First Alert BRK 10-Year Battery 6-Pack Hardwired Combination Smoke and Carbon Monoxide Detector120V AC DC Interconnectable Ionization Smoke & CO Alarm w 10 YR Locked Battery Backup (6 Pack) Precision Detection technology helps reduce cooking nuisance alarms and provides early warning. Interconnects with most First Alert and BRK alarms so when one sounds, all compatible alarms sound to provide an early warning Latching Alarm Indicator visually identifies the unit that initiated the alarm or low battery warning 10 Year battery backup provides