4 ternary plus (4T+)

4T+ is a special line coding to transmit Fast Ethernet over simple telephone cabling.

At the end of the 1980s, this specified 4T+ coding had the advantage that Fast Ethernet could be transmitted over simple category 3 telephone cables without having to lay a new cabling infrastructure with TP cables of a higher category. The classic telephone cables were laid in all buildings and offices.

The 4T+ method uses CSMA/ CD as the access method, using four category 3 UTP cables. The method used in 100Base-T4 uses three pairs of cables each for data transmission and the fourth pair for collision detection. The 8B6T coding is used in this procedure.