The practical telephone handbook and guide to the telephonic exchange (1906)
Poole, Joseph · New York, Macmillan Co. · leaf 117
Fig. 83 … Fig. 84.—Scale i turn the crank b, some force is necessary before the arma-ture can be moved, and the result of applying this force isthat the pin a moves along the inclined face of the recess,withdrawing the end of the shaft from the spring j, againstwhich it is usually pressed by the spiral…
Telephone
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