Easily traces wires in walls, ceilings and floors! This thing works, but to trace wires in walls you have to turn down the signal from the transmitter and the sensitivity of the receiver. In my new house, a chain of outlets was unplugged, I was able to trace the wire to the source of the problem. I had to trace the wires because after unplugging all the outlets to see if a wire was disconnected I was at a loss. Turns out the last owner of the house decided to add an extra GFI along the way and decided to plug the original GFI back instead of to the side of the line to keep it from popping. Well it showed up but I didn't know because it still had the power. That way I could use a cable locator to trace the wires to the miswired GFI and hook everything up correctly. I've also used it to trace a severed piece of Romex from the junction box through the ceiling where I can't see where it went. The instructions are not a very good translation, but I think the tool is intuitive enough to use without it. It can also monitor live circuits, but the voltage readings will be about 10 volts lower than a regular multimeter on a 120 volt AC circuit. Maybe it's not designed to read AC, I don't know because the instructions aren't very clear. It is clear that it can be used in circuits up to 400 volts. But I am not an electrician and unless you are an electrician do not connect it to any live circuit.