There are several types of cables used widely in pro audio - mic cables and patch cords with 2 or 3 conductors, instrument cables with 2 conductors, basic speaker cables with 2 conductors and MIDI cables comprised of DIN5 connectors using 2 conductors. The CableCOP features a full selection of standard pro audio connectors for testing all such cables. LEDs on the CableCOP link its various connector terminals and will only illuminate when the connected "cable" completes a circuit. As a result you are able to tell, at a glance, which cables need to be repaired. Sometimes the problem can be the cable itself. An LED may also fail to illuminate if a 3-conductor cable has been wired out-of-phase. As an example, if the Tip of one 1 / 4" TRS plug on a (balanced) patch cable were soldered to the same cable conductor as the Ring or Sleeve of the other 1 / 4" TRS plug. Specifications: Power Requirements 9V Battery (included) Dimensions 3.75x2.5x1.5 inches (90mm x 63mm x 40mm) Weight 1lb (454g)