File:American telephone practice (1905) (14756285825).jpg

Identifier: americantelepho00mill (find matches)
Title: American telephone practice
Year: 1905 (1900s)
Authors: Miller, Kempster B. (from old catalog)
Subjects:
Publisher:
Contributing Library: The Library of Congress
Digitizing Sponsor: The Library of Congress

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FIG. 283.—DETAILS OF AMERICAN ELECTRIC CIRCUIT. The talking circuit between two such lines is shown in simplifieddiagrammatic form in Fig. 283, the two sides of the cord being di-vided by two two-microfarad condensers in order to prevent thesignals on the answering side from interfering with those on thecalling side, and vice versa. Referring again to Fig. 280, it will be seen that both supervisorylamps will remain dark as long as the subscribers are talking, but assoon as either subscriber hangs up his receiver the armature of relayS or S, will drop back, thus closing the circuit of the relay, B or B,which relay will then receive current over the following circuit:From the ungrounded pole of the battery through the retardationcoil, R, of the line with which the corresponding plug is connected.thence through the sleeve contact of the jack and plug to the backcontact of the relay, S* or S, and to ground through the coil of the
Text Appearing After Image:
350 THE COMMON BATTERY MULTIPLE SWITCH-BOARD. 351 relay, B or B. Upon the actuation of the relay due to this currentthe circuit of the corresponding supervisory lamp will be complete,which lamp will light and remain lighted until the operator pullsdown the connection. The test of this circuit appears to be faulty for the same reasonas pointed out in connection with the International circuit: That is,the test ring is constantly in connection with the line, and thereforeis subject to all the uncertainties as to its electrical condition as isthe line itself. The test ring, however, in this case, is maintainedunder normal conditions at a constant potential due to its beingpermanently connected to the underground side of the 40-volt bat-tery. When a plug, is inserted into the jack, however, or when a sub-scribers receiver is removed from its hook the potential of this testring is altered, due to the flow of current over the line or over thecord circuit and to the consequent drop of potenti

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