Car alarm Car alarm A car alarm is an electronic device installed in a vehicle in an attempt to discourage theft of the vehicle itself, its contents, or both. Car alarms work by emitting high-volume sound (often a vehicle-mounted siren, klaxon, pre-recorded verbal warning, the vehicle's own horn, or a combination of these) when the conditions necessary for triggering it are met. Such alarms may also cause the vehicle's headlights to flash, may notify the car's owner of the incident via a paging system, and may interrupt one or more electrical circuits necessary for the car to start. Although inexpensive to acquire
Horn light 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