page_title: Cold cathode
section_title: Cold-cathode devices
hierarchical_section_title: Cold cathode / Cold-cathode devices
caption_attribution_description: Deutsch: Eine leuchtende Nixie-Röhre (Telefunken ZM1210 mit entferntem Tauchlack und gekürzten Lötfahnen). Durchmesser: 19&#8201;mm; Ziffernhöhe: 15,5&#8201;mm. Das Drahtgitter vor den Ziffern ist Teil der Anode. Die Röhre selbst enthält insgesamt elf Kathoden, wovon zehn für die Darstellung der Ziffern 0&#8201;&#8211;&#8201;9 und eine (unten links) für den Dezimalpunkt verwendet werden. English: Nixie tube Telefunken ZM1210 (without coating) operating. Diameter: 19mm, digits' height: 15,5mm. The filament in front of the digits is part of the anode. The tube has eleven cathodes: ten of them formed as the digits 0 to 9 and one (in the lower left) as decimal point. Français&#160;: Un Tube Nixie Telefunken ZM1210 (nu) en fonctionnement. Diamètre: 19 mm, taille des chiffres, 15,5 mm. Le filament devant les chiffres fait partie de l'anode. Ce tube contient 11 cathodes: Une par chiffre, plus le point décimal. This is a retouched picture, which means that it has been digitally altered from its original version. Modifications: perspective correction. Modifications made by Richard Bartz.
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: A cold-cathode vacuum tube does not rely on external heating of an electrode to provide thermionic emission of electrons. Early cold-cathode devices included the Geissler tube and Plucker tube, and early cathode ray tubes.  Study of the phenomena in these devices led to the discovery of the electron.
  Neon lamps are used both to produce light as indicators and for special-purpose illumination, and also as circuit elements displaying negative resistance. Addition of a trigger electrode to a device allowed the glow discharge to be initiated by an external control circuit; Bell Laboratories developed a "trigger tube" cold-cathode device in 1936.
  Many types of cold-cathode switching tube were developed, including various types of thyratron, the krytron, cold-cathode displays (Nixie tube) and others. Voltage regulator tubes rely on the relatively constant voltage of a glow discharge over a range of current and were used to stabilize power-supply voltages in tube-based instruments. A Dekatron is a cold-cathode tube with multiple electrodes that is used for counting.  Each time a pulse is applied to a control electrode, a glow discharge moves to a step electrode; by providing ten electrodes in each tube and cascading the tubes, a counter system can be developed and the count observed by the position of the glow discharges. Counter tubes were used widely before development of integrated circuit counter devices.
  The flash tube is a cold-cathode device filled with xenon gas, used to produce an intense short pulse of light for photography or to act as a stroboscope to examine the motion of moving parts.
caption: The stacked digit arrangement in a Nixie tube is visible here
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