When triggered, all smoke detectors in your house alarm concurrently. Tough-wired detectors are usually on and when the power goes out, the battery backup kicks in.?????? ???? ???? ???? ????? ????? ?? ????? ?? ??????? ??? ???? ????? ???????? ?????? ?? ??????? ??????? ???? ???? ????? ???????? ?? ??? ??? ???????? ??????? ?????? ???????? ?? ?????? ???