Lee De Forest. Portrait of American physicist,engineer and radio pioneer Lee De Forest (1873- 1961). He is holding a phonofilm motion picture camera. This camera,which he invented in 1920,was used in the first film with sound,The Jazz Singer,in 1926. De Forest gained his doctorate at Yale University,USA,with a thesis on radio waves. In 1907 he patented the Audion tube,a thermionic triode valve. This adapted diode had a third electrode between the cathode and anode. The triode amplified weak signals,allowing the practical development of radio broadcasting and the first computers. Triodes were eventually replaced by solid-state devices |