It is basically magnetometer, really. Good one, meanwhile. Allow you to detect rotating magnets and wires with AC current anywhere and measure their strength. Main purpose - finding wiring in the walls to not drill al hole through it. Working frequency is 30-300Hz so it is purposed for the 50/60Hz mains power cables.

It is basically magnetometer, really. Good one, meanwhile. Allow you to detect magnets anywhere and measure their strength.