The practical telephone handbook and guide to the telephonic exchange (1906)
Poole, Joseph · New York, Macmillan Co. · leaf 90
Fig. 51.—Scale \ RECEIVERS IN GENERAL USE 67 fied form, in which a compound flat steel ring (Fig. 52) ismagnetised across one of its diameters, n s. With the coils,etc., it is completely enclosed in a small metal case. Theresistance of the coils is usually about 120 ohms. The in-strument is very…
Telephone
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