The practical telephone handbook and guide to the telephonic exchange (1906)
Poole, Joseph · New York, Macmillan Co. · leaf 520
PILOT RELAY ■h^ll-HH-Ih l V. 12 V. Y 12 V. 12 V. Fig. 461.—Time Check (Reproduced from Electrical Engineering by permission of the Proprietors) arm ca clear of wheel w. If on the other hand an extensionof time is required the operator presses twice on the key, thefirst restores as above and the…
Telephone
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