American telegraphy and encyclopedia of the telegraph; systems, apparatus, operation (1909)
Maver, William, jr. [from old catalog] · New York, Maver publishing company · leaf 306
porarily. CHICAGO branch OFFICE SIGNAL ARRANGEMENT. This arrangement was used at one time in a Chicagomain office, and is illustrated in Fig. 198. At the main office mo, k is a switch or key with upperand lower contacts. When on its upper contact the callbell CB is in circuit. Normally the keys in…
Telegraph
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