Editing Cold cathode (section)

{{Short description|Type of electrode and part of cold cathode fluorescent lamp}}
{{About|light sources and indicators|cold cathode ion sources|Ion source}}
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[[File:Gase-in-Entladungsroehren.jpg|thumb|right|A set of cold cathode discharge tubes]]
A '''cold cathode'''<ref>{{US Patent|1993187}}, Cold cathode discharge tube</ref> is a [[cathode]] that is not electrically heated by a [[Electrical filament|filament]].<ref group="note">A negatively charged [[electrode]] emits [[electron]]s or is the positively charged terminal. For more, see [[field emission]].</ref> A cathode may be considered "cold" if it emits more electrons than can be supplied by [[thermionic emission]] alone. It is used in [[Gas discharge lamp|gas-discharge lamps]], such as [[neon lamp]]s, [[discharge tube]]s, and some types of [[vacuum tube]]. The other type of cathode is a [[hot cathode]], which is heated by electric current passing through a [[Electrical filament|filament]]. 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.