First Alert - BRK SA302LCN Lithium 9V Battery Powered Dual Sensors, Photoelectric and Ionization Sensors Smoke Alarm with Two Silence Features and Intelligent Sensing Technology 9V Lithium Battery operated Photo/Ion dual smoke sensor alarm. Utilizes both ionization and photoelectric smoke sensors for maximum protection Single button test/silence - Intelligent Sensing TechnologyTM helps reduce the number of nuisance alarms Remote Control Silence/Test uses most remote controls to temporarily quiet unwanted alarms and test alarm functions Two silence features - can silence the low-battery chirp for up to eight hours or temporarily silence an unwanted nuisance alarm