143 



I append to this extracts from my specifica- 

 tion filed Feb. 14, 1876: 



To All Whom It May Concern : Be it known that I, Elisha 

 Gray of Chicago, in the County of Cook and State of Illinois, 

 have invented a new art of transmitting vocal sounds tele- 

 graphically, of which the following is a specification : It is 

 thr object of ray invention to transmit the tones of the hu- 

 man voice through a telegraphic circuit, and reproduce them 

 at the receiving-eud of the line, so that actual conversations 

 can be carried on by persons at long distances apart. I have 

 invented and patented methods of transmitting musical im- 

 pressions or sounds telegraphically, and my present inven- 

 tion is based upon a modification of the principle of said 

 invention, which is set forth and described in letters patent 

 of the United States, granted to me July 27, 1875, respectively 

 numbered 166,095 and 166,0%, and also in an application for 

 letters patent of the United States, filed by me, Feb. 23, 

 1875. * * * My present belief is that the most effective 

 method of providing an apparatus capable of responding to 

 the various tones of the human voice is a tympanum, drum, 

 or diaphragm, stretched across one end of the chamber, car- 

 rying an apparatus for producing fluctuations in the poten- 

 tial of the electric circuit and consequently varying in its 

 power. * * * The vibrations thus imparted are transmitted 

 through an electric circuit to the receiving-station, in which 

 circuit is included an electromagnet of ordinary construc- 

 tion, acting upon a diaphragm to which is attached a piece of 

 - !"; iron, and which diaphragm is stivtchrd across a receiv- 

 ing vocalizing chamber C, somewhat similar to the corres- 

 ponding vocalizing chamber A. 



The diaphragm at the receiving-end of the line is thus 

 thrown into vibrations corresponding with those at the 

 transmitting-end, and audible sounds or words are produced. 



The obvious practical application of my improvement will 

 be to enable persons at a distant- i<> ..nv.-rs.- \\ith each 

 hrough a telegraphic circuit. just as they now do iu 

 each other's presence, or through a speaking-tube. 



