science · 17 January 1882 · 142 years ago
In 1882, Thomas A. Edison was issued a patent for an improvement to the telephone (No. 252,442). It described a carbon microphone. Finely divided conducting material, such as carbon, between metal cups mounted on arms is attached to the mouthpiece diaphragm. As sound waves directed through the mouthpiece move the diaphragm, the arms change the pressure on the carbon button which in turn varies an electric current passing through the carbon button. Changes in the current correspond to the pitch and amplitude of the sound. One arm conducts the electrical current to the carbon button, and the the other from it.
OnThisDay.net