck, N.: Intermodulation Distortion 

for a 12 MHz Carrier Frequency 

System-Comparisons between 

Theory and Practice. Ericsson 

Tech. 32 (1976):2, pp.145-172.

Do the Media Understand 

Telecommunications 

Christopher Lorenz 

ERICSSON REVIEW plans to publish from time to time articles of a general interest 

in the field of communications. 

The second article in this new series has been written by CHRISTOPHER LORENZ 

of the Financial Times in London, who is one of the best respected telecommunications 

writers in the world press today. 

Mr. Lorenz discusses some of the problems of the "unknown" telecommunications 

industry and the lack of recognition for what this industry contributes. And 

suggests that one of the solutions might be education and information of mass 

media as a means of improving the general public's understanding of telecommunications. 

achieved high levels of telephone penetration, 

and are trying to improve the 

usage of their installed assets. 

Greater understanding from the public 

can also help the organisation in other 

ways, such as reducing the barrage of 

impatience and complaint when something 

goes wrong. This applies as much 

to the occasional breakdown as to the 

impact of changing levels of telephone 

network investment on employment in 

the factories which make telecommunications 

equipment. 

UDC 654.1: 

659.3 

Many a telecommunications professional 

has asked me over the years why his 

industry is so poorly understood by the 

general public, as compared with motor 

vehicles or shipbuilding-or even 

more "difficult" subjects such as 

nuclear power, genetic engineering or 

astro-physics. After all, he usually argues, 

telecommunications is of prime 

social and economic importance. 

A mass of factors supports his argument: 

efficient telephone and data networks 

are vital to the very life of a modern 

industrialised economy; operation 

of the systems and their manufacture 

together employ several hundred thousand 

people in each of many countries 

round the world; massive annual investment 

in the business is required (often 

running into several billions of dollars); 

taken together with associated activities 

like computing and electronic components, 

telecommunications will account 

for more than six per cent of several 

gross national products in Europe by 

the early 1980s; and on the question of 

technological innovation, the telecoms 

man will argue that current advances in 

both switching and transmission are as 

exciting as anything the motor industry 

or even nuclear power have to offer. 

This concern with the need for greater 

public understanding is not just a question 

of giving the telecoms professional 

the widespread recognition he deserves, 

alongside the designer of cars, or 

nuclear physicist. In almost every country, 

greater public awareness could promote 

demand for all sorts of telephone 

services —an important economic factor 

to countries which are now installing 

extensive networks for the first time, 

just as it is for those which have already 

If administrations and manufacturers 

are to get their message across, they 

will first have to persuade the media 

(both press and broadcasting) that they 

are in an interesting business. This will 

become harder in the next few years, as 

more and more equipment is compressed 

into obscure small boxes of integrated 

circuits controlled by computer 

tapes and discs. Even with traditional 

technology, it is not an easy task. 

From a journalistic point of view, the 

most obvious problem about the telephone 

is that, in many countries, people 

perceive it as "just part of the furniture". 

It has been around for so long that it 

has ceased to be an interesting object 

for many people —unless it breaks 

down, that is. 

In the United States, to some extent, 

the telephone has been given a new 

lease of life as an object of public interest 

by the advent of competition since 

1968 in parts of the telecommunications 

market. People's interest can hardly fail 

to be aroused when they are assaulted 

daily by the competing claims of various 

suppliers, and when their local shopping 

plaza contains at least one "Phone 

Mart" with a bewildering array of handsets 

in over a dozen colours. The competitive 

climate and the general public 

awareness it creates, stimulates the media 

to give telecommunications considerable 

"coverage". 

In Europe, by contrast, the media still 

generally turns its attention to telecommunications 

only when it is the subject 

of a major row, be this over the threatened 

admission or nationalisation of 

new suppliers (as in France and the 

United Kingdom in recent years), or the

39 

CHRISTOPHER LORENZ 

Financial Times 

London 

latest cut in Post Office orders —and 

therefore inevitable unemployment in 

the suppliers' factories. It is significant, 

for example, that many national newspapers 

in Europe have virtually ignored 

the major underlying reason for repeated 

rundowns in suppliers' labour 

forces: the shift from labour-intensive 

electro-mechanical switching to semielectronics. 

Instead, they have concentrated 

on the spate of downward revisions 

in Post Office equipment orders. 

This is the drama of which popular journalism 

is made, but it usually oversimplifies 

any situation to the extent of 

damaging distortion. It also misses the 

chance to produce a fascinating study 

of a major industry undergoing a complete 

change in character. 

There are other, more constructive 

ways in which the media could be encouraged 

to "cover" telecommunications". 

For the writer, telecommunications 

consumption of national budget 

resources can be made an interesting 

theme (whether you think it is too large 

or too small). So can the efficient management 

of the telecommunications 

administrations. PTTs are some of the 

largest employers in many countries, 

too, but how many people understand 

how they go about their complex business 

The social aspect of developments in 

telecoms provide another obvious 

wealth of interesting material, whether 

in developing countries (basic telephony 

as well as prestigious satellite projects), 

or in the industrialised world. Here, one 

should not need to repeat the well-worn 

futuristic cliches about "working from 

home" or "the wired city" in order to 

provoke interest. Special services for 

handicapped people, or telephone audio 

conferencing (including its energysaving 

aspects) are down-to-earth 

examples. 

To the engineer, these themes may 

seem too lightweight, especially if his 

complaint is addressed more towards 

the lack of public understanding about 

the technological progress in which he 

is so closely involved, and which he may 

soon want to market in a new service. 

Of all the current examples, only videoconferencing 

has attracted widespread 

popular coverage by the media in a 

number of countries (this includes the 

view- or picture-phone). Electronic 

switching, waveguides and even optical 

fibres have received little more than the 

occasional mention in most general 

newspaper (my own is an exception). 

It is often impossible to write about an 

economic or organisational aspect of 

telecommunications without getting 

deeply into technological issues. Unless 

the journalist explains the technical 

principles and carrying capacity of optical 

fibres, for instance, he cannot hope 

to convey how important they may be in 

cutting transmission costs, providing 

greater bandwith, and therefore offering 

subscribers a whole new range of services 

at reasonable prices. But this need 

to use technology as a "lever" can become 

a barrier to writing about telecommunications 

at all. 

This is the crux of the problem. Many 

people—including some newspaper 

editors-are quite simply scared off by 

technology, some by the word itself, 

others by its complex (and sometimes 

disturbing) implications. Many editors 

also have an unfortunate habit of underrating 

the intelligence of their public. 

This compounds the problem facing a 

company or organisation which is trying 

to popularise telecommunications. 

A recent television programme about 

telephony is an ideal example here. 

Much of it consisted of pictures of workmen 

erecting telephone poles in beautiful 

countryside, though the programme 

had nothing directly, to do with the environmental 

effects of technology. Quite 

rightly, many telecommunications professionals 

were extremely disappointed 

by the film. 

Its shortcomings were partly explained 

by the fact that shots of people at work 

are easier and cheaper to take than 

those of technological equipment or 

processes. But the programme makers 

also assumed that viewers prefer watching 

objects they can immediately indentify, 

rather than those which are unfamiliar. 

Telephone exchange equipment 

is an obvious problem here. 

The film-makers also felt that switching 

equipment could not be made visually 

interesting unless large parts of it were

40 

seen to move. So they were forced to go 

along to one of the oldest Strowger exchanges 

they could find. Even then, 

they had to persuade the exchange's 

entire staff to dial each other for minutes 

on end, in order to set enough of 

the switches moving and clattering! 

Another possible problem was the current 

fashion in television for "allowing 

the pictures to tell the story", rather 

than gathering experts in a studio or on 

location to discuss it. "Talking heads" 

(as such expert discussions are called 

in the trade) are all but banned by the 

editors of some TV programmes. This 

attitude militates strongly against the 

coverage of complex industrial subjects, 

and in favour of riots, natural disasters 

and the like. 

Even where such fashions carry little 

weight, there are other problems. A different 

TV station took the ambitious 

step of making a general-interest programme 

about the impact of microprocessors 

on a wide range of industry. 

The staff immediately faced the problem 

of filming something as small and static 

as a tiny chip of silicon without incurring 

the high cost of microscopic pictures 

and of effectively covering at the 

same time the changes in strategy being 

forced in industry by the new technology. 

For some viewers, the pictures 

appearing on the screen of microcircuit 

manufacture and computer assembly 

were irrelevant to the accompanying 

discussion of the industrial strategy 

issues; the pictures were described by 

some of the staff themselves as "wallpaper" 

against which to set the words 

of commentary. The industrial issues, in 

turn, were difficult to explain without a 

mass of charts and "talking heads". 

These two television programmes were 

unusual in that they tried to make a serious 

examination of the issues surrounding 

generally unfamiliar technologies. 

The second was far more successful 

than the first, even though 

microprocessors are more difficult to 

handle than telecommunications in visual 

terms. There were a few distortions 

of detailed fact but at least the electronics 

engineers could be thankful that 

they were minor. 

One only needs to consider nuclear 

power to get a very different storymore 

than any other form of high technology, 

it is always "news" for the TV 

and newspapers. No nuclear physicist 

can claim that his work is ignored by the 

media. Instead, he will complain about 

distortion and about "environment correspondents" 

whose business seems 

often to consist solely of spreading 

gloom and doom. 

Telecommunications can hardly be presented 

as physically dangerous, so it 

should always be spared such an extreme 

type of bad press. All the same 

considerable ingenuity will be required 

from the industry itself, as well as the 

media, if the issues are to be presented 

accurately, but in a way the public can 

understand. 

There is, I think, a case for both telecommunications 

administrations and 

manufacturers to devote close attention 

to the education and information of the 

media. Telecommunications will never 

be well understood by the public unless 

the media understand it first.

The Ericsson Group 

With associated companies and representatives 

EUROPE 

SWEDEN 

Stockholm 

1. Telefonaktiebolaget LM Ericsson 

2. LM Ericsson Telemateriel AB 

1, ABRifa 

1. Sieverts Kabelverk AB 

1. Svenska Radio AB 

5. ELLEMTELUtvecklings AB 

1. AB Transvertex 

4. Svenska Elgrossist AB SELGA 

1. Kabmatik AB 

4. Holm & Encsons Elektnska AB 

4. Mellansvenska Elektnska AB 

4. SELGA Mellansvenge AB 

Allngsfis 

3. Kabeldon AB 

Gavle 

2. Vanadis Entreprenad AB 

Gothenburg 

4. SELGA Vastsvenge AB 

Kungsbacka 

3. Bota Kabel AB 

Malmo 

3. Bjurhagens Fabnkers AB 

4. SELGA SydsvengeAB 

Norrkoping 

3. AB Norrkopings Kabelfabrik 

4. SELGA Ostsvenge AB 

Nykoplng 

1. Thorsman & Co AB 

Sundsvall 

4. SELGA Norrland AB 

Vaxjo 

1. Widells Metallprodukter AB 

EUROPE (excluding 

Sweden) 

BELGIUM 

Brussels 

2. Ericsson Belgium sa/nv 

DENMARK 

Copenhagen 

2. LM Ericsson A/S 

1. Dansk Signal Industri A/S 

3. GNT AUTOMATIC A/S 

1. I. Bager& Co A/S 

2. LM Ericsson Radio ApS 

Tastrup 

2. Thorsman & Co ApS 

FINLAND 

Helsinki 

2. Oy Thorsman & Co Ab 

Jorvas 

1. Oy LM Ericsson Ab 

FRANCE 

Colombes 

3. Societe Francaise des 

Telephones Ericsson 

Boulogne sur Mer 

1. RIFA S A 

Marseille 

4. Etablissements Ferrer-Auran S A 

IRELAND 

Athlon e 

1. LM Ericsson Ltd 

Drogheda 

2. Thorsman Ireland Ltd 

ITALY 

Rome 

1. FATME Soc. per Az 

1. Scarfini Soc per Az 

5. SETEMER Soc. per Az 

2. SIELTE Soc. per Az. 

The NETHERLANDS 

Rijen 

1. Ericsson Telefoonmaatschappj] B.v. 

NORWAY 

Nesbru 

3. A/S Elektrisk Bureau 

3 United Marine Electronics A/S 

Oslo 

2. SRA Radio A/S 

2. Thorsman & Co 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. Industnas de Telecomunicaci6n S A 

(Intelsa) 

1. LM Ericsson S A 

SWITZERLAND 

Zurich 

2. Ericsson AG 

UNITED KINGDOM 

Chorley 

2. Thorsman & Co (UK) Ltd 

Horsham 

4. Thorn-Ericsson Telecommunications 

{Sales) Ltd 


(Rentals) Ltd 

5. Swedish Ericsson Company Ltd 


(Mfg) Ltd 

6 Thorn-Ericsson Telecommunications 

Ltd 

London 

4. United Marine Leasing Ltd 

4. United Marine Electronics (UK) Ltd 

WEST GERMANY 

Frankfurt-am-Main 

2. Rifa GmbH 

Hamburg 

4. UME Marine Nachnchtentechnik, GmbH 

Hanover 

2. Ericsson Centrum GmbH 

Ludenscheid 

2. Thorsman & Co GmbH 

Representatives in: 

Austria. Greece, Iceland, Luxembourg, 

Yugoslavia. 

LATIN AMERICA 

ARGENTINA 

Buenos Aires 

1. Cia Ericsson S A.C.I 

1. Industnas Electncas de Quilmes S A 

5. Cia Argentina de Telefonos S A. 

5. Cia Entrernana de Telefonos S.A 

BOLIVIA 

La Paz 


BRAZIL 

Sao Paulo 

1. Ericsson do Brasil Comercio e 

Industna S.A 

4. Sielte S.A. Instalacdes Eletncas e 

Telefonicas 

4. TELEPLAN, Projetos e Planejamentos 

de Telecommumcacoes 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 

Cali 

1. Fabricas Colombianas de Materiales 

Electncos Facomec S.A. 

COSTA RICA 

San Jose 


ECUADOR 

Quito 

2. Telefonos Ericsson C A 

GUATEMALA 

Guatemala City 


Port-au-Prince 

7. LM Ericsson 

MEXICO 

Mexico OF 

1. Teleindustna Ericsson. S A 

1. Latmoamencana de Cables S A. 

deC V 

2. Telefonos Ericsson S A 

2. Telemontaie, S A de C V 

PANAMA 

Panama City 

2. Telequipos S A 


PERU 

Lima 

2. Cia 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, 

French Guiana, Guadeloupe, Guatemala, 

Guyana, Honduras, Martinique, Netherlands 

Antilles, Nicaragua. Panama, Paraguay. El 

Salvador, Surinam. Trinidad, Tobago. 

AFRICA 

ALGERIA 

Algiers 


EGYPT 

Cairo 


LIBYA 

Tripoli 


TUNISIA 

Tunis 


ZAMBIA 

Lusaka 

2. Ericsson (Zambia) Limited 


Installation Branch 


Angola, Benin, Botswana. Cameroon, Central 

African Empire, Chad, Congo, Egypt. 

Ethiopia, Gabon. Ivory Coast, Kenya, Liberia. 

Libya, Madagaskar, Malawi, Mali, Malta. 

Mauretama, Morocco, Mozambique. Namibia. 

Niger, Nigeria. Republic of South Africa. 

Reunion, Senegal, Sudan, Tanzania, Togo. 

Tunisia, Uganda. Upper Volta, Zaire. 

ASIA 

Calcutta 

2. Ericsson India Limited 

INDONESIA 

Jakarta 

2. Ericsson Telephone Sales 

Corporation AB 

Baghdad 


IRAN 

Teheran 

2. Ericsson Telephone Sales 

Corporation AB 

3. Simco Ericsson Ltd. 

4. Aktiebolaget Enfon 

KUWAIT 

Kuwait 


LEBANON 

Beirouth 

2. Societe Libanaise des Telephones 

Ericsson 

MALAYSIA 

Shah Alam 

1. Ericsson Telecommunications 

Sdn Bhd 

OMAN 

Muscat 


SAUDI ARABIA 

Riyadh 


Bangkok 

2. Ericsson Telephone Corporation 

Far East AB 

Ankara 

2. Ericsson Turk Ticaret Ltd Sirketi 


Bahrein, Bangladesh. Burma. Cyprus. Hong 

Kong, Indonesia. Iran, Iraq, Jordan, Kuwait, 

Lebanon, Macao, Nepal, Oman, Pakistan, 

Philhppines, Qatar, Saudiarabia, Singapore, 

Sri Lanka, Syria, United Arab Emirates. 

UNITED STATES and 

CANADA 

UNITED STATES 

Woodbury NY. 

2. LM Ericsson Telecommunications Inc 

New York, NY. 

5. The Ericsson Corporation 

CANADA 

Montreal 

2. LM Ericsson Ltmitee/Limited 

AUSTRALIA and 

OCEANIA 

Melbourne 

1. LM Ericsson Pty Ltd 

1. Rifa Pty Ltd. 

5. Teleric Pty Ltd 

5. LM Ericsson Finance Pty, Ltd 

Sydney 

3. Conqueror Cables Ltd 


New Caledonia, New Zealand. Tahiti 

1. Sales company with manufacturing 

2. Sales and installation company 

3. Associated sales company with manufacturing 

4. Associated company with sales and 

installation 

5. Other company 

6. Other associated company 

7. Technical office

TELEFONAKTIEBOLAGET LM ERICSSON 

ISSN 0014-0171 Printed in Sweden L/ungforetagen, Orebro 1978

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