Sound activated. Responds to fire alarms, releasing the door in the event of a fire. Wire-free, for easy retrofitting to any door. Intelligent release feature can be programmed to react to a particular fire alarm sound, significantly reducing false activations. Easy to install and has adjustable closing speeds. Includes an LED display, manual release button and a low battery warning display. Ideally suited to environments where it is essential to have doors in an open position at certain times of the day to aid access, but equally important to ensure the doors are closed in the event of a fire. Advanced Acoustic Digital Technology Battery-Powered Holding Angle: 65-105° Size 4 Daily Timed Release Option Low Battery Indicator Digital Display Adjustable 2 Year Guarantee Free Swing Mode Option Advanced Acoustic Digital Technology Battery-Powered Holding Angle: 65-105° Size 4 Daily Timed Release Option Low Battery Indicator Digital Display Adjustable 2 Year Guarantee Free Swing Mode Option