Table Of ContentA MANAGER'S GUIDE TO
TELECOMMUNICATIONS
Martin Gandoff
Heinemann: London
William Heinemann Ltd
10 Upper Grosvenor Street, London W1X 9PA
LONDON MELBOURNE
JOHANNESBURG AUCKLAND
First published 1987
©Martin Gandoff 1987
British Library Cataloguing in Publication Data
Gandoff, Martin
The manager's guide to telecommunications.
1.Office practice - Great Britain - Automation
I. Title
651 HF5548.2
ISBN 0 434 91068 6
Typeset by Express Typesetters Limited, Farnham
Printed by R. J. Acford, Chichester, West Sussex
List of illustrations
Chapter 1 Communication and computers 2.16 Modular Technology Minimodem 3005
acoustic coupler 44
1.1 The ASR33 teletype 14 2.17 BT Merlin DM4962X modem 44
1.2 ASCII characters 17 2.18 Miracle Technology WS2000 modem 46
1.3 A mouse in use 18 2.19 Modular Technology Microdriver
1.4 A daisywheel printer 19 line driver 47
1.5 Magnetic diskettes 19 2.20 An example of multiplexing 48
1.6 Communications services 21 2.21 Mercury antenna, 13-metre, at
1.7 Main software applications 22 East End Wharf 51
1.8 A typical menu 23 2.22 Jointing optical fibre 52
1.9 A spreadsheet 'top line' menu 23 2.23 The character Έ' in the
1.10 A GEM screen 24 code EBCDIC 54
1.11 Homebanking 26 2.24 The character 'E' distorted to give 'N' 54
2.25 The character Έ' distorted to give 'D' 54
2.26 ASCII characters with parity
Chapter 2 Transmission technology and bit attached 54
techniques 2.27 Parity checking in two directions 54
2.1 Typical screen dialogue 33
2.2 Serial and parallel transmission 35 Chapter 3 Networks and exchanges
2.3 A sine wave 36
2.4 A typical speech waveform 36 3.1 The development of switch
2.5 Digital data 37 technology 61
2.6 Digital data distorted during 3.2 Standard PABX installation layout 63
transmission 37 3.3 Northern Telecom DMS250 63
2.7 Part of the character Τ in ASCII 38 3.4 Thorn-Ericsson AXE10 exchange 64
2.8 The 'Carrier' wave 39 3.5 Access to the AXE10 64
2.9 Original bit pattern 39 3.6 BT Monarch IT440 65
2.10 Carrier amplitude-modulated by the 3.7 BT Viceroy, Kinsman and
signal 39 TX14 featurephone 66
2.11 Carrier frequency-modulated by the 3.8 A Plessey ISDX installed in an office 66
signal 40 3.9 The Plessey ISDT digital services
2.12 Carrier phase-modulated by the telephone/entry terminal 67
signal 40 3.10 Alternative views of packet
2.13 Amplitude modulation 41 transmission 69
2.14 Multilevel states for transmission 41 3.11 Standard 'packet' format 70
2.15 Multiplexing onto a broadband 3.12 HDLC 'packet' format 71
channel 43 3.13 PSS access routes 71
7
List of illustrations
Chapter 4 Telephone and telephone-linked 4.43 The Talkback'network' 103
facilities
4.1 Setting up a directory entry including Chapter 5 Text and document transmission
short code 78
4.2 A computer services directory entry 78 5.1 The Hasler Protelex menu 108
4.3 BT Monarch IT440 80 5.2 The 3M Whisper telex 110
4.4 BT Merlin TX72 featurephone 81 5.3 The Olivetti TE530 110
4.5 Merlin Viceroy and Kinsman consoles 5.4 BT Merlin Sable telex terminal 111
and the TX14 featurephone 81 5.5 BT Merlin Cheetah Teleprinter 111
4.6 A range of Thorn-Ericson 5.6 BT Merlin Puma telex terminal 111
featurephones that complement the 5.7 Transtel Com Writer III with matrix
MD110 switch 82 printer and keyboard with autodial
4.7 Ansafone E616 featurephone 83 keys 111
4.8 Philips KBX6 telephone system 83 5.8 Transtel ComMaster telex terminal 112
4.9 Philips KT4 featurephone 84 5.9 Close-up of English/Arabic
4.10 Merlin Octara 32 digital key system translation 112
with 3 featurephones 84 5.10 Telex menu from the DCE
4.11 Call listing 86 Telexbox-3 112
4.12 Selective reports 86 5.11 A telex in preparation 113
4.13 Usage histograms 87 5.12 An outgoing telex queue for
4.14 Department totals 87 examination 113
4.15 Specific reports 87 5.13 The Hasler telex with an IBM PC 113
4.16 Ansafone Telcost 64 88 5.14 A DCE Telexbox-3 with an
4.17 Merlin CM8000 call analysis screen 88 ICL OPD 113
4.18 TONTOinuse 89 5.15 One-to-One in use from a mobile
4.19 A Microdrive cartridge 90 terminal using a cellular radio link 115
4.20 TONTO top-level menu 91 5.16 One-to-One electronic mail 115
4.21 A Priority Directory display 91 5.17 Initial Gold dialogue and message
4.22 The telephone keypad 91 display 117
4.23 The TONTO Voice Response library 91 5.18 MerlinTex adaptor with MT4000
4.24 QUILL in use 92 microcomputer 118
4.25 Display of an ARCHIVEd record 92 5.19 The EMT 9715 fax transceiver
4.26 ABACUS in use 92 from 3M 122
4.27 EASEL displays 92 5.20 Touch panel from the 3M EMT 9146 122
4.28 The Northern Telecom Displayphone 93 5.21 MerlinFax transceiver 123
4.29 BT Merlin Qwertyphone 93 5.22 The Plessey PDF-5 124
4.30 The cellular/PSTN network interface 94 5.23 Xerox 7010 125
4.31 Citifone production at Racal Seaton 5.24 Canon FAX-520 125
in Devon 95 5.25 Operation panel of the Canon
4.32 The Racal Citifone mobile cellular FAX-720 126
telephone 96
4.33 The Racal CT transportable Vodafone 96 Chapter 6 On-line database access and viewdata
4.34 The Racal VM1 mobile Vodafone 97
4.35 The Racal VM1 handset 97 6.1 A conceptual ordering screen 130
4.36 BT Opal fully portable cellphone 98 6.2 An Effem screen, daily report -
4.37 BT Jade transportable 98 summary 130
4.38 BT Amethyst for in-car use 99 6.3 Menu explanation screen from Effem 131
4.39 A Racal cellular data terminal 100 6.4 Prestel telex facilities 132
4.40 Autophone data entry Tonepad 101 6.5 Prestel teleshopping 132
4.41 Autophone backup demonstration 102 6.6 Two different keyboards, two
4.42 The Talkback unit with two integral different ELF displays (courtesy
magnetic tape drives 103 Easydata Ltd) 134
8
List of illustrations
6.7 A statement from Bank of Scotland 6.26 Effem electronic mail 145
'Homebanking' 135 6.27 Philips HCS 110 executive viewdata
6.8 Access to viewdata (courtesy Effem) 135 terminal 146
6.9 Serial vs parallel transmission of
attributes 136 Chapter 7 Local Area Networks (LANs)
6.10 Shopping with Harrods via Prestel 136
6.11 Alphamosaic build-up of the 7.1 Conceptual LAN components 152
character 'G' 136 7.2 Slough College Harris star network
6.12 Using graphics for effect 1: a structure 155
Micronet adventure 137 7.3 A conceptual tree structure 156
6.13 Using graphics for effect 2: Mars 7.4 Slough College Econet structure 157
European centres 137 7.5 A conceptual ring structure 157
6.14 An ICV financial menu 138 7.6 Security linking of alternate devices 157
6.15 A financial display from ICV on an 7.7 An LAN loop 158
Easydata ELF 138 7.8 Ethernet packet format 160
6.16 Welcome from the London Borough 7.9 LAN potential user/usage matrix 162
of Hackney 139
6.17 The HOBS 'welcome' screen 139
6.18 HOBS inter-account transfers 140 Appendix 1 Mercury
6.19 HOBS statement analysis 140
6.20 Thomas Cook viewdata structure Al.l Mercury distribution node 165
(courtesy Microscope Ltd) 141 A1.2 Close-up of a microwave antenna at
6.21 A text display of dollar quotations Charing Cross Hospital 166
from Datastream 142 A1.3 Installing optical-fibre cable in the
6.22 London gold and silver prices from City of London 167
Datastream 143
6.23 Gold/platinum ratio 143 Appendix 5 The ISO 7-layer model
6.24 Data from the US 'meat exchange' 143
6.25 Log-on for PVS-NET 144 A5.1 The OSI 7-layer model 177
9
Preface
While researching material for this book, I In order to keep the book to a manageable size I
realised very quickly that I had set myself an have had to omit several areas; this will probably
extraordinarily difficult task. It is never easy to do annoy some readers. In particular, there is no
a book covering a dynamic area, but with coverage of answering machines, paging
telecommunications (transfer of information over equipment and video.
a distance) both for voice and data, the last couple
of years have seen the technology expand in leaps For the subjects of Chapters 4-6,1 have discussed
and bounds and with it, the applications or the relevant theory, broadly reviewed the range
modifications to existing applications. of facilities and then given examples of hardware
and software. You will note that I have made
In my view, any attempt to produce a book that almost no recommendations as to specific products
is not out of date before it is read can only be - I never intended to produce a buyer's guide.
successful if it sets out to educate managers in the
basic principles behind the various techniques and I hope that by the time you have read the book,
encourages them to look more deeply into what you will be able to answer at least partially,
is available. questions such as:
In accord with well defined management practice, • This sounds interesting, what is it?
good managers need enough background in a • What can I do to find out more about it?
subject to be able to brief subordinates so that they • What can it do?
know what to do or what to look for, and then to • How does it work?
be able to appreciate what they return with so that • How will it help me?
the right decisions can be made. So, apologies for • How do I find out which one to select?
the high 'teaching' content.
At the back, you will find a fairly long glossary of
I have been very careful not to distinguish between terms. I make no apology for this. There are so
telecommunications (telecomms), which tradi- many buzzwords and terms in use, many of which
tionally has meant voice communication, and data are similar, that a quick-reference dictionary like
communications (datacomms). As separate areas, this one would have helped me considerably.
they often come under the control of a
telecommunications manager on the one hand and I would like to express profound gratitude to
a data processing manager on the other. I believe everyone that gave me help in the form of product
that the distinction is now really rather pointless, information, customer education material,
since, as will be discussed, the two types of photographs and a lot of their time: in particular,
communication often use the same technology, the Northern, Mercury, Easy data, Effem and John
same networks and often even the same wire. The Smart of Manners, Borkett and Partners (who
buzzword for this meeting of voice and data is handle some of BT's PR). Especial mention for
'convergence'. Gloria for so much moral support during the
11
Preface
What does the manager want to know? What What are System X and digital data transfer?
does he want to be told? Can I avoid teaching
him? No I can't - he needs to know much more What is ISDN and when is it coming?
and, hopefully, I know more than him.
What is teletext? We know it is an international
The subject is incredibly wide and certain con- agreement and will replace electronic mail, but
cepts/techniques will bubble to the surface is there a network in existence; how do we get
almost immediately. into it?
BT Bless them! They can't or won't tell you all There seem to be very recent developments
about their services in a structured way. It seems whereby telex, slow data, teletext, fax, etc., will
that there is a very wide range of services based be mutually interfaceable. How? When?
initially on different networks for different ap-
plications. We must tell people about the main LANs. What are they? What benefits? What is
functions/workings of PSTN and PSS. What is available? What kind do I want? How do I work
the set-up behind the telephone handset - out what hardware/costs, etc. Can I get into other
PABX, lines etc. How is a call routed through people's?
the network? How does the system sort out STD
codes? Viewdata/videotex seem interesting. What is the
difference? Can I get into other people's? How?
Where does computing come in? Can I do some Could I set up my own?
data processing with my terminal? Can I use it
for telex, teletext, etc.? Can I use my PC and its What are all these protocols and standards,
word processor to set up telexes, electronic mail, especially V.24, X.25, OSI.
etc.?
Can I have a list of buzzwords and brief ex-
How can you make better use of your telephones planations?
- through BT and other suppliers?
How have things gone over the last 5-10 years
What are the essential differences between and where are they going because, now I am
Telex, voice, slow data and the various fast data interested, I want to plan for the future?
services?
Will cellular telephone provide a reliable mobile
data terminal?
doldrum period when 'nobody would tell me by the presentation and content of much of the
anything', Nigel Stewart for help with the proof- trade literature. Companies like DEC, Rank-
checking, and my friend and colleague Osie Xerox and Plessey produce beautiful and very
Pereira (Head of Science and Technology at readable material.
Slough College), whose patience in explaining
some of the trickier concepts at idiot level for me Finally, as an overview of this book, you might be
cannot be valued. interested to see the notes I made in the very first
hour's work I did for the book. These are
Without all this help, cooperation and guidance, reproduced above.
I could never have sorted the book out.
Incidentally, you will be very agreeably surprised M. Gandoff
12
Chapter One
Communication and computers
The development of voice and a coded form. Then these would be taken into the
data transmission computer room and fed into the input device
(card- or paper-tape reader) under the control of
Let us start with a point raised in the Preface, i.e. the relevant program. Only then could files be
the difference between telecommunications and updated and printed reports produced. By the
data communications. When long-distance early 1960s, both manufacturers and users of
communication first started in the 19th Century, computers were becoming painfully aware that
the name used was telegraph, 'writing at a distance' there had to be a better way to gain access to
(from the Greek words). Then came the word computer power than this, the only route available
telephone, 'speaking at a distance'.Since then we at the time.
have seen telex, teletext, télétex and so on.
This not very 'user-friendly' performance was
Voice and telex transmission technology have given the name batch processing, mainly to indi-
developed since then and were in very widespread cate that data originated in a batch, as far as the
use by the end of the Second World War. At this computer was concerned. The computer processes
time, the computer started to appear and was well (programs) required would be carried out so that
established by the late 1950s. the batch retained its identity right through the
data processing cycle. It was becoming increas-
No apology is made for the fact that much of this ingly obvious that a method was needed that would
chapter is concerned with computing and data provide computer processing (access to the
processing as a lead-in to data communications, computer's processing power and data storage
rather than with telecommunications. Almost all capacity) at the point of service, i.e. where data or
data transmission is controlled by computers these the request for computer processing originates
days and you need to have a feel for data rather than at a central or host computer. For
processing in order to appreciate what is example, in a warehouse, it would be nice to be
happening and how the various services and able to enter stock deliveries and at the same time
facilities fit together and can be accessed. have the computer record them so that other users
could request up-to-date stock reports. Similarly,
Before data communications became possible, an engineer on a customer's premises might need
computer processing had to be from a main to carry out a complex stress calculation using his
computer within the building where processing own company's computer and the same might
was required (often referred to as in-house apply to a marketing man wanting to do a fancy
processing).This meant that users, those that sales forecast or delivery date calculation.
needed their data processed and results generated,
had to take their source documents (invoices, A manager could receive a lot of decision support
time-sheets, production schedules etc.) to a data from a computer if he had access to a range of
preparation bureau who would produce punched databases containing financial and business in-
cards or paper tape containing the 'source data' in formation, to management science and statistical
13
Communication and computers
software. Obviously, only large companies with communication medium, the telex lines being a
adequate resources and know-how could provide little too slow.
this kind of facility in-house.
To save connect-time, i.e. to avoid having to enter
Remember that the micro with any respectable the wording of the telex while connected, the
software has only been around since about 1980 teletype was fitted with a paper tape read/punch
and in the early to mid-60s, computers were either and as keys were pressed, as well as being trans-
fairly small and unsophisticated or large and ferred to the printer paper-roll, they were copied
expensive. So until recently, there was always the onto the paper tape in ASCII code (coming up
problem that data processing could only be carried later). Once the text had been completed, a telex
out in batch mode. connection could be made and the actual message
entered from the tape through the tape reader. (In
Public voice telephony on the other hand really fact, paper tape has been employed in this way
presented no such problem apart from the general right up to today, although its use is dying out since
difficulties of trying to reduce mis-routings and 'intelligent' telex machines are often equipped
background noise and generally increase the with magnetic disk or some other method of
efficiency of the telex and public telephone storing messages before transmission, such as
systems with the increasing level of traffic in- extra magnetic memory.) The ASR33 remained in
tensity. use as an unintelligent computer terminal (no data
processing power of its own) for quite a long time,
Obviously, both the military and business uses of the user preparing data and programs on the
computers were being rapidly recognised and off-line paper tape punch and then feeding them
developed and it was only a matter of time before in once connection had been made to the com-
electronics and telecommunications equipment puter.
suppliers started to make extensive use of solid-
state circuitry leading up to the now very So, once industry had cracked the problem of
widespread application of microprocessors. converting computer-acceptable data, such as
Similarly, computer manufacturers were able to from the teletype, into a form that could be
produce the software that could drive data and transmitted through the telephone system, and
interconnect the central computer and other com- then getting it back into an acceptable form for the
puters or terminal devices such as computer itself, on-line or remote computer
VDU/key boards. processing became possible.
It is not really surprising that things have only just Of course, the software needed to be rethought,
started in a very big way. There are quite a few both to be able to handle processing for a number
problems associated with communications of all of remote users (not much point if just one batch
kinds, related to the different switchboards and
exchanges in use, the different terminals used, the
different computers that back up much of the
processing and the fact that we are connecting
public and private services, in the UK and abroad.
(In recent years, there has been implemented an
international network for data transmission which
links many different countries.)
For telex, the ASR33 teletype, first produced by
Bell in the USA, had been in use for quite a while.
This was basically a keyboard/slow printer that
could be linked into the telex system both for
sending and receiving and it seemed obvious that
the teletype provided a means of connecting to a
computer, at a distance from it. Equally obvious
was the use of the telephone system as the Figure 1.1 The ASR33 teletype
14
Communication and computers
user at a time can be serviced) and to sort out the complete networks that link in with the BT
communications problems, such as who gets network. Yet other companies supply VANs
service next, error detection and recovery, (Value Added Networks) in which existing BT and
collecting statistics of facility usage (for control Mercury networks are used and extra facilities are
and future planning), etc. provided, e.g. electronic mail and home banking.
In the mean time, the Post Office had not been idle Networks that cover an area larger than a single
and could see the potential for data transmission building, whether for public or private use, are
as well as the large increase in the use of voice given the name Wide Area Network (WAN).
telephone and was already planning for what was
to become the completely new, British Telecom On a completely different level, for several years
System X, the computer-controlled public now, many companies have been putting together
switched voice and data networks. The new and supplying their version of a Local Area
technology was also implemented for the eventual Network (LAN). The main difference between a
introduction of ISDN, the Integrated Services WAN and an LAN is that the WAN can cover an
Digital Network, which is intended once the full area from many metres to the whole world, while
network has been implemented, to be used for the LANs are usually aimed at rooms, floors or
transmission of all kinds of data. possibly whole buildings. In addition, the LAN is
usually geared to a smallish number of users, with
Before going on to review computer applications data transmission not relying on telephony
we must say a little more on the concept of a techniques. An LAN will involve between, say,
'network'.The term is probably the most widely four and dozens of users, while a WAN could link
used word in communications and basically means thousands of distant users and may be based on
a set-up of telephones and/or terminals, with a speech or data transmission techniques.
connection path or transmission medium and a
mechanism for controlling the interconnection or
switching of calls. That supplied by British A review of data processing
Telecom for speech and low-speed data is called
the PSTN (Public Switched Telephone Network). In order to appreciate the facilities available to the
The more recent extension to this is the Packet remote computer user, it is necessary to do a
Switched Network called Switchstream. Telex is capsule review of what data processing is about.
handled by a different network although there has So let us start with the machinery and equipment.
been increasing interest and usage of télétex, a
standard approach to electronic mail which may
eventually replace telex. Hardware
Since 1981, after the Telecommunications Act Computers themselves consist of three basic
made it possible for companies other than British components: memory, the processor and
Telecom to offer public network services, Mercury peripherals.
Communications Ltd was formed by Cable &
Wireless (a British company that supplies a wide Memory The electronic memory (these days
range of telecommunications equipment and usually called RAM - random access memory), is
services overseas), British Petroleum and Barclays the electronic part of the computer into which data
Merchant Bank. It is now wholly owned by Cable must be temporarily loaded so that it can be
& Wireless. processed and into which programs must be loaded
so that they can run. This is often backed up with
Mercury are now able to supply a network which a slightly different type of memory with the
complements and can provide an alternative to generic name ROM (read only memory) in which
that of BT. A number of companies, such as programs can be permanently stored for im-
Plessey and GEC, provide complete networks for mediate use. The difference between RAM and
private use, such as might be the case on a factory ROM will come out when we talk about software.
site or an even wider area using microwave or laser
equipment to transmit data between points or The basic construction of any kind of memory is
15
