The practical telephone handbook and guide to the telephonic exchange (1906)
Poole, Joseph · New York, Macmillan Co. · leaf 588
so as to wind on a length, of hard steel wireof about 2 mils diameter by unwinding it from the otherbobbin. Between the other two bobbins the wire is guidedclose to the poles of two very small horseshoe electro-magnets—one of which, together with a second winding on the other one,is used for… … Fig. 504.—Poulsens Telegraphone, Steel Wire Type which is run past the magnets at the rate of about 10 feet persecond, the length being sufficient for about 30 minutes ofconversation. When the record has been made the motor is switched overso as to drive the other bobbin, and rewind the wire on the…
Telephone
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