100BaseT4
The advantage to 100BaseT4 is its capability to use older categories of UTP cable to perform 100Mbps transfer. In environments already wired with Category 3 or 4 cable, 100BaseT4 can be used instead of replacing the existing cable.
100BaseT4 uses all four pairs of wire of Category 3, 4, and 5 twisted pair and, as such, is prevented from using full-duplex transmissions. The other characteristics of standard 100BaseTX are in effect with 100BaseT4.