This is a green, surface-mounted emergency break-glass call point typically used in access control and fire alarm systems to facilitate quick evacuations. [1, 2]
It features a manual override mechanism where breaking the glass (or activating a resettable plastic lens) instantly cuts power to connected electric locks. [1, 2]
The unit is constructed from fireproof material with a sandblast finish and is often rated IP65 to resist dust and moisture. [1]
It is a fail-safe device that can be reset using a dedicated key after activation.