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