First Alert OLCOMBOV Wireless Interconnected Photoelectric Smoke and Carbon Monoxide Alarm with Voice and Location RF wireless interconnect, battery operated alarm, when one alarm sounds, they all sound Audible 85dB alarm also includes voice function that announces the type and location of the smoke/fire/carbon monoxide hazard Includes electrochemical CO sensor for best accuracy and photoelectric smoke sensor to reduce nuisance alarms from cooking Features easy silence/test button, low battery warning, side-load battery drawer and end of life signal for easy replacement Meets UL standards and backed by 7 year limited warranty. RF wireless interconnect, battery operated alarm - when one alarm sounds, they all sound Audible 85dB alarm also includes voice function that announces the type and location of the smoke/fire/carbon monoxide hazard Includes electrochemical CO sensor for best accuracy and photoelectric smoke sensor to reduce nuisance alarms from cooking Features easy silence/test button, low battery warning, side-load battery drawer and end of life signal for easy replacement Meets UL standards and backed by 7 year limited warranty. NOTE: These flexible alarms can be used as wirelessly connected home alarms (purchase alarms only) or can be integrated into the SmartBridge DIY Home Automation system so you can received email or text notification in the event one of the alarms sound while you are not at home (requires purchase of SmartBridge Gateway sold separately).