Elementary radio tube developed by Lee De Forest (patented 1907).
It was the first triode vacuum tube , incorporating a control grid as well as a cathode and an anode. It was capable of more sensitive reception of wireless signals than were the electrolytic and Carborundum detectors then in use. The Audion made possible live radio broadcasting and became the key component of all radio, telephone, radar, television, and computer systems before the invention of the transistor .