The practical telephone handbook and guide to the telephonic exchange (1906)
Poole, Joseph · New York, Macmillan Co. · leaf 112
, as long as the outside circuit is complete to a battery. Fig. 78 shows a useful form of trembler in which the work-ing parts are covered and protected by the dome, thus making a very compact arrange-ment. Both points of contactbetween the vibratingspring and the end of screwshould be fitted with…
Telephone
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![An illustration from [Graphophone patents] (1878)](https://img.insideoutlibrary.com/img/200/ia-graphophonepaten20unit-1157-515.webp)
