. American telephone practice . 1877 Emile Berliner, of Washington, D. C, filed a caveat, andlater in the same year applied for a patent on a transmitter, depend-ing upon a principle pointed out in articles published in 1856, 1864and 1874 by the French scientist, Du Moncel, that if the pressure THE BATTERY TRANSMITTER. 15 between two conducting bodies forming part of an electric circuitbe increased, the resistance of the path between them will be dimin-ished, and conversely, if the pressure between them be decreased,a corresponding increase of resistance will result. Berliners transmitter is s
. American telephone practice . 1877 Emile Berliner, of Washington, D. C, filed a caveat, andlater in the same year applied for a patent on a transmitter, depend-ing upon a principle pointed out in articles published in 1856, 1864and 1874 by the French scientist, Du Moncel, that if the pressure THE BATTERY TRANSMITTER. 15 between two conducting bodies forming part of an electric circuitbe increased, the resistance of the path between them will be dimin-ished, and conversely, if the pressure between them be decreased,a corresponding increase of resistance will result. Berliners transmitter is shown in principle in Fig. 14, which is areproduction of the principal figure in his now famous patent. Inthis A is the vibratory diaphragm of metal, against the center ofwhich rests the metal ball, C, carried on a thumb-screw, B, which ismounted in the standard, d. The pressure of the ball, C, againstthe plate, A, can be regulated by ^turning the thumb-screw. Thediaphragm and ball form the terminals or electrodes of a circuit,. FIG. 14.—BERLINERS TRANSMITTER. including a battery and receiving instrument. Figs. 15 and 16show two different views of an exact duplicate of Berliners originalmodel as filed in the patent office. This was very roughly con-structed as shown. The diaphragm was a circular piece of ordi-nary tin and the contact-piece a common blued-iron wood action of this instrument (which at best has never been satis-factory or commercial) is as follows: when the diaphragm vibrates,the pressure at the point of contact, a, Fig. 14, becomes greater orless, thus varying the resistance of the contact and causing corre-sponding undulations in the current flowing. Soon after this Edison devised an instrument using carbon as themedium for varying the resistance of the circuit with changes ofpressure. Edisons first type of carbon transmitter consisted simplyof a button of compressed plumbago bearing against a small plati- 16 AMERICAN TELEPHONE PRACTICE.
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