Mạng và viễn thông P14

Operator Assistance and Manual ServicesEarly telephone networkswere all manually operated.In 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.
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Mạng và viễn thông P14 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 networkswere all manually operated.In 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. In this chapter discuss we the operator assistance services which form a critical supplement to automatic switched services in meeting the high expectations of today’s telephone customer.14.1 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 14.1 illustrates an early manual switchboard,andFigure14.2atypicaltelephone used on sucha manualnetwork. Instead of anumbered dial there is just acradleforthehandsetandamagneto 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 alertingtheoperatorand lighting an opal (a light) ontheoperator’sswitchboard (Figure 14.1). 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 answertherequest,the operator uses one of the cords mounted on console part of the switchboard, which is the pulled out and plugged into the relevant jack socket immediately below the opal. The operator is now able to speak to the caller and ask for the name of the person he wishes to call. The operator records the caller’s name, the destination number and the time of day, on a ticket for later billing of the caller. The destination party is then alerted by the operator, whorings his telephone with another hand-cranked generator. The connection 281 z=$&.$282 ASSISTANCE OPERATOR MANUAL AND SERVICES Opals and Destination 0 Caller Operator Schematic l I /‘ Generator signalling crank Actual Figure 14.1 Early manual, or ‘sleeve control’switchboard is completed by plugging the other end of the cord into jack of the destination party. the In this way the pair of plugs and the cord connect the two corresponding line jacks to caller and destination. At the end of call the caller replaces the handset, extinguishing the the opal. On noticing this, theoperator removes the plugs and cord from the jacks, ready for use on another call. To make calls to customers on other exchanges the operator has a number of trunk line jacks. To use them, the operator must relay the call details to the operator on the second exchange, and forward the connection. The second operator either completes the call or forwards it to another operator, as necessary. In manual networks, setting up telephonecalls is highly labour-intensiv ...