Don Heany would like this, and we all should know about it.

Toner instruction is usually to connect the two wires from the tone generator to a wire pair. This results in a usually very clean tone signal that you can pick up at the other end of a hundred foot long wire (or any place along the way). But the nature of wire pairs is that their construction tends to cancel them out.

So a MUCH stronger signal can be put on the wire by grounding one output of the tone generator -- either output, red or black -- and connecting the other one to one of the wire conductor. I've traced wires in an attic from the room below over a distance of sixty feet using this method, where I was waving the wand above my head and the wires put out a signal great enough to be picked up by the wand.

If the wire is in a conduit, or the wire conductor you choose is grounded, this method is pretty much useless.