Cold Cathode

A cold cathode is a cathode, an electrode that emits electrons, which is not electrically heated by a filament. They are used in gas discharge lamps such as neon lamps, discharge tubes, and some types of vacuum tube. The other type of cathode is a hot cathode, which is heated by a filament which has electric current passing through it. A cold cathode does not necessarily operate at a low temperature; it is often heated to its operating temperature by other methods, such as the current passing from the cathode into the gas.