American telegraphy and encyclopedia of the telegraph; systems, apparatus, operation (1909)
Maver, William, jr. [from old catalog] · New York, Maver publishing company · leaf 604
ithout a key, by any citi-zen, by turning the handle untilthe door opens, but, as the handleis turned, a loud gong is struckrepeatedly, giving notice to ad-jacent policemen, or others, thatthe box is being opened. The same box with the outsidedoor opened is shown in Fig. 371;the gong being… … * CHAPTER XXX. KAILWAY ELECTRIC BLOCK SIGNALING SYSTEMS, ETC. A block system, in brief, consists of a plan for the showing of sis^nals, manually,or automatically, which indicate to the engineer of an approaching train that a certainsection of the track in advance of him is clear or occupied. That…
Telegraph
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