Marconi-Fleming valve radio receiver, c 1908.
© Science Museum / Science & Society Picture Library
As well as being a pioneer in the application of electricity to lighting and heating on a large scale, John Ambrose Fleming (1849-1945) invented the thermionic diode or valve. His invention was a major step forward in wireles 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 Valves became fundamental components in radios, as well as television sets and computers for 50 years, before being superseded by the transistor. The Marconi-Fleming valve receiver was the first radio receiver to make use of Fleming's invention.