Kidde i4618 Firex Hardwire Ionization Smoke Detector with Battery Backup (4 Pack) Red LED flashes until reset for quick, clear identification of initiating smoke alarm in interconnected system Visible low battery indicator helps locate chirping unit Front loading battery door makes battery changing simple, power link tab makes installation faster False alarm control quiets unwanted alarms for up to 8 minutes Interconnects with other compatible Firex smoke alarms and heat alarms