American telegraphy and encyclopedia of the telegraph; systems, apparatus, operation (1909)
Maver, William, jr. [from old catalog] · New York, Maver publishing company · leaf 462
the safety magnet, apin plug, inserted by the inspector at 2, will elicit that information. A pinplaced in 3 will test the condition of the door and window contacts. BfJRGLAR AI^RM AND DISTRICT MESSENGER CALL BOX COMBINATION. Sometimes it is desired to utilize existing district service call boxes… … COMBINATION CALL AND BURGLAR ALARM BOX. then sends in the number of the box to the central office; itbeing understood that ihe box signaling apparatus had been previ-ously wound in the usual manner, by means of the crank leverJ, seen in Fig. 295^, and that the pallet had then been set bypushing up…
Telegraph
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