Modern practice of the electric telegraph. A handbook for electricians and operators (1872)
Pope, Frank L. (Franklin Leonard), 1840-1895 · New York : D. Van Nostrand · leaf 52
63. Fig. 20 represents a Ground Switch (58). The lever THE MORSE, OR AMERICAN TELEGRAPHIC SYSTEM. 30 A is attached to a wire leading to the earth, and the twostuds, B, C, are connected to the line wire on each sideof the instruments. … 64. THE PLUG SWITCH is shown in fig. 21. This ar-rangement consists of a brass spring, brought veryfirmly against a stationary pin. A wedge or plug madeof two pieces of brass, separated by an insulating mate-rial, is made in the form shown, to admit of insertionbetween the spring and the pin. The…
Telegraph
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