Understanding Data Communications.pdf

Understanding Data Communications: From Fundamentals to Networking.

Third Edition Gilbert Held

Print ISBN 0-471-627453 Online ISBN 0-470-84148-6

UNDERSTANDING

DATA COMMUNICATIONS

Understanding Data Communications: From Fundamentals to Networking.

Third Edition Gilbert Held

Print ISBN 0-471-627453 Online ISBN 0-470-84148-6

UNDERSTANDING

DATA COMMUNICATIONS

FromFundamentalstoNetworking

ThirdEdition

GilbertHeld

4 -Degree Consulting

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Library of Congress Cataloging-in-Publication Data

Held, Gilbert, 1943-

Understanding data communications: from fundamentals to networking / Gilbert Held.

p. cm.

ISBN 0-471-62745-3 (alk. paper)

1. Data transmission systems. 2. Computer networks. I. Title

TK5105 .H429 1997

004.6 — dc20

00-032094

British Library Cataloguing in Publication Data

A catalogue record for this book is available from the British Library

ISBN 0 471627453

Typeset in 9 2 /11 2 pt Bookman by Aarontype Ltd, Easton, Bristol

Printed and bound in Great Britain by Antony Rowe Ltd, Chippenham, Wiltshire.

This book is printed on acid-free paper responsibly manufactured from sustainable forestry,

in which at least two trees are planted for each one used for paper production.

Understanding Data Communications: From Fundamentals to Networking.

Third Edition Gilbert Held

Print ISBN 0-471-627453 Online ISBN 0-470-84148-6

CONTENTS

Preface xix

Acknowledgements xxi

1 Communications in a Modern Society 1

1.1 Applications 1

1.1.1 Data collection 2

1.1.2 Transaction processing 3

1.1.3 Conversational time sharing 5

1.1.4 Remote job entry 7

1.1.5 Message switching 7

1.1.6 Value-added carriers and electronic mail 8

1.1.7 O(ce automation 12

1.1.8 Electronic commerce 14

1.1.9 Satellite transmission 16

1.2 Constraints 16

1.2.1 Throughput 17

1.2.2 Response time 18

1.2.3 Bandwidth 18

1.2.4 Economics 19

1.3 Emerging Trends 19

1.4 ReviewQuestions 20

2 Basic Telegraph and Telephone Operations 23

2.1 Evolution of Communications 23

2.2 Telegraphy 24

2.2.1 Operation 24

2.2.2 Morse code 26

2.2.3 Morse code limitations 27

2.2.4 Start–stop signaling and the Baudot code 28

2.2.5 Bits and codes 29

2.3 Telephony 32

2.3.1 Principle of operation 32

2.3.2 Sound wave conversion 34

2.3.3 The basic telephone connection 36

2.3.4 Switchboards and central o ( ces 37

2.3.5 Numbering plans 39

2.3.6 Geographic calling areas and network routing 40

2.3.7 The world numbering plan 43

2.4 ReviewQuestions 43

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