Flemings oscillation valve, 1904.

UNITED KINGDOM - APRIL 15: Replica of the original oscillation valve made by John Ambrose Fleming (1849-1945), an English physicist and electrical engineer. As well as being a pioneer in the application of electricity to lighting and heating on a large scale, Fleming invented the thermionic diode or valve. His invention was a major step forward in wireless technology as it was considerably more efficient as a radio wave detector than coherers or magnetic detectors. Valves became fundamental components in radios, as well as television sets and computers for 50 years, before being superseded by the transistor. (Photo by SSPL/Getty Images)