Sorry about the blurry camera. This is a 120 volt Faraday klaxon horn, probably dating from the 1930's-40's. These were widely used as warning signals in public buildings, factories, military installations, secret evil lairs, and particularly on Navy ships. Short-belled versions were used as dive alarms on submarines.
In a vibratory alarm horn, an electromagnet vibrates against a diaphragm to create a buzzing sound. In a klaxon, a motor turns a toothed wheel or gear which presses against a stud mounted on the diaphragm. As the gear turns, it's teeth move the stud and diaphragm forward and backward, making the classic "aooogah" sound.
Southpark: I only answer questions written in whole words.
Audinos 3 weeks ago