Be prepared for a MASSIVE amount of signal splatter.
You will hear it through walls and sometimes a few feet away from the actual location of the cable. The gain/amplification in signal is in factors of 10s.
It's saved me many times, but at the same time, once you've narrowed it down to a couple of cables, it may pay to go back to the normal way, just to make sure you're definitely on the right pair.
Problems worthy of attack, prove their worth, by hitting back. -Piet Hein.
