RJ45 and RJ11 Network Cable Tester is used to check if there's wiring issues in Ethernet and telephone cables. It is specifically used to tests for open circuits, short circuits, and crossed pairs in straight-through or crossover wiring types. It requires a single 9V PP3 battery to operate, which is typically not included with the tester.It has a LED display to detect quickly if troubleshoot and verify the continuity of twisted-pair cables like CAT5, CAT5e, or CAT6.