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Thông tin thiết kế mạch P8

THE TELEPHONE NETWORK The early history of the telephone system has been outlined in Chapter 1. The growth of the telephone system has been truly phenomenal and forecasts show a continuing growth as new services such as data transfer, facsimile and mobile telephone are added. The telephone differs from the broadcasting system in two basic ways: (1) In broadcasting, a few people who, in theory, have information send it out to the many who are presumed to want the information; it is one-way traffic | Telecommunication Circuit Design Second Edition. Patrick D. van der Puije Copyright 2002 John Wiley Sons Inc. ISBNs 0-471-41542-1 Hardback 0-471-22153-8 Electronic 8 THE TELEPHONE NETWORK 8.1 INTRODUCTION The early history of the telephone system has been outlined in Chapter 1. The growth of the telephone system has been truly phenomenal and forecasts show a continuing growth as new services such as data transfer facsimile and mobile telephone are added. The telephone differs from the broadcasting system in two basic ways 1 In broadcasting a few people who in theory have information send it out to the many who are presumed to want the information it is one-way traffic. The communication link provided by the telephone is two-way traffic. 2 The basic idea of broadcasting is to make the message available to anyone who has the equipment and the interest to tune in. This is in contrast to the norm in the telephone system where the privacy of the message is guaranteed by law. Because of these differences the two systems handle very different types of information - public versus private - and their patterns of development have been different. 8.2 TECHNICAL ORGANIZATION For a telephone system to work there must be a minimum of two people who wish to communicate. It is then possible to install the circuit shown in Figure 8.1. This would be quite adequate except for the fact that these two people may not want to talk to each other all the time and therefore some additional system has to be set up for either person to indicate to the other that they wish to talk. What was 213 214 THE TELEPHONE NETWORK Figure 8.1. The basic elemental telephone system. added was a bell on the called party s premises which can be rung from the calling party s premises. Presumably the success of this prototypical communication system would soon attract the attention of other people who would want to set up similar systems. It is clear that soon the situation depicted in Figure 8.2 would develop .