Valve amplifier thermionic valves. The simplest valve was invented by John Ambrose Fleming while working for the Marconi Company in London in 1904 and named the diode, as it had two electrodes. The diode conducted electricity in one direction only and was used as a radio detector and a rectifier. In 1906 Lee De Forest added a third electrode and invented the first electronic amplifying device, the triode, which he named the "Audion". This additional "control grid" modulates the current that flows between cathode and anode. The relationship between current flow and plate and grid voltage is often represented as a series
Alexander Russell (electrical engineer) Alexander Russell (electrical engineer) Alexander Russell, FRS (15 July 1861 – 14 January 1943) was a Scottish electrical engineer and educator. He was born in Ayr, Scotland and educated at Glasgow University (gaining an MA in Mathematics and Physics) and Caius College, Cambridge. He was later (in 1924) awarded a doctorate. After teaching mathematics at Cheltenham College and the Oxford Military College, he took a post at Faraday House, in Southampton Row, London, which had been newly founded to train electrical engineers. In 1909 he became the Principal, a position he held until 1939. There he pioneered the sandwich course,