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 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. 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