American telegraphy and encyclopedia of the telegraph; systems, apparatus, operation (1909)
Maver, William, jr. [from old catalog] · New York, Maver publishing company · leaf 308
JBram:^ Q/fcce^ Loop … THE HURD BRANCH OFFIFE CELL. tlv^ drop to give an audible signal. By having the 3-point switch connected to bothsMes of the relay the cutting out of that instrument is insured in the event of a trans-position of the sides of the loop in the main office. This device gives very satisfactoryresults.…
Telegraph
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