Within the 1960s, the main industrial steel detectors were generated, they usually have been commonly useful for mineral prospecting and various industrial applications.(?? ???? ?????? ??? ??? ???? ????? ????? ??? ?????? ????) ???? ??? ?? ????? ????? ????? ????? ???? ???????? “????? ???? ?????? ?? ??????? ??? ????? ????? ?? ?????? ???? ???? ??? ?