File:Carbon button microphone 1916.png

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English: Cross section drawing of a carbon button microphone|, 1916. This was the microphone used in the candlestick telephone, an early telephone used from 1904 to the 1940s. It consists of a cylindrical cell or "button" consisting of twe electrodes with carbon granules between them. The button was mounted on a metal strap, and the front face attached to a metal diaphragm in the mouthpiece. When someone spoke into the microphone, the sound waves were concentrated by the horn mouthpiece and vibrated the metal diaphragm back and forth. This put varying pressure on the carbon granules, varying their electrical resistance. A battery applied a voltage across the carbon cell, and the varying resistance modulated the current flowing through it. creating an audio signal.
Date
Source Retrieved April 17, 2014 from The New International Encyclopaedia, 2nd Ed., Dodd, Mead and Co., New York, Vol. 22, 1916, p. 64, fig. 4 on Google Books
Author Unknown authorUnknown author

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This media file is in the public domain in the United States. This applies to U.S. works where the copyright has expired, often because its first publication occurred prior to January 1, 1929, and if not then due to lack of notice or renewal. See this page for further explanation.
United States
United States
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