The practical telephone handbook and guide to the telephonic exchange (1906)
Poole, Joseph · New York, Macmillan Co. · leaf 112
Fig. 78.—Scale k go PRACTICAL TELEPHONE HANDBOOK Magneto Switch-Bells.—In the early days of the telephone,batteries were almost exclusively used for signalling purposes,but they were soon superseded by mechanical generators ofelectricity, based on Faradays discovery that currents couldbe generated…
Telephone
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