This Monoprice RJ11/RJ45 tester is a simple yet powerful tool that helps troubleshoot network and telephone cables for broken wires and crossed connections.The tester consists of a main Master unit and a detachable Remote unit each of which have an RJ11 and an RJ45 jack. The unit is powered with a 9-volt battery (not included) and can be stored in the included zippered synthetic leather case.The Master and Remote unit each have a series of 9 LEDs that show the status of each line on the attached cable. The tester supports both a fast automatic and a slow automatic mode.