Telegraph engineering : a manual for practicing telegraph engineers and engineering students (1922)
Hausmann, Erich, 1886- · New York : D. Van Nostrand Company · leaf 101
uit permits of the simultaneous transmission oftwo independent messages over one wire in the samedirection, which transmission is called diplex signalHng.Key X is a form of continuity-preserving pole-changer,which, when depressed, causes its lever contact a to raisethe upper spring u away from the… … Fig. I. the circuit. Both keys are normally held in their upperpositions by retractile springs. Relay i? is a neutral relaywhich has its spring so adjusted that the armature will notbe attracted when the small current, supplied by the left-hand part, or short end, of the battery traverses the…
Telegraph
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