When you need these things, you need them. Used - as shown, no docs.This cable tracker allows you to identify and trace wires and cable without piercing or damaging insulation. The tracker is designed to hunt down telephone lines, alarm cables computer cables, intercom lines and more for short and open circuits. The cable tracker and its accessories come organized in a handy carrying case.Identify and trace electrical wires or cables without damaging insulationChecks for short circuits and open circuitsDesigned for use with telephone lines, alarm cables, computer cables, intercom lines, speaker wires, and thermostat wiring