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