... , bank, library, computer house and storehouse etc.Stand alone Smoke Detector Main FeaturesHush functionAC power supply,9V back-up batteryTest button, HUSH ... Smoke Detector Technical Parameter Operating voltage,AC220V,with 9V back-up batteryTemperature Range,40°F to 100°F (4°C ... 2.06%/ftSound level,85dB/3 meters (10ft)Interconnects,Up to 40pcs smoke alarmHush function,YesDimension,Φ128*38mm AC ...