Electricity for everybody; its nature and uses explained (1895)
Atkinson, Philip · New York, The Century Co. · leaf 210
two of theinstruments, with the positive pole of one battery andthe negative pole of the other, as shown in Fig. 83; theremaining pole of each battery being connected, throughthe remaining instruments, by a short wire, with theearth, by which the circuit is completed. The earth, inthis case, is not… … Fig. 84. The Key.—The transmitting instrument is called akey, and is constructed as shown in Fig. 84, with a THE TELEGRAPH AND TELEPHONE. 195 hinged lever which can be depressed by an insulatingknob in opposition to a supporting spring, so as to bringinto contact two points, shown under the lever…
Electricity
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