tailieunhanh - Mạng và viễn thông P14

Operator Assistance and Manual Services Early telephone networkswere all manually the 1950s automatic networks began to take over, but even today they havefailed to supplant all manual ‘assistance services’. In the public network human operators provide a ‘safety net’ of assistance and advice for customers, and in some private networks human PBX operators are still employed to answer incoming calls from the public network and to connect them to the required extension. | Networks and Telecommunications Design and Operation Second Edition. Martin P. Clark Copyright 1991 1997 John Wiley Sons Ltd ISBNs 0-471-97346-7 Hardback 0-470-84158-3 Electronic 14 Operator Assistance and Manual Services Early telephone networks were all manually operated. In the 1950s automatic networks began to take over but even today they have failed to supplant all manual assistance services . In the public network human operators provide a safety net of assistance and advice for customers and in some private networks human PBX operators are still employed to answer incoming calls from the public network and to connect them to the required extension. In this chapter we discuss the operator assistance services which form a critical supplement to automatic switched services in meeting the high expectations of today s telephone customer. MANUAL NETWORK OPERATION In a manual network the connection of caller to destination is carried out by human operator. This is done by plugging cords into individual line sockets or jacks one jack corresponding to each possible destination user. Figure illustrates an early manual switchboard and Figure a typical telephone used on such a manual network. Instead of a numbered dial there is just a cradle for the handset and a magneto generator to call the operator. The routine for making a call on a manual network is as follows. The caller lifts the handset and rings the magneto generator by turning the handle. This has the effect of alerting the operator and lighting an opal a light on the operator s switchboard Figure . In some cases the operator was alerted merely by rattling the cradle. This had the effect of flashing the opal. There is an opal above each incoming line jack indicating precisely which caller wishes to make a call. To answer the request the operator uses one of the cords mounted on the console part of the switchboard which is pulled out and plugged into the relevant jack socket immediately .