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 63
cribe the operation of the inter-communi-cating system as shown in fig. 2,970. Ans. When central rings the auxiliary bell, the key C mustbe depressed to answer. If the call be for station two and hasbeen answered by station one, the transfer key, T, must firstbe depressed which throws the relay… … LEVtfti Fig. 2,968—Trunk selector system for automatic exchange, three groups of first selector havethe lines connecting in parallel except the first trunk line from each group, which is indi-vidual. First trunk line from A terminates at lever A2, second from B terminates at B2, andthird line from…
Electrical engineering
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