Lessons in practical electricity; principles, experiments, and arithmetical problems, an elementary text-book (1902)
Swoope, Coates Walton. [from old catalog] · New York, D. Van Nostrand company · leaf 351
l is grounded. Fig. 302. Atelegraph key, Fig. 298, is introduced into the primary circuitof the induction coil, whereby the dot and dashS3^stem of signals may be used. Details of the receiving appa-ratus are shown in Fig 302. A small glass tube (say ^ inchinside diameter) contains two plugs of…
Electricity · Magnetism
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