The practical telephone handbook and guide to the telephonic exchange (1906)
Poole, Joseph · New York, Macmillan Co. · leaf 119
Fig. 86 Scale Fig. 87 which the moving parts are magnetic in themselves, or aremaintained in a magnetic state by the induction of magnets.The well-known Siemens relay is constructed on this prin-ciple, and a modification of it was adopted to form the polarisedbell. Figs. 86 and 87 represent a…
Telephone
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