American telegraphy and encyclopedia of the telegraph; systems, apparatus, operation (1909)
Maver, William, jr. [from old catalog] · New York, Maver publishing company · leaf 394
uitable electric eye, or receiver, when they fall upon it. The manner in which Prof. Hertz proceeded to show the existence of electricwaves in free space was, briefly, as follows: It was already known that electricoscillations could be set up in a well-insulated wire or conductor; in fact, that… … electric oscillator, shown in Fig. 254J. This consists of an ordinary large inductioncoil, I, the terminals of the secondary coil being connected to brass balls, orknobs, 11, and to Avhich short metal rods, or cylinders, w, are attached. The knobsare separated by a small air space or spark gap s,…
Telegraph
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