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 315
TttMWDLYl Fig. 3,313.—House equipped with burglar alarm system. The spring contact switches areall connected in parallel. The door switches may be like that shown in fig. 3,309 inwhich the insertion of a key closes switch contacts in the lock. The battery and bellsare connected in parallel to the…
Electrical engineering
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