American telegraphy and encyclopedia of the telegraph; systems, apparatus, operation (1909)
Maver, William, jr. [from old catalog] · New York, Maver publishing company · leaf 565
ided withinthe box, at the lower left corner. The hand signaling key used in thisbox is shown separately in Fig. 339. Thecontact is made between the pin at the leftand the cone-shaped j^iece of metal c. Aspiral spring normally keeps the cone andpin in contact. When, however, the knobK is pushed… … FIG. 340.
Telegraph
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