With Wire tester you can check LAN patch cable (RJ45) and telephone cable (RJ11) for pass, open, short or cross wire. You can quickly test cables using scan mode, or step mode to check connection one contact at a time. Detachable remote unit allows you to test wires already installed. Pop a 9-Volt battery(Not Included) in and you're ready to test the connection to any room in your home or office. Warning This cable tester cannot test any electrified product. Test cannot be done while RJ45 copper screezers are not totally pressed. Any disobey leads to a permanant damage of the ends Please use quality tools to press the cables. Any end not notified by RJ11 cannot test telephone cable. Any disobey leads to a permanant damage of the ends