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 39
ng 20 or 30 miles, a register, whose coils arewound with No. 30 copper wire, may be worked by theline current, if the line be well insulated (57). 55. When the insulation is defective, or the circuitso long that its resistance renders the current too weakto work a register direct, as is usually the… … FIG. 12. 56. THE RELAY MAGNET.—The construction of therelay is shown in fig. 12. M is the electro-magnet,
Telegraph
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