Hawkins electrical guide ... : questions, answers & illustrations : a progressive course of study for engineers, electricians, students and those desiring to acquire a working knowledge of electricity and its applications ; a practical treatise (1914)
Hawkins, N. (Nehemiah), 1833-1928 · New York : T. Audel & Co. · leaf 313
Fig. 3,308.—Western Electric bell ringing transformer. A self contained unit for use on 60cycle alternating circuit of 100-125 volts. Delivers current at 6, 12, or 18 volts. Burglar Alarms.—A burglar alarm equipment consists ofmost of the apparatus required for regular electric call bell out-fits… … FlG. 3,309.—Yale lock burglar alarm switch. These switches are placed on the doors ofstores, residences, and other buildings connected with Burglar Alarm Systems, so thatpersons having the proper keys can go in or out of the buildings without ringing the alarm. about the same. Instead of push…
Electrical engineering
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