Vehicle horn horn. Bicycles often have a classic "bulb horn", operated by squeezing a rubber bulb attached to a metal horn. Squeezing the bulb forces air through a steel reed located in the throat of the horn, making it vibrate, producing a single note. The flaring horn matches the acoustic impedance of the reed to the open air, radiating the sound waves efficiently, making the sound louder. Other types of horns used on bicycles include battery-operated horns (sometimes even car horns on 12-volt circuits are incorporated) and small air horns powered by a small can of compressed gas. Oliver Lucas of Birmingham,
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