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Diode and Triode Vacuum Tube Development

July 5th Fact-of-the-Day

University College (London) Professor John Ambrose Fleming was employed by the Marconi Company as a scientific consultant. While working in that capacity in 1904 he developed and patented a practical diode vacuum tube for use as an RF signal detector. He called his tube an Oscillation Valve, but others generally referred to it as the Fleming Valve. It was based on the Edison Effect discovered by Thomas Edison in 1883. (Edison created the first diode in 1883, but didn't understand how it worked or what it could be used for.) Two years after Fleming developed his diode, Lee De Forest (New York) added a control grid and invented the triode vacuum tube. Lee De Forest's triode could not only detect radio signals, it could amplify them; and because it could amplify, it could be used to make oscillators. De Forest's invention of the triode made it possible to advance from spark transmitters and diode detectors to circuits with vastly greater performance. ©2005 Martek International All rights reserved.


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