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