Kidde Smoke & Carbon Monoxide Detector, Hardwired with Lithium Battery Backup, Voice Warning, model i12010SCO, is a hardwired combination smoke and CO detector with a sealed-in lithium battery backup. The combination smoke & carbon monoxide alarm provides reliable detection of smoke & dangerous CO gas, even during power outages. Using both ionization & electrochemical sensor technology, the hardwired smoke detector senses invisible fire particles quickly and senses dangerous CO. Because carbon monoxide is present in all fires, having a combination smoke and carbon monoxide detector with battery backup in one unit allows both sensors to work together to help protect your family. By communicating constantly, the alarm can adjust its sensitivity to better discriminate between an actual hazard and a false one, significantly reducing the potential for nuisance, or “false” alarms.Two LEDs keep you informed about the alarm's status, while a voice warning will verbally announce "FIRE" or "WARNING! CARBON MONOXIDE.” A red LED will flash in unison with the alarm pattern to warn of fire, carbon monoxide, and low battery. The green LED will remain steady to indicate AC power and flash every 60 seconds when in battery-only mode. This Kidde hardwired combination smoke and CO detector with battery backup can be connected with other Kidde alarms in your home to help protect your family. A maximum of 24 Kidde devices can be interconnected in a multiple station arrangement but cannot exceed the NFPA (National Fire Protection Association) limit of 18 initiation devices, of which 12 can be smoke alarms. With 18 initiating devices (smoke, heat, CO, etc.), interconnected, it is still possible to interconnect 6 strobe lights and or relay modules. UL Certified with a 10-year limited warranty. Meets requirements of UL 2034, UL217, NFPA72, The State of California Fire Marshal, NFPA 101, FHA, & HUD.