. An elementary book on electricity and magnetism and their applications. oked after by one operator. The lines are connectedto a drop and a spring jack in their proper sections so that theoperator may communicate with the subscribers by means ofher telephone addition toentering its ownsection through adrop and springjack, each sub-scribers line isalso connected toa spring jack inevery other sec-tion. Conse-quently, each op-erator attends tothe calls of a lim-ited number ofsubscribers whoselines are con-nected to dropsin her section, and, since all other lines have spring jacksin her se
. An elementary book on electricity and magnetism and their applications. oked after by one operator. The lines are connectedto a drop and a spring jack in their proper sections so that theoperator may communicate with the subscribers by means ofher telephone addition toentering its ownsection through adrop and springjack, each sub-scribers line isalso connected toa spring jack inevery other sec-tion. Conse-quently, each op-erator attends tothe calls of a lim-ited number ofsubscribers whoselines are con-nected to dropsin her section, and, since all other lines have spring jacksin her section, she can connect any of her subscriberslines to the line of any other subscriber which enters theexchange. Figure 386 shows the principle of the multiple board. Thedots marked local jacks in each section represent the springjacks belonging to the lines which are looked after by theoperator at the section. The drops, the keys for ringing upsubscribers, the operators telephone set, etc., are omitted from ORDINARY JACKS LOCAL JACKS .TloILj RY JACKS ypLuGs^ CAL JACKS. SECTION NO. SECTION NO. 3 SECTION NO. 2 EXCHANGE Fig. 386. — Diagram of multiple switchboard. 532 ELECTRICITY AND MAGNETISM the figure for the sake of simplicity. The dots marked ordi-nary jacks represent the multiple spring jacks, by means ofwhich the operator may connect any one of her subscriberswith any other that is connected with the exchange. It willbe seen, for instance, that subscribers lines, Numbers 1, 2, and3, enter the local jacks of section Number 1, but they also enterthe ordinary jacks of the other sections. If an operator inthe second section wishes to connect one of her wires, sayNumber 6, with one of those belonging to the first section, sayNumber 3, she is able to do so at once on her part of the board,as shown in the figure. An ingenious arrangement by which the operator can tellwhen a line is busy prevents switching three subscriberstogether. Exchanges with multiple switchboards have been
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectmagnetism, bookyear19
