Neon lamp

The lamp typically consists of a small glass capsule that contains a mixture of neon and other gases at a low pressure and two electrodes (an anode and a cathode).

The characteristic, brilliant red color that is emitted by gaseous neon when excited electrically was noted immediately; Travers later wrote, "the blaze of crimson light from the tube told its own story and was a sight to dwell upon and never forget.

[4] A Smithsonian Institution website notes, "These small, low power devices use a physical principle called coronal discharge.

[5] Glow lamps found practical use as indicators in instrument panels and in many home appliances until the widespread commercialization of light-emitting diodes (LEDs) in the 1970s.

Convective currents make the glowing areas flow upwards, not unlike the discharge in a Jacob's ladder.

A photoionization effect can also be observed here, as the electrode area covered by the glow discharge can be increased by shining light at the lamp.

[9] The precise values of starting and maintaining voltages of neon lamps is subject to change due to several effects.

One measure to mitigate for this effect is to include a pilot lamp within the enclosure to provide an initial source of light.

Lamps intended for use as circuit components may be specially processed to eliminate most of the initial aging effects.

These attributes make neon lamps (with series resistors) a convenient low-cost voltage tester.

The breakdown characteristic of glow-discharge lamps allows them to be used as voltage regulators or overvoltage protection devices.

Neon lamps were used to make relaxation oscillator circuits, using this mechanism, sometimes referred to as the Pearson–Anson effect[14][16][17] for low frequency applications such as flashing warning lights, stroboscopes[18] tone generators in electronic organs,[14] and as time bases and deflection oscillators in early cathode ray oscilloscopes.

Neon lamps have been historically used as microwave and millimeter-wave detectors ("plasma diodes" or glow discharge detectors (GDDs)) up to about 100 GHz or so and in such service were said to exhibit comparable sensitivity (of the order of a few 10s to perhaps 100 microvolts) to the familiar 1N23-type catwhisker-contacted silicon diodes[citation needed] once ubiquitous in microwave equipment.

More recently it has been found that these lamps work well as detectors even at sub-millimeter ("terahertz") frequencies and they have been successfully used as pixels in several experimental imaging arrays at these wavelengths.

Since at least the 1940s, argon, neon, and phosphored glow thyratron latching indicators (which would light up upon an impulse on their starter electrode and extinguish only after their anode voltage was cut) were available for example as self-displaying shift registers in large-format, crawling-text dot-matrix displays,[24] or, combined in a 4×4, four-color phosphored-thyratron matrix, as a stackable 625-color RGBA pixel for large video graphics arrays.

[27][28] Because of their comparatively short response time, in the early development of television neon lamps were used as the light source in many mechanical-scan TV displays.

Novelty glow lamps with shaped electrodes (such as flowers and leaves), often coated with phosphors, have been made for artistic purposes.

Ultraviolet radiation then can be used to excite a phosphor coating inside of the bulb and provide a wide range of various colors, including white.