This option uses two pairs of category 5 UTP or two shielded twisted-pair (STP) cable to connect a station to hub as shown in Fig. One pair is used to carry frames from the hub to the station and other to carry frames from station to hub. It uses 4B/5B encoding to handle 100 Mbps using NRZ-I signalling. The distance between station and hub should be less than 100 meters.

                 Figure ; 100Base-TX implementation

100 BASE FX:

This option uses two Fiber optic cables, one carry frames from station to hub and other from hub to station as shown in Fig. The encoding is using 4B/5B and it uses NRZI signalling. The distance between station and hub should be less than 2000 meters.

                 Figure ; 100Base-FX implementation