American telegraphy and encyclopedia of the telegraph; systems, apparatus, operation (1909)
Maver, William, jr. [from old catalog] · New York, Maver publishing company · leaf 672
MESSAGE HOOKS. « English * binding post; it affords a firm contact with the wire and is very suitablefor permanent connections. To prevent loosening of the contact upon the wire, as frequently happens inthe forms a c d, a set screw is generally provided in addition to the ordinaryscrew. 560…
Telegraph
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