American telegraphy and encyclopedia of the telegraph; systems, apparatus, operation (1909)
Maver, William, jr. [from old catalog] · New York, Maver publishing company · leaf 597
working order the emergencycall is used, or the emergency call may be used in addition to the telephone message. No means are employed on tliis system to prevent the passage of box number sig-nals over the circuit from interfering with the use of the telephone ; the interruption,if any, being only… … Where it is desired to announce a special call by an extra alarm in the cen-tral office, additional devices may be added to those shown at CO in Fig. 361. Onesuch device, due to Mr. J. W. Stover, is outlined in Fig. 364. In this figure CO represents the central office in which g is the recording…
Telegraph
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