10baseT Wiring Procedures

Termination with RJ-45 modular connectors

Currently, most campus computers with ethernet access are hooked up via Unshielded Twisted Pair 10baseT wiring. Generally, this cabling will contain 4 pairs. However, the ethernet currently only uses 2 of those 4 pairs. So in some cases, either a 2-pair is used for each connection, or one 4-pair is used for two separate ethernet connections. RJ-45 modular connectors are used to terminate the cables. Below are the proper orders for the individual wires in a 4-pair 10baseT (left) and a 2-pair 10baseT (right) when terminated with an RJ-45. It should be noted that the 2 active pairs in the left-hand illustration below are the orange and green (pins 1, 2, 3, and 6).

        Straight                Cross
        PIN     Signal          PIN     Signal
        1       TX+             3       RX+
        2       TX-             6       RX-
        3       RX+             1       TX+
        4       -               4       -
        5       -               5       -
        6       RX-             2       TX-
        7       -               7       -
        8       -               8       -