100base-T wiring specifies an 8 position jack two pair. These are pairs two and three of AT&T and TIA schemes.

The USOC wiring scheme hass four versions supporting 1, 2, 3, and 4 pair systems. Pair one is on the two center contacts, pair two is on the next two contactrs and so forth.

Token Ring usually uses an 8 position jack. The wiring schemes is compatible with TIA, AT&T and USOC wiring schemes because it uses the two center pairs

EIA/AT&T T568 has adopted the TIA and AT&T wiring schems. They are similar, but pair two and three are reversed. The TIA scheme is popular because it is compatible with one or two pair USOC systems. Both schemes will support ISDN application