Southwire's M300P Professional VDV Low Voltage Cable Mapper Tool Kit is perfect for testing voice; data; and video cabling for common wiring faults including split pairs. The cable mapper features an easy-to-read LCD display with backlight and port covers that protect the RJ45 and RJ11 ports from dust and debris. The cable mapper easily maps multiple cable runs with included RJ45 and COAX ""F"" ID remotes. The rugged durable molded housing with snap-in remote is impact resistant for long lasting performance and use. TESTING TIP: If you receive a “U” when testing a cable then it indicates an unidentifiable error. This typically is a result of multiple wiring errors on one particular cable. Typically this is resolved by terminating the ends again." TESTING TIP: If you receive a “U” when testing a cable then it indicates an unidentifiable error. This typically is a result of multiple wiring errors on one particular cable. Typically this is resolved by terminating the ends again