The SDC 491 "Break Glass" Emergency Door Release provides immediate unlocking of perimeter doors or interior doors that are equipped with fail-safe electric locks. The 491s siren may be used as a local door annunciator. The SDC 491 is specifically designed for emergency door release and may influence the approval of an electric locking system. This type of Emergency Door Release may be preferred over a pull station since greater commitment is required to break the glass. Also known as -Sdc - Security Door Controls BREAK GLASS RELEAS W/ SIREN - SZ-491
