The practical telephone handbook and guide to the telephonic exchange (1906)
Poole, Joseph · New York, Macmillan Co. · leaf 229
--£ Fig. 229 the test wire and all the bushes T of that number are therebyconnected to earth, and will give the test click in the operatorsreceiver when the tip of the plug is touched on to it, as shownin Fig. 229. As previously mentioned, it is necessary to lock SWITCH-BOA RDS—MA GNETO-BRA NCHING…
Telephone
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