The practical telephone handbook and guide to the telephonic exchange (1906)
Poole, Joseph · New York, Macmillan Co. · leaf 249
Fig. 244.—Testing Connections simplifiedP 224 PRACTICAL TELEPHONE HANDBOOK … mm i —^ of the calling side of a pair of cords when about to make anengaged test, and also shows two jacks of an unconnectedline with the cut-off relay,while Fig. 245 shows asimilar pair of jacks, onebeing connected to thethird conductor of a plugand cord. In the latter casethe engaged click would…
Telephone
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