The practical telephone handbook and guide to the telephonic exchange (1906) (14776121953)

Identifier: practicaltelepho00pool (find matches)

Title: The practical telephone handbook and guide to the telephonic exchange

Year: 1906 (1900s)

Authors: Poole, Joseph

Subjects: Telephone

Publisher: New York, Macmillan Co.

Contributing Library: Northeastern University, Snell Library

Digitizing Sponsor: Boston Library Consortium Member Libraries

Text Appearing Before Image:

Fig. 464, taken from an article by M. Kamsey in the firstnumber of The Post Office Engineers Journal, shows thegeneral connections of the cord circuit of a subscribers section.It will be seen that the speaking current from a 40-volt battery 5oo PRACTICAL TELEPHONE HANDBOOK is fed through two coils wound on the same core, so that theC.B. system adopted is that of Stone. The double coil lastmentioned with another single winding coil which is connectedin the third or sleeve conductor of the connecting cord, to-gether form a compound supervisory relay. The lamps lightup when the single coil in the third conductor only is energisedand the feeding current has ceased through the double woundcoil owing to the subscriber having hung up his receiver. Aslong as both single and double coils are energised the relay isnon-operative. As in the case of the British Insulated Co.ssystem at Cardiff and elsewhere, the speaking connectionbetweenthe connected subscribers is established through condensers.

Text Appearing After Image:

Fig. 464.—Cord Circuit, Glasgow Central Exchange Most of the other details are on similar lines to those of theWestern Electric Co.s system, as are also the subscribersinstrument and line circuits, so that further description isunnecessary. * W. E. Co.s No. 9 C.B. Switch-Board.—This is a type ofswitch-board made up in one-position sections and installed inexchanges where the ultimate number of direct subscriberslines will not for a considerable period exceed 800. A front view of a section is shown in Fig. 465. It is com-plete in itself and arranged for a single operator. A boardmade up of these sections is employed in exchanges where butlittle junction or trunk work is required. As the rate ofcalling where such a board is needed is generally small and * See also a very full account by J. W. Turner in th? Post OfficeEngineers Journal for January 1910. SPECIAL EXCHANGE SYSTEMS 501 the operators employed will necessarily be in excess in pro-portion to the calls—in order that suffic

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1906

Northeastern University, Snell Library

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public domain