History, theory, and practice of the electric telegraph (1866)
Prescott, George B.(George Bartlett),1830-1894 · Boston, Ticknor and Fields · leaf 179
olonged,in order to bring the indicat-ing-needle upon the sign tobe shown at a distance, orthe movable dial to the placewhere the sign is to be found.In the dial telegraphs thereis always an electro-magnet, A, which, acting upon an armature,or, as it is called, a contact of soft iron, B, produces… … Fig- 71. THE DIAL TELEGRAPHS. 161 the electro-magnet, the action of which is arrested and liberatedaccording to the position of the piece. The inconvenience ofsome of the dial telegraphs is, that, in general, each signal inthem being dependent upon those which go before it, errors areliable to…
Telegraph
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