Monoprice RJ-11 and RJ-45 Modular Plug Tester (108138) 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 And Can Be Stored In The Included, Zippered, Synthetic Leather Case The Master And Remote Unit Each Have A Series Of 9 Led That Show The Status Of Each Line On The Attached Cable The Tester Supports Both A Fast Automatic And A Slow Automatic Mode