This simple tester allows faults in ISDN and Ethernet cables using RJ45 connectors to be traced quickly and efficiently.Many Ethernet and ISDN connection systems employ sockets and plugs called ‘RJ45’. They look like a slightly wider version of the RJ11 or ‘Western’ connectors as found on modern telephone sets. The RJ45 connector has 8 pins, although in some cases only four or six are actually used (designation: RJ45-4/8 and RJ45-6/8 respectively). The connectors are available in screened and nonscreened versions. For 10 Mbit/s and 100 Mbit/s (as well as for ISDN), the unscreened variants of the plug/socket combination is sufficient, provided the cables are of the ‘twisted pair’ type (unshielded twisted pair, UTP).