page_title: Cold cathode
section_title: Applications
hierarchical_section_title: Cold cathode / Applications
caption_attribution_description: English: A photo of an illuminated compact fluorescent lamp (CFL) of the cold cathode variety. The spiraled tube is thinner and longer than the tube on a standard (hot cathode) CFL. This bulb is rated at 8 watts and 350 lumens.
context_page_description: A cold cathode is a cathode that is not electrically heated by a filament. 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 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 electric current passing through a 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.
context_section_description: Cold cathodes are used in cold-cathode rectifiers, such as the crossatron and mercury-arc valves, and cold-cathode amplifiers, such as in automatic message accounting and other pseudospark switching applications. Other examples include the thyratron, krytron, sprytron, and ignitron tubes.
  A common cold-cathode application is in neon signs and other locations where the ambient temperature is likely to drop well below freezing, The Clock Tower, Palace of Westminster (Big Ben) uses cold-cathode lighting behind the clock faces where continual striking and failure to strike in cold weather would be undesirable. Large cold-cathode fluorescent lamps (CCFLs) have been produced in the past and are still used today when shaped, long-life linear light sources are required. As of 2011, miniature CCFLs were extensively used as backlights for computer and television liquid-crystal displays. CCFL lifespans vary in LCD televisions depending on transient voltage surges and temperature levels in usage environments.
  Due to its efficiency, CCFL technology has expanded into room lighting. Costs are similar to those of traditional fluorescent lighting, but with several advantages: the light emitted is easier on the eyes, bulbs turn on instantly to full output and are also dimmable.
caption: An illuminated cold-cathode CFL
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