kenotron

He is known for inventing the first thermionic valve or vacuum tube, the diode, then called the kenotron in 1904.

However, because Pliotron and Kenotron were registered trademarks, technical writers tended to use the more generic term "vacuum tube".

It was also called a thermionic valve, vacuum diode, kenotron, thermionic tube, or Fleming valve.

Vacuum rectifiers were made for very high voltages, such as the high voltage power supply for the cathode ray tube of television receivers, and the kenotron used for power supply in X-ray equipment.