(Russian, signal’nyipribor), a lighting device used to produce light signals, which may be steady or discrete in nature. Discrete, or flashing-light, signals may be coded.

The light sources employed in such devices are either continuously burning lamps—for example, incandescent or carbon arc lamps—or flash lamps. Devices with continuously burning lamps are used to produce steady or flashing signals; the frequency and color of the flashing signals may change or remain constant. Devices with flash lamps provide short, intense flashes, which constitute either independent pulses or series of pulses. In the case of devices using continuously burning lamps, flashing is produced by means of louvers and movable opaque screens or by turning the lamps on and off. When flash lamps are used, flashing is effected by the system that electrically fires the lamp and supplies it with power.

Devices for signaling in a specific direction are equipped with light-directing optical systems. Sometimes signal lights are provided with color filters. Infrared filters are used to transmit signals invisible to the eye.

The uses of signal lights include the transmission of coded information—for example, navigation and military signals—and the indication of an object’s position or direction of motion—as in transportation systems. High-power devices, such as beacons and searchlights (whose signals may be, for example, in Morse code), consume about 10⁴ watts (W) of power and provide approximately 10⁴–10⁵ joules (J) of energy in a flash. Medium-power signal lights consume about 10³ W and provide 10²–10³ J; examples of such devices are airfield lights, running lights of ships, traffic signals, and railroad signals. Low-power devices consume about 10² W and provide up to 10² J; such lights include signal lanterns and signal lights on aircraft, spacecraft, ships, motor vehicles, and channel buoys.