The practical telephone handbook and guide to the telephonic exchange (1906)
Poole, Joseph · New York, Macmillan Co. · leaf 161
•& * I \ \ f t. Fig. 151.—Connections for Exchange Line with 2 Extension Lines—Non Secrecy provided, which, by means of current derived from theexchange current supply, rings the ordinary trembler electric £XT. INST. 2 … Fig. 151a.—Three Extension Instruments without Intercommunication bell fitted in connection with the extension instrument. Forthese bells an extra line is needed between the main andeach of the extension instruments, These bells are wound to100 ohms resistance. SWITCHES AND EXTENSION INSTRUMENTS…
Telephone
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