Cable Tester: 1.Test RJ11/RJ12/RJ45 cables. 2.Test correspondingly double-twisted cables 1, 2, 3, 4, 5, 6, 7, 8 and Ground. 3.Can judge wrong connection, short circuit and open circuit. 4.Put cables into both main tester and remote tester. 5.The lights of the main tester will turn on sequentially from 1 to G. 6.Detachable remote tester, test remote cable up to 1,000ft. in length. 7.Power supply: 2 pcs AAA batteries (not included).