Triode were invented, Philipp Lenard used the principle of grid control while conducting photoelectric experiments in 1902. The first vacuum tube used in radio was the thermionic diode or Fleming valve, invented by John Ambrose Fleming in 1904 as a detector for radio receivers. It was an evacuated glass bulb containing two electrodes, a heated filament and a plate (anode). Triodes came about in 1906 when American engineer Lee De Forest and Austrian physicist Robert von Lieben independently patented tubes that added a third electrode, a grid, between the filament and plate to control current. Von Lieben's partially-evacuated three-element tube, patented
William Bryson (electrical engineer) had offices at 16 Queen Charlotte Street in Leith. He died on 9 July 1906. He is buried in Warriston Cemetery. The grave lies on the diagonal path joining the lower vaults to the sealed eastern entrance. The stone is currently (2018) vandalised and is lying on the ground in undergrowth. William Bryson (electrical engineer) William Alexander Bryson FRSE (2 March 1855 – 9 July 1906), was a Scottish electrical engineer. He was born on 2 March 1855, the son of Alexander Bryson and Elizabeth W. Gillespie. His grandfather was Robert Bryson. His mother died shortly after he was born,