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 144
A to station B. The current in the mainline is, however, twice as strong as in the artificial line, and the THE TELEGRAPH 2,237 magnetic conditions produced on each side of the armatureN and N of the permanent magnets are such that the relayPR is held open and the relay PR is caused to close… … Pig. 3,085.—The dynamo polar duplex system. E and E are the dynamos, E for the positiveand E for the negative current. These supply their currents through resistance coilsR R either of German silver wire or of incandescent lamps. K is the key which closesthe local circuit of the walking beam pole…
Electrical engineering
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