Vacuum tube diode |
 |
|
Before the development of doped semiconductor technology in the 1950's, radio, radar and TV etc. were operated with valves. The diode valve was the simplest. A hot wire heated a cathode coated with Cesium oxide. Thermal electrons crossed the space to an anode. Current was permitted in only one direction. Note: in teh 1960's transistors and integrated circuits replaced valve circuits in all but very high current, high frequency, situations (transmitters). Valve radios had wonderful tone. They can still be bought and are maintained by enthusiasts. |