Radio receiver crude triode, was invented in 1906 by Lee De Forest as a more sensitive detector for radio receivers, by adding a third electrode to the thermionic diode detector, the Fleming valve. It was not widely used until its amplifying ability was recognized around 1912. The first tube receivers, invented by De Forest and built by hobbyists until the mid 1920s, used a single Audion which functioned as a grid-leak detector which both rectified and amplified the radio signal. There was uncertainty about the operating principle of the Audion until Edwin Armstrong explained both its amplifying and demodulating functions in a
John Snell (electrical engineer) General Charles Edmund Webber on electrical supply projects in Kensington and a number of country houses, before entering municipal service in London in 1893 as assistant electrical engineer in St Pancras during the construction of the Kings Road power station. In 1896 he transferred to Sunderland as Borough Electrical Engineer, additionally becoming Borough Tramways Engineer in 1896 after which he converted the tramway system to electric power. In 1906 he set up in business as a consulting engineer in Westminster, amalgamating with Preece and Cardew to form Preece, Cardew and Snell. During that time he served as an expert witness