American telegraphy and encyclopedia of the telegraph; systems, apparatus, operation (1909)
Maver, William, jr. [from old catalog] · New York, Maver publishing company · leaf 310
the 260 I.OOP SWITCHES. 261 outer tube, being insulated therefrom; nor do screws n, 2, come in contact witb the in-ner tube. Thus, when the plug is inserted in a spring-jack, the inner tube is connecter]with a pin at 7 or 3, and the outer tube with the spring at 7 or 3. The handles h, hof the plugs… … J A i 1 M Ze^ POSTAL LOOP SWITCH. the neutral relay, r s the repeating sounder, etc. The tubes of w are connected perma-nently to the wires running to the branch office. Wires leading from loop batteriesb and B are connected to the tubes of w. Wires leading from the 3-point switches sS are…
Telegraph
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