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 547
iew until the train has left the block, when it automatically restores tothe position showing clear, as in fig. 3,726. Relays for Railway Signals.—There are four kinds of relayused for signaling; these are classed as 1. Polarized; 2. Neutral; 3. Interlocking; 4. Time. These are shown in the… … Fig. 3,727.—Polarized relay, wall type, with four front and four back neutral contacts and twofront and two back polar contacts. The armature of this relay is itself a permanentmagnet and swings back and forth to either pole of the electromagnet as the currentattracts and repels it or whenever the…
Electrical engineering
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