English: Early French military triode vacuum tube patent no. 452657, October 1915. The triode was invented by American engineer Lee De Forest in 1906, who held the rights, but in 1912 he let his French patent rights lapse due to lack of a $125 fee. The French government manufactured hundreds of thousands of these sturdy tubes, called the Loupiote, during World War 1. The tube consists of an evacuated glass bulb containing three electrodes: a heated filament, a fine horizontal tungsten wire, surrounded by a concentric helix of wire called the grid, surrounded by a concentric metal cylinder called the plate.