American telegraphy and encyclopedia of the telegraph; systems, apparatus, operation (1909)
Maver, William, jr. [from old catalog] · New York, Maver publishing company · leaf 463
DOUBLE-BALANCED RELAY THEORY. Fig. 293. The arrangement consists of two relays located in a central office of aProtective company. The main circuit is passed through each of these relays, … DOUBLE-BALANCED RELAY, which are wound to about 150 ohms each. One relay, d, is so adjusted that theslightest decrease in the current will permit its armature to be withdrawn; the otherI, is so adjusted that the least increase in the current will cause it to attract its arma- AUTOMATIC BURGLAR…
Telegraph
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