SC9120B - 120V AC/DC Smoke/CO Combo Alarm - Hardwired ionization/CO combination alarm meets new construction requirements. 10 year CO Sensor/10 year End of Life. Electrochemical Carbon Monoxide Sensor - the most accurate sensor available as compared to other sensing technologies. 9V Alkaline Battery Backup. Latching alarm indicator - remembers which unit initiated an alarm. Two silence features - can silence the low-battery chirp for up to eight hours or temporarily silence an unwanted nuisance alarm. End of Life Signal provides audible notification alarms needs to be replaced. Intelligent Sensing TechnologyTM helps reduce the number of nuisance alarms. Perfect Mount - allows for easy alignment of alarm. Dust Cover. Easy Installation/Maintenance - Preferred features include a large opening in the mounting bracket for easy access to wiring. Keyhole slots in the mounting bracket eliminate the need to remove the electrical box screws for installation. A battery pull tab keeps the battery fresh until the home is occupied. Battery installation and removal can occur while the unit is mounted to the ceiling or wall via the side load battery compartment. Two locking features are provided to prevent battery theft and/or theft of the unit. Connection to AC power is made with a "Quick-Connect" wiring harness. Installation is quick, easy and cost effective. Single button test/silence. 10-Years Limited Warranty.