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