When brought on, all smoke detectors in your home alarm concurrently. Difficult-wired detectors are generally on and when the ability goes out, the battery backup kicks in.????? ????? ??????? ?????????? ????? ??? ?? ??? ????? ????? ????? ?? ??????? ??????? ??? ?????? ?...???? ?????? ??????? ?? ???? ????? ??? ??????? ? ????? ??? ????? .????? ???????