The practical telephone handbook and guide to the telephonic exchange (1906)
Poole, Joseph · New York, Macmillan Co. · leaf 175
ce of the aluminiumdisc. Mechanically-Restored Drops.— Sofar, the so-called self-restoringindicators described have been re-stored by the aid of electricity, butthere is another similar class of dropin which the restoring is done by mechanical means. In thisclass the indicator and connecting… … Fig. 166 a.—Scale f
Telephone
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