reproduce electrically an exact copy of the atmospheric vibrations produced by any sound whatever.
During a visit in Milwaukee at this time, Mr, Gray saw for the first time a toy called the lovers' telegraph, consisting of a membrane stretched over the end of a tube, and having a thread attached to the center, the other end of which was attached to a similar membrane. The fact that spoken words were distinctly transmitted by the longitudinal vibrations of the thread from one membrane to the other confirmed the idea that he had formed a year previous; and it immediately solved in his mind the problem of making a transmitter that would copy electrically the physical vibrations of the air produced by articulate sounds. He determined to put this into practical shape, and file it in the records of the Patent-Office. He accordingly put his speaking telephone into the form of drawings and specifications, and filed them in the United States Patent-Office, February 14, 1876. In his specification he states that he has invented a new art of telegraphically transmitting vocal sounds whereby the tones of the human voice can be transmitted through a telegraphic circuit, and reproduced at the receiving end of the line, so that actual conversations can be carried on by persons at long distances apart, and that he has devised an instrument capable of vibrating responsively to all the tones of the human voice, and by which they are rendered audible.
His method of providing an apparatus capable of responding to the various tones of the human voice was a diaphragm stretched across one end of a chamber, carrying an apparatus for producing fluctuations in the potential of the electric current, and consequently varying in its power. The vibrations thus imparted were to be transmitted through an electric circuit to the receiving station, in which circuit was included an electro-magnet of ordinary construction, acting upon a diaphragm to which was attached a piece of soft iron, and which diaphragm was stretched across a receiving vocalizing chamber, similar to the corresponding vocalizing chamber at the transmitting end.
This is the first description on record of an articulating telephone which transmits and reproduces the spoken words of the human voice at a distance by means of electricity, and instruments constructed in exact accordance with Mr. Gray's drawings and specifications, filed at the time above stated, are good articulating telephones. Moreover, Mr. Gray's method of producing articulate speech by varying the resistance of a battery current is much more effective than that of Professor Bell subsequently invented, which depends upon magneto-induction currents generated by the action of the voice, as is fully proved by the great superiority of Edison's carbon telephone, which is based upon this principle.
