English: American electrical engineer Lee De Forest, the inventor of the triode vacuum tube, with two of his tubes. De Forest's three electrode tube, which he invented in 1906 and called the "Audion", was the first electrical device which could amplify, and began the field of electronics. The small tube (left) was a low power one watt Audion used in radio receivers. The large tube (right) was a high power 250 watt tube used in radio transmitters, which De Forest called an "oscillion". De Forest began making it in 1919 so that may be the date of this picture.