Cable Tester is requisite and needful in network installation and maintenance. Cable Tester for RJ-11, RJ-12, RJ-45, CAT5, CAT5e, 10/100BaseT, TIA-568A/568B, AT&T 258-A.RJ45 Network Cable Tester test correspondingly double-twisted cables 1, 2, 3, 4, 5, 6, 7, 8 and Ground, 9 LED lights to indicate wiring connection on both remote and master unit. With this Network Cable Tester, you can judge wrong connection, short circuit and open circuit.