Spoiler warn: there's no universal ‘finest metal detector for gold’. (Although the GPZ 7000 is shut for those of you who can afford a detector that’s the exact same selling price as a car or truck). The 2 principal coils are connected to an oscillator that generates a radio frequency. https://factory.activeboard.com/t72455658/gold-detector-chronicles-of-treasure-hunts/?page=last#lastPostAnchor