Any of the locators work the same way. A small map will appear in a box at the top right corner. A red square will appear on the map depending on the type of locator you use.
Though there seems to be a bug on this item, its still pretty useful for navigation as well as locating mines.
The Bug - The map at the top will not show anything except for the box's border when you go too deep (?) inside the caves.
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