EXHIBITS > The automatics of Heron >
The sound alarm
It was a sound device that was activated by the opening of the door that it protected. It consisted of a trumpet adapted to a concave hemispherical container that was suspended from an articulated bar. With the opening of the door, a rope allowed the inclination of the bar and consequently the descent of the trumpet. The hemispherical container was sunk into a container with water and the enclosed air in this forced the trumpet to sound.
SOURCES: "Heron of Alexandria, Pneumatica, (17)"