TELEPHONE. This instrument is designed to convey sounds to a distance by means of electricity. In 1860 Reis of Frankfort first recognized the principle of the telephone, using a membrane which, vibrating under the action of sound, caused pulsations of electricity to pass along the wire, and actuated the armature of an electromagnet, which, mounted on a sounding-board reproduced a sound corresponding in pitch and rhythm with the original. The quality of the sound was however entirely lost. There are several claimants for priority in the discovery of the principle of the articulating telephone, and the discoveries of Gray of Chicago, and Graham Bell, an Edinburgh gentle man resident in America, appear to have been nearly contemporaneous, and attained by different lines of study. The articulating telephone of Bell, which was first shown at the Philadelphia Centennial exhibition, is now of very simple construction. A small bar magnet, with a coil of wire over one end, is placed close behind a diaphragm of ferro type, the whole being inclosed in a case furnished with a mouthpiece. Words spoken into the telephone are reproduced faithfully on a similar instrument at great distances, and by use of the microphone (q.v.) the most minute sounds have been distinctly heard
and even magnified. Many extraordinary results have been achieved in conveying and reproducing sounds, and self-caught sounds from "induction" in the wires have pro duced interesting results. While the telephone is already very largely used in America for domestic and business communication, it has been less successful in Britain, the busier lines increasing the difficulties of induction. Three requirements appear .to be demanded to bring the telephone into general use, namely, a simple and reliable call or avertisseur, an increase of the sound to render it unnecessary to hold the telephone to the ear, and the removal of induction currents. Various methods for accomplishing each of these ends are now (1879) proposed, but the difficulties are not yet wholly over come. A controversy exists whether the sounds in the receiving telephone are vibra tory or molecular, or a combination of both.