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Lee De Forest. Portrait of Lee De Forest (1873- 1961), American radio pioneer, holding the triode valve that he invented. De Forest studied at Yale, gaining his doctorate with a thesis on radio waves. In 1907 he patented the Audion tube, a thermionic triode valve. This was an adaptation of a diode, having a third electrode between the cathode and anode. The triode proved useful in amplifying weak signals and allowed the practical development of radio broadcasting and the first computers. The triodes were eventually replaced by solid-state devices. De Forest also developed a system for film soundtrack recording and a medical diathermy machine.
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