The practical telephone handbook and guide to the telephonic exchange (1906)
Poole, Joseph · New York, Macmillan Co. · leaf 183
t exceeded unless ex-cessive force is used. If a spiral should break, the two brokenends are drawn apart, and, consequently, no microphoniccontacts are formed. Fig. 178 shows how the cords areconnected to the plugs. From a comparative test, it was found that, with veryrough handling, the number of…
Telephone
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