Electromechanical horns and bells are classic forms of audible signalling equipment. As their name suggests, they generate signals mechanically.
Distinctive signal tone and a timeless design.
In the case of the horn, the magnetic force of a coil moves a clapper, which strikes a metallic membrane at a frequency of 100 to 150 Hz, generating the typical low-frequency, easily recognisable horn tone.
In the case of the bell, a clapper strikes a bell dome and creates the typical, distinctive bell tone that cannot be reproduced electronically with the same level of sound quality.