Vehicle horn England, developed a standard electric car horn in 1910. Car horns are usually electric, driven by a flat circular steel diaphragm that has an electromagnet acting on it in one direction and a spring pulling in the opposite direction. The diaphragm is attached to contact points that repeatedly interrupt the current to that electromagnet causing the diaphragm to spring back the other way, which complete the circuit again. This arrangement opens and closes the circuit hundreds of times per second which creates a loud noise like a buzzer or electric bell, which sound enters a horn to be amplified. There
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