I love my tone tracer! It even works with wires inside Bergmann conduit (Orangeburg pipe with a thin outer coating of sheet metal, not earthed) in plastered brick walls. I only have a rather inexpensive one, 85 Euros. Allowed me to spot a buried splice +/- 1 cm! Some moron moved a door (and light switch) by just splicing new wires to the old cloth-covered ones and plastering over the old switch box. I found the splice, patched in a new section of flex conduit instead of the box, pulled new wires through the now complete conduit run and that was it.
