File:The practical telephone handbook and guide to the telephonic exchange (1906) (14569740537).jpg

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

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TelephoneCo. in this country. Four stations are shown connected toone line, and it is hence termed a 4-party line. Sometimesten or as many as twenty stations are connected on a singleline. The instruments are worked on the common-battery andautomatic signalling plan, the annunciator (or line relay)being operated and the calling lamp lit at the exchange, whens 269 270 PRACTICAL TELEPHONE HANDBOOK any one of the subscribers removes his receiver, and thuscloses the loop circuit to the battery. It will be noticed thattwo of the magneto-instrument bells are connected to the a wire of the loop and to earth. The other two bells are connectedto the b wire, and to condensers (of about 2 microfaradscapacity), the other terminals of the condensers being earthed.These condensers are used in order to prevent the closing ofthe loop circuit through the two sets of bells and the earthconnections, which would result in the operation of the linerelays and lamps. The same object may be attained by x-rH
Text Appearing After Image:
Fig. 276 raising the resistance of the bell branches to a very highfigure, such as 20,000 ohms, or more, so that the currentpassing through the line relay is insufficient to actuate it. The stations having their bells connected to the awire are designated by having X and 1, 2, 3, 4, or 5 addedto their ordinary fine number and those connected to theB wire have Y and 1, 2, 3, 4, or 5 also added. The stationsare called by code, a number of rings being given correspondingto their number on the wire—all the bells of the stations con-nected to the same leg of the loop being rung at the sametime, those on the other leg being undisturbed. The Xstation bells are rung by the regular ringing key of an ordinaryCJB. switch-board, but the Y stations require the con- PARTY-LINE WORKING 271 nections to be reversed, so as to connect the generator to theb wire of the loop. This is done by a second ringing key, as Answering Cord r2Eu-LT-Hi;#h

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