File:American telephone practice (1905) (14753115011).jpg

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

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thelamp, which will therefore be lighted. A ringing and listening key are shown at the right-hand portionof this figure, and need no description. The operators transmitterreceives current constantly from the battery through a 140-ohm re-tardation coil and the primary of the induction coil. Bridged acrossthe circuit from ground to a point between the transmitter and theretardation coil is a two-microfarad condenser for the purpose ofallowing the fluctuation set up by the transmitter to circulate inthe circuit formed by the condenser and the primary winding of theinduction coil without passing through the retardation coil. Theconnections of the secondary winding of the operators inductioncoil and the operators head receiver are made in the usual man-ner. Bridged across the secondary side of the operators talking THE COMMON BATTERY MULTIPLE SWITCH-BOARD. 317 circuit is an order wire key adapted to make connection betweenthe operators telephone set and an order-wire circuit, for the pur-
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pose of allowing the operator to communicate with some other oper-ator, usually at a distant exchange, for purposes that will be pointed 318 AMERICAN TELEPHONE PRACTICE. out in subsequent chapters. The supervisory relays are shunted inall cases where they are placed in the talking circuit by a non-in-ductive resistance of about 30 ohms, this resistance being woundon the relay spool in addition to the active winding. A non-in-ductive path for the voice currents is thus afforded around therelay windows. In Fig. 266 the cord circuit of Fig. 265 is shown connecting two ofthe line circuits of Fig. 264. While the arrangement of the appa-ratus of the line circuits of this latter figure differ slightly in appear-ance, it will be seen that the actual circuit connections are the same,the change having been made in the diagrammatic arrangement forthe purpose of giving a clearer understanding. Considering the line at the left to be thai of the calling subscriber,and the line at the right that of

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