Keep your network running smoothly by testing your cables to uncover problematic shorts, open wires, crossing pairs and other wiring mishaps for testing your Ethernet cables to make they are in working order prior to connecting to your devices Tests RJ45 cables, RJ11 cables and network cables Easy to read LED display indicates problems.Hand- for portability. Requires one 9-volt battery (not included) Following are abnormal connections: If one cable, for example cable NO.3 is open circuited, the two NO.3 lights of the main tester and remote tester will not turn on. If cables are not connected, lights will not turn on respectively. If less than two cables are connected, none of the lights is on. If two ends of a cable is disordered, for example NO. 2and NO. 4, then displays on: Main tester: -4-5-6-7-8-G Remote tester: 1-4-3-2-5-6-7-8-G If two cables are short circuited, neither of the corresponding lights is on of the remote tester while main tester remains unchanged. If three cables, including three, are short circuited, none of the corresponding lights is on. If test panels or wall plate outlles, two cables which can match each other (RJ45) will be connected to the tester. If test cables of the axes, BNC turns on when the cable works. 9V reduplicated battery is used in this tester. Battery is advised to change if any weak light appears.( Battery is not included.) Material:PC+ metal colour:Black + white Package Contents: 1 * Network Cable Tester Only the above package content, other products are not included. Note: Light and different displays may the color of the item in the a little different from the real thing. The measurement allowed error is +/- 1-3cm.