American telegraphy and encyclopedia of the telegraph; systems, apparatus, operation (1909)
Maver, William, jr. [from old catalog] · New York, Maver publishing company · leaf 550
ions of this signal box will be shown more in detail in subsequent diagrams. What has been thu8 far said relates almost entirely to the sending in of alarmsto a central office; and the simplest apparatus required for the reception of an alarmhas been shown in Fig. 326. Much more than this, however,… … FIRE ALARM STRKET BOX, number of signal boxesis greater than is deemedadvisable to place on onecircuit and, therefore, anumber of separate cir-cuits emanate from thecentral office. This neces-sitates the employmentof devices to repeat alarmsreceived on any one circuitDver all of the other…
Telegraph
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