The telephone: an account of the phenomena of electricity, magnetism, and sound, as involved in its action (1877)
Dolbear, A[mos] E[merson], 1837- [from old catalog] · Boston, Lee & Shepard; New York, C. T. Dillingham · leaf 123
FIG. 14. — MY FIRST SPEAKING TELEPHONE. wound with cotton-covered copper wire, No. 23, each bobbin contain-ing about 150 feet.This magnet, with thebobbins slipped uponits poles, was made fastto a post two or threeinches high. The steelwas made as stronglyFIG. 14.—END VIEW. magnetic as was possi-… … HOW TO MAKE A TELEPHONE. 119 weight. In front of the poles, a sheet of thinsteel, one-fiftieth of an inch thick, was made fastto an upright board having a hole cut through itthree and a half inches in diameter (Fig. 14, endview) ; the plate was screwed tightly to this board,so as to cover the hole…
Telephone
Internet Archive · Prelinger Library · Public Domain Mark 1.0. Free to use for anything.
