The practical telephone handbook and guide to the telephonic exchange (1906)
Poole, Joseph · New York, Macmillan Co. · leaf 74
naturethat they so affected the attraction between the magnet andthe steel spring of the receiver as to set up exactly correspond-ing movements in its diaphragm to those impressed upon thatof the transmitter. These movements being impressed uponthe air, a person listening at the end of the cylinder… … Fig. 34 he arrived at the instrument shown in Figs. 34 and 35, wherea compound horseshoe permanent magnet, a, took the placeof the original electro-magnet, two small coils of wire, B b,being fixed on soft-iron pieces attached to its poles. It hadbeen found that no battery was required, its only use…
Telephone
Internet Archive · Northeastern University Library · Public Domain Mark 1.0. Free to use for anything.
![An illustration from [Graphophone patents] (1878)](https://img.insideoutlibrary.com/img/200/ia-graphophonepaten20unit-501-223.webp)
