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 47
nd B boards. Ans. When a subscriber lifts the receiver, an electric light 2,140 HAWKINS ELECTRIC ITY glows at the A board, the operator inserts a back plug in thecorresponding jack, ascertains the number, passes it on to theB operator through the front plug of the pair of cord used, theB operator… … Fig. 2,946.—Transfer circuit. Transfer circuits are used as trunk lines between local andtoll boards, in which case order wires are installed for communication between operatorsin ordering up connections. Each end of a transfer circuit or order wire circuit terminatesin a lamp and associated jack.…
Electrical engineering
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