de Forest, Lee (1873–1961)
Lee de Forest was a US inventor of the audion triode valve (see electron
tube). This three-electrode valve, invented in 1907, was one of the most
important inventions in electronics. It could amplify signals, and had numerous
applications. Valves became essential in radio, television, radar, computer
and other electronic systems, and remained so until the transistor was invented in 1947.