![]() ![]() Both electrodes alternate between acting as an anode and a cathode when these devices run with alternating current.Ī cold cathode is distinguished from a hot cathode that is heated to induce thermionic emission of electrons. Any gas-discharge lamp has a positive (anode) and a negative electrode. These lamps are commonly used for neon signs. The term "neon lamp" refers to tubing that is smaller than 15 mm in diameter and typically operates at approximately 40 milliamperes. This larger-diameter tubing is often used for interior alcove and general lighting. In the lighting industry, “cold cathode” historically refers to luminous tubing larger than 20 mm in diameter and operating on a current of 120 to 240 milliamperes. ![]() Neon lamps primarily rely on excitation of gas molecules to emit light CCFLs use a discharge in mercury vapor to develop ultraviolet light, which in turn causes a fluorescent coating on the inside of the lamp to emit visible light.Ĭold-cathode fluorescent lamps were used for backlighting of LCDs, for example computer monitors and television screens. 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.Ĭold-cathode lamps include cold-cathode fluorescent lamps (CCFLs) and neon lamps. Counter tubes were used widely before development of integrated circuit counter devices. 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. A Dekatron is a cold-cathode tube with multiple electrodes that is used for counting. 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. Many types of cold-cathode switching tube were developed, including various types of thyratron, the krytron, cold-cathode displays ( Nixie tube) and others. 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. Neon lamps are used both to produce light as indicators and for special-purpose illumination, and also as circuit elements displaying negative resistance. Study of the phenomena in these devices led to the discovery of the electron. Early cold-cathode devices included the Geissler tube and Plucker tube, and early cathode-ray tubes. The stacked digit arrangement in a Nixie tube is visible hereĪ cold-cathode vacuum tube does not rely on external heating of an electrode to provide thermionic emission of electrons. ![]()
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