Lee de Forest

220px-Lee_De_ForestLee de Forest (American; August 26, 1873 – June 30, 1961) An inventor credited with over 300 patents, his best known and most significant invention was the audio vacuum tube. This was a device that could take a weak electrical signal, such as a radio signal, and amplify it to a more useful level – such as to drive headphones or a loudspeaker. It built upon an earlier device called the Fleming Valve by adding a third electrode called a “grid” to control the amplification of the signal. The device was sold to the Federal Telegraph Company in Palo Alto where it was used to amplify telephone signals sent through transcontinental cables, and was further improved to work as an oscillator in the radiotelephone – an early invention to transmit voice and entertainment into households. In 1907 he formed the De Forest Radio Telephone Company for this purpose, and it became one of the early radio broadcast companies from which this industry grew. In 1919, De Forest filed his first patent on a sound-on-film process, which improved on the work of German inventors, and called it the De Forest Phonofilm process. It recorded sound directly onto film as parallel lines. These lines photographically recorded electrical signals from a microphone, which were translated back into sound waves when the movie was projected. He was given an Academy Award (Oscar) in 1959/1960 in recognition for this work. Read more…

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