Audion

The Audion was one the first electronic devices able to increase sounds. It was invented by American inventor Lee de Forest in 1906.^[1][2][3] It was a glass tube with no air inside. It contained three parts: a filament, a plate, and a grid.

Triode Audion vacuum tube from 1908. The filament (which was also the cathode) was at the lower left inside the tube but has burned out and is no longer present. The filament's connecting and supporting wires are visible. The plate is at the middle top, and the grid is the serpentine electrode below it. The plate and grid connections leave the tube at the right.

It was the first functional electronic amplifier. It replaced older technologies, such as the coherer used in early radios. It enabled live radio broadcasting for the first time.^[4]