... ,precious stones,ores,zinc,Chrome,copper,etc 2.superior quality TX-MPI Mine Locator Natural Electric Auto Frequency SelectorGold Detector Natural ... natural electric field, through special amplify method it just need 20 meters receiver pole to complete survey. 2 people is enough ... 't be lost when power off. 5 It can storage 20 curve measuring data of3 frequency and 30 frequency.6 Curve ...