When brought on, all smoke detectors in your home alarm simultaneously. Challenging-wired detectors are usually on and when the facility goes out, the battery backup kicks in.?????? ???? ???? ???? ????? ????? ?? ????? ?? ??????? ??? ???? ????? ???????? ?????? ?? ??????? ??????? ???? ???? ????? ???????? ?? ??? ??? ???????? ??????? ?????? ???????? ??