The PG21 door alarm series from Alarm Lock are a quick and inexpensive solution when faced with security vulnerabilities from doors being propped open in schools, restaurants, nursing homes and theaters. Whether door-propping occurs for quick returns from taking "smoke" breaks, to permit insider-jobs or to allow unregistered visitors or contraband to circumvent main security entry points, it remains a problem for facility managers and security officers everywhere. These surface-mount, narrow stile, microprocessor controlled door alarms quickly improve security at any single or double door with a 95dB alarm, entry delay (15 seconds, 1 min. 15 sec., and 3 mins 15 sec. options), key-removal and auto-shutdown/reset options. The PG21 has two selectable arming modes, always armed mode (when key is turned counter clockwise to the disarm position, the key cannot be removed, to remove key, turn back to arm mode, thus keeping unit armed always) and standard mode (when key is inserted turning counter clockwise will disarm and key can be removed, turning key clockwise will arm and key can be removed). Can be used for multiple door monitoring with built-in external reed switch. Unauthorized use of door causes the 95db alarm to sound and activates LED indicator as well as the highly visible, flashing amber strobe (available on some units). Uses standard mortise cylinder, not included.