???? ??????? ??????? ?? ?? ??? ???? ????? ????? ?? ???????? ???????? ?????? ??????. ????? ?? ???? ?????? ????? ???? ?????? ?? ???? ????? ????? ?? ?????.The very first steel detector was very likely The easy electric conduction steel detector ca. 1830.[41] Electrical conduction was also used to locate metal ore bodies by measuring the conductivity a