Lee de Forest was an American inventor, self-described “Father of Radio,” and a pioneer in the development of sound-on-film recording used for motion pictures. His most famous invention was, in 1906, an “Audion” (triode) vacuum tube, the first practical amplification device.

The invention had great potential as a telephone repeater amplifier. Previously, electromechanical note magnifiers had been used by the telephone industry, with little success.