Kidde 21007583 Firex Wire-In Smoke Alarm With Battery Backup, 85 DB At 10 FT Loud, 60 HZ Operating Frequency, 120 VAC Operating, 80 MILAMP Operating, 40 - 100 DEG F Operating, Environmental Conditions: Up To 85 PCT Relative Humidity (RH), Ionization Sensor, Dimensions: 5.6 IN Diameter X 1.8 IN Depth