....of the two nails with the third which rests lightly on them. The movements which constitute the sounds are transferred to the conductors, modify the pressure and conduction at the points of contact; hence these variations which follow those of the noises, or of any sounds whatever emitted a short distance away, alter the battery currents in the wire, and act on the receiver of the telephone. Hughes noticed the advantage of employing, instead of metal contacts, the material carbon, which allows of a slight and constant pressure being put on the contacts, and is besides unoxidizable.
Credit :
Electricity and Magnetism, Amedee Guillemin, 1891.
