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
David Davies (electrical engineer) (IEE) 1996-2001, President of the Royal Academy of Engineering He has subsequently been Chairman of Railway Safety, a non executive director of Lattice plc, a non-executive director of The ERA Foundation, Chairman of the Hazards Forum (2002-2010), and safety advisor to the Board of National Grid plc. The Sir David Davies building at Loughborough University, housing the electrical engineering department, is now named after him. David Davies (electrical engineer) Sir David Evan Naunton Davies , known as Den Davies or David "DEN" Davies, (born 1935) is a British electrical engineer and educator. He was knighted for services to science in