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Lee De Forest, US inventor

Lee De Forest, US inventor

H406/0265

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Credit

LIBRARY OF CONGRESS / SCIENCE PHOTO LIBRARY LIBRARY OF CONGRESS / SCIENCE PHOTO LIBRARY

Caption

Lee De Forest (1873-1961), US inventor, on board a ship. De Forest studied at Yale, gaining his doctorate with a thesis on radio waves. In 1907 he patented the Audion tube (triode valve). This was an adaptation of a diode, with a third electrode between the cathode and anode. The Audion was used as a detector of radio signals, an amplifier of audio, and an oscillator for transmitting. In 1913, AT&T installed audions to boost voice signals as they crossed the US continent, and not long after, they were being used in radios. This photograph is from the Bain News Service, one of the USA's earliest news picture libraries. The photographs date from the 1890s to the 1930s.

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