The standard electrical dictionary : a popular encyclopaedia of words and terms used in the practice of electrical engineering (1898)
Sloane, T. O'Conor (Thomas O'Conor), 1851-1940 · London : Crosby Lockwood and Son · leaf 525
Fig. 322. Single Needle Telegraph Instrument,Double Tapper Form, Fipr. 323. Double TapperKey for Single NeedleTelegraph. line; at rest both press against Z. If L is depressed so as to touchC, the current from the battery goes to the line by the key Z, goesthrough the coils of the distant instrument…
Electricity
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