Tunzelmann, George William von, 1856- · New York, Scribner & Welford · leaf 127
s of a piano in order toproduce crotchets or quavers respectively. Another formof sounder, which is extensively used in America onrailways, and in other places where external noises areliable to interfere with the sound of the instrument, isshown in Fig. 28. This instrument has a very heavyarmature… … When the line is of any great length, the nnperfectinsulation will make the current too weak to work asounder without the use of a relay, the principle of whichwas described in the last chapter. OVERLAND TELEGRAPHS. S In its present form it consists simply of a more delicateform of electro-magnet…
Electric industries · Electricity
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