American telegraphy and encyclopedia of the telegraph; systems, apparatus, operation (1909)
Maver, William, jr. [from old catalog] · New York, Maver publishing company · leaf 463
Another arrangement for indicating any change in the condition of a buro^lar 3B8 AMERICAN TELEGRAPHY. alarm circuit, known as a double balanced relay, is shown diagramatically in Fig.206. This instrument performs a practically similar office to that of tlae galvanometer, FIG. 296. … 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,
Telegraph
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