It says that the trace is pretty usless over 15ft. Like Bishop said, the fluke kit gets some really good reviews for finding breaks along the cable runs and can even detect shorts and give you the distance to the short (i.e. if a nail goes through one).
We're using one here. It even displays the length of the cable. It also maps the connections of your 8-wired RJ-45 connector so can see the wires numbered 1-8 how is it connected to the other end.
