First Alert OLCOV SmartBridge Wireless Interconnected Carbon Monoxide Alarm with Voice and Location NA Wireless interconnect, battery operated carbon monoxide alarm - when one alarm sounds, they all sound Electrochemical CO sensing technology for best accuracy Audible 85dB alarm also includes voice function that announces the location of the CO hazard Features easy silence/test button, low battery warning, front-load battery drawer and 10 Year Warranty Also compatible with SmartBridgeTM DIY Home Automation system (gateway required and is sold separately)