. Bulletin. Science. Figure 76.—Patent drawing of Runnings' carbon granule telephone transmitter. From patent 246512 (August 30, 1881). ther refined his approach by basing his experimenta- tion upon the fact that the apparent resistance of semi- conductors varied considerably with the pressure, and a few months later he created a successful transmitter. (See figs. 71, 72.) Edison filed the applications for the patents''^ on the first of his many forms of the carbon transmitter on April 1 and 27 and July 20, 1877. Basically Edison's transmitter consisted of a mass of carbon in various shap
. Bulletin. Science. Figure 76.—Patent drawing of Runnings' carbon granule telephone transmitter. From patent 246512 (August 30, 1881). ther refined his approach by basing his experimenta- tion upon the fact that the apparent resistance of semi- conductors varied considerably with the pressure, and a few months later he created a successful transmitter. (See figs. 71, 72.) Edison filed the applications for the patents''^ on the first of his many forms of the carbon transmitter on April 1 and 27 and July 20, 1877. Basically Edison's transmitter consisted of a mass of carbon in various shapes and textures, against which a vibrat- ing diaphram pressed. Change of pressure on the diaphram brought a change of resistance of the car- bon and so modulated the current. Edison's device soon proved to be better than Bell's magneto trans- mitter; and although it was insensitive by modern standards, shouting was no longer mandatory in order to carry on a telephone conversation. The Edison transmitter was rugged, and it gave a better quality of reproduction than Bell's Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Smithsonian Institution; United States. Dept. of the Interior; United States National Museum. Washington, Smithsonian Institution Press, [etc. ]; for sale by the Supt. of Docs. , U. S. Govt Print. Off
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