Horn light
"Horn light" is the term used in American and Canadian fire alarm systems to describe the annunciators used to notify the occupants of a building that an alarm condition exists and at least that area of the building should be promptly evacuated. The device emits a very loud noise and also uses a xenon strobe light to call attention to itself.
Older horn lights were "unsupervised". These devices, when powered by a direct current voltage, simply sounded and flashed for as long as the voltage was present. Newer horn lights are supervised; these can separately annunciate and flash so that they can be silenced while still providing the visual notification that occupants should evacuate the area.
Fire safety codes generally call for all separately enclosed areas to contain at least one horn light so that the annunciation is obvious even in enclosed spaces such as conference rooms and toilet rooms.
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