Applications
Most small neon (indicator-sized) lamps, such as the common NE-2, break down at between 90 and 110 volts. This feature enables their use as very simple voltage regulators or overvoltage protection devices. In the 1960s General Electric (GE), Signalite, and other firms made special extra-stable neon lamps for electronic uses. They even devised digital logic circuits, binary memories, and frequency dividers using neon lamps. Such circuits appeared in electronic organs of the 1950s, as well as some instrumentation. At least some of these lamps had a glow concentrated into a small spot on the cathode, which made them unsuited to use as indicators. These were sometimes called "circuit-component" lamps, the other variety being indicators. A variant of the NE-2 type lamp, the NE-77, had three parallel wires (in a plane) instead of the usual two. It was also intended primarily to be a circuit component.
Small neon lamps are used as indicators in electronic equipment. Called "tuneons" in 1930s radio sets, they were fitted as tuning indicators, and would give a brighter glow as the station was tuned in correctly. Larger lamps are used in neon signage. Neon lamps, due to their low current consumption, are used as nightlights. Because of their comparatively fast response time, in the early development of television neon lamps were used as the light source in many mechanical-scan TV displays. They were also used for a variety of other purposes; since a neon lamp can act as a relaxation oscillator with an added resistor and capacitor, it can be used as a simple flashing lamp or audio oscillator. (See Pearson-Anson effect.)
Neon lamps with several shaped electrodes were used as alphanumerical displays known as Nixie tubes. These have since been replaced by other display devices such as light emitting diodes, vacuum fluorescent displays, and liquid crystal displays. Novelty glow lamps with shaped electrodes (such as flowers and leaves), often coated with phosphors, have been made for artistic purposes. In some of these, the glow that surrounds an electrode is part of the design.
In AC-excited lamps, both electrodes produce light, but in a DC-excited lamp, only the negative electrode glows. Thus a neon lamp can be used to distinguish between AC and DC sources and to ascertain the polarity of DC sources.
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