The
Audion was an electronic amplifying
vacuum tube invented by American electrical engineer
Lee De Forest in 1906. It was the first
triode, consisting of a partially evacuated glass tube containing three
electrodes; a heated
filament, a
grid, and a
plate. It is important in the
history of technology because it was the first widely used electrical device which could
amplify; a small electrical signal applied to the grid could control a larger current flowing from the filament to plate.