Alarm sounder / bell

Offshore F&G layout practice (ISA 5.1-style letter codes) / ISO 7240 / NFPA 72 / IEC 60617 (bell, sounder)

Drawn as

A half-circle dome sitting on a flat base line (the IEC bell or sounder), with its connection below.

Meaning

Electronic sounder or bell for fire, gas and general alarm. Usually paired with a beacon; becomes alarm-beacon (beacon and sounder). Large-area PA/GA horns are the loudspeaker symbol.

Variants

Horn symbols (a trumpet shape) are also used for sounders