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 39
in ■SS-2g>,<g° rt w 2^^13S^c - <u 8 £ C oM- (D o e.B-9 >, ?G^o^dop v Bill 1 :&■ eo 7* ■♦s 5b fe 6 S >> CM ^ W CrQ Cfl Ur*l oc 2,132 HAWKINS ELECTRICITY Telephone Switchboards.—These are made in sections,called positions, for central offices. The requirements of suchexchanges… … TIP INCOMING RATRRY CURRENT Fig. 2,937.—Circuits of the original P. B. X. switchboard are shown for four pairs of cordwith the four cord relays and eight ringing keys. Four retardation coils are shown andthe plugs of the eight pairs of cord are represented. These circuits are connected to theother…
Electrical engineering
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