Triode Triode A triode is an electronic amplifying vacuum tube (or "thermionic valve" in British English) consisting of three electrodes inside an evacuated glass envelope: a heated filament or cathode, a grid, and a plate (anode). Developed from Lee De Forest's 1906 Audion, a partial vacuum tube that added a grid electrode to the thermionic diode (Fleming valve), the triode was the first practical electronic amplifier and the ancestor of other types of vacuum tubes such as the tetrode and pentode. Its invention founded the electronics age, making possible amplified radio technology and long-distance telephony. Triodes were widely used in consumer
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