The practical telephone handbook and guide to the telephonic exchange (1906) (14569733207)

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:

, but if they appear on a green ground a recordis to be made on a ticket, and if on a red ground a fee is to bedemanded for the call. Markings on Multiple-Jacks.—When a subscriber has twoor more separate lines to the exchange an endeavour is made,as far as possible, to give consecutive numbers on the switch-board ; and in order to inform the operator of the fact a lineis painted under the jacks in the multiple section, so that she COMMON BATTERY MULTIPLE SWITCH-BOARDS 23? may connect to another line if one is engaged. The markingsgreatly assist the operators in their work. Automatic Night Lighting,—In order to economise theelectric-light current at night an arrangement known as theBelfast system is used in the more important exchanges. Anextra relay, a (Fig. 255), is included in the pilot lamp andnight-bell relay, N.B.R., circuit. When a subscriber lifts hisreceiver at night, the relay a is actuated, and closes a circuitin which is a powerful electro-magnet, E.M., when the double-

Text Appearing After Image:

Fig. 255 bar switch, D.B., is to the left. The armature of E.M. whenattracted closes the lighting switch, L.S., which lights a lampover the section on which the call is made. When the night operator inserts his instrument plug intothe instrument-)ack of the section, the relay b is brought intoplay, so as to take the place of relay a when the latter is cutout by the insertion of the answering plug into the jack ofthe calling line. In a magneto exchange the relay a is included in the night-bell circuit. CHAPTER XVIII JUNCTION-LINE WORKING Most large towns have several exchanges, as it is foundmore economical to have central offices in the various loca-lities than to run all the wires to one central office, althoughthe latter would constitute the ideal arrangement from theoperating point of view. It would, however, be subject tothe disadvantage that in the case of a fire at the one ex-change the whole of the telephonic system of the town wouldbe deranged. Again, the lengths of the subscr

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1906

Northeastern University, Snell Library

http://commons.wikimedia.org/

public domain