Twisted-pair Ethernet

Ethernet over twisted pair technologies use twisted-pair cables for the physical layer of an Ethernet computer network.

Early Ethernet had used various grades of coaxial cable, but in 1984, StarLAN showed the potential of simple unshielded twisted pair. This led to the development of 10BASE-T and its successors 100BASE-TX and 1000BASE-T, supporting speeds of 10, 100 and 1,000 Mbit/s respectively.

All these standards use 8P8C connectors, and the cables from Cat3 to Cat8 have four pairs of wires; though 10BASE-T and 100BASE-TX only use two of the pairs.

The Institute of Electrical and Electronics Engineers (IEEE) standards association ratified several versions of the technology. The first two early designs were StarLAN, standardized in 1986, at one megabit per second, and LattisNet, developed in January 1987, at 10 megabit per second. Both were developed before the 10BASE-T standard (published in 1990 as IEEE 802.3i) and used different signalling, so they were not directly compatible with it.

In 1988 AT&T released StarLAN 10, named for working at 10 Mbit/s. The StarLAN 10 signalling was used as the basis of 10BASE-T, with the addition of "link beat" to quickly indicate connection status. (A number of network interface cards at the time could work with either StarLAN 10 or 10BASE-T, by switching link beat on or off.)

Using twisted pair cabling, in a star topology, for Ethernet addressed several weaknesses of the previous standards:

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