Lee de Forest
Videos
Lee de Forest was an American inventor, electrical engineer, and early pioneer in electronics of fundamental importance. He invented the first practical electronic amplifier, the three-element "Audion
Lee de Forest c. 1904
De Forest, some time between 1914 and 1922, with two of his Audions, a small 1-watt receiving tube (left), and a later 250-watt transmitting power tube (right), which he called an "oscillion".
American DeForest Wireless Telegraph Company's observation tower, 1904 Louisiana Purchase Exposition at Saint Louis, Missouri
Ohio Historical Marker: On July 18, 1907, Lee de Forest transmitted the first ship-to-shore messages that were sent by radiotelephone.
Vacuum tube
Videos
A vacuum tube, electron tube, thermionic valve, or tube is a device that controls electric current flow in a high vacuum between electrodes to which an electric potential difference has been applied.
Later thermionic vacuum tubes, mostly miniature style, some with top cap connections for higher voltages
Operating tubes in an audio power amplifier, the hot cathodes emitting their distinctive red-orange glow
Illustration representing a primitive triode vacuum tube and the polarities of the typical DC operating potentials. Not shown are the impedances (resistors or inductors) that would be included in series with the C and B voltage sources.
US WWV radio station signal generator using vacuum tubes, 1943