Audion
![](/Images/godic/202412/22/Triode_tube_19063559.jpg")
![One of the earliest Audion radio receivers, constructed by De Forest in 1914. Audion tubes were mounted upside down, with the delicate filament hanging down, to prevent it from sagging and touching the grid. This was a detector (rectifier) and two stage audio amplifier unit; the radio signal came from a separate](/Images/godic/202412/22/Audion_receiver3559.jpg")
![(left) The first prototype Audion with the grid (zigzag wires) between the filament and plate.[11] (right) Later design of an audion tube. The grid and plate are in two parts on either side of the central filament. In both these tubes the filament is burned out.](/Images/godic/202412/22/First_internal_grid_Audion_tube3559.jpg")
![](/Images/godic/202412/22/Audion_tube3559.jpg")
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.