Vickipedia

PHONOGRAPH. This apparatus, invented in 1877 by Mr. Thomas A. Edison, an American electrician of note, differs from the vibrograph and phonautograph. The latter are constructed to record sound vibrations graphically, while Mr. Edison’s invention, which is properly called the ‘ Talking Phonograph,’ is designed to obtain such a record that the sound vibrations resulting from articulate speech can be mechanically reproduced at a distance of time. The invention, at the time these words are written, is only in the experimental stage, but it has been successfully exhibited both in America and in Britain. As originally made, the instrument consisted of three parts—the sender, the receiver or recorder, and the transcriber; but in the P. exhibited by Professor Fleeming Jenkin before the Royal Society of Edinburgh, the last apparatus was dispensed with, the sender being constructed to fulfil both functions. This sender consists of a tube, having an open mouth-piece at one end, and bearing at the other end a thin diaphragm of metal or other substance, with a sharp point or style affixed to the center of its outer surface.

The second apparatus consists of a cylinder, about four inches in diameter, having on its periphery a V-shaped groove, cut spirally from end to end. Over this grooved cylinder a sheet of tinfoil is placed, and the sender is advanced till the point of the style lightly touches the tinfoil, over the opening of the V-shaped cut. While the words to be recorded are spoken or sung, the cylinder is turned rapidly, the apparatus for moving it giving a lateral as well as a circular motion. The point of the style thus traverses the tinfoil spirally from end to end, and the vibrations in the diaphragm caused by the sounds, result in a series of indentations in the tinfoil. To reproduce the sounds in the ‘ transcriber’ (or in the ‘ sender ‘ under Professor Jenkin’s arrangement), the cylinder is again presented to a style attached to a diaphragm, the style being pressed against the tinfoil by a slight spring. The cylinder is now made to revolve, and the motion of the style upon the inequalities in the indented tinfoil produce vibrations in the diaphragm corresponding to the sound-caused vibrations originally created in the instrument by the voice. The sounds are thus reproduced with great exactness, but with a softening of the consonants which to some extent alters the character of the voice. If the tinfoil record of sung or spoken sounds be sent to a distance, or kept for a length of time, the original sounds can be reproduced on applying it to the proper instrument. It is stated that rubbings in tinfoil can be taken from a plaster-cast of the original indented slip, so that copies may be sent to different persons, all of whom can thus reproduce the sounds so long as their tinfoil copy remains intact. In using the P. to repeat sounds, the cylinder must be revolved at the same speed as at first, otherwise the pitch will be changed. For as sound is the result of air-vibrations at known intervals, if a speech spoken in a high key were reproduced slower at the repeating instrument, the result would be to convert a treble voice into a bass one, or vice versa, while the lower speed would convert smartly-spoken words into a drawl.