The practical telephone handbook and guide to the telephonic exchange (1906)
Poole, Joseph · New York, Macmillan Co. · leaf 162
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… … Fig. 152.—Connections for Exchange and Extension Instrument—with Secrecy It will be noticed that only one condenser and one inductioncoil is used for the three instruments. Fig. 151a gives the connections of an arrangement for thesame purpose in which each instrument is provided with its
Telephone
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