First Audion tubeIn 1906, the first triode was ordered by Lee de Forest who instructed the New York automobile lamp maker, H. W. Candless, to make a glass bulb containing a "grid" wire between a filament and an electrode plate. These specifications extended the Fleming two-element diode valve design previously published in the Proceedings of the Royal Society. The third element - the grid wire - regulated the flow of electrons between the filament and the anode plate, producing an amplification of the variations in a signal voltage applied to the grid. De Forest named his invention the "Audion." Within a few years (1913-1917) he was able to profit from his patents that he sold to AT&T for a total of $390,000.«[Image: A de Forest Audion tube, circa 1912.] |
