This device is used to test the line 
For the proper cabling, breakdown, short circuit and pair polarity
- Test RJ45 (UTP/STP), RJ12, RJ12(DEC), RJ11, RJ9, and BNC cables
 - Additional spare battery & two 6P to 4P adapters included in the remote box
 - Identifies open, shorted, crossed, revered and transposed wires.
 - Maximum cable length: 1000 ft.
 - Power: DC 9V battery
 - Includes a black leatherette carrying case
 
Warning: Not to be used on live circuits