Ethernet over twisted pair

Early Ethernet used various grades of coaxial cable, but in 1984, StarLAN showed the potential of simple unshielded twisted pair.

10BASE-T1S is a direct competitor of CAN XL in the automotive space and includes a PHY-Level Collision Avoidance scheme (PLCA).

[11] The StarLAN 10 signaling was used as the basis of 10BASE-T, with the addition of link beat to quickly indicate connection status.

[c] Using twisted-pair cabling in a star topology addressed several weaknesses of the previous Ethernet standards: Although 10BASE-T is rarely used as a normal-operation signaling rate today, it is still in wide use with network interface controllers in wake-on-LAN power-down mode and for special, low-power, low-bandwidth applications.

Where there are several standards for the same transmission speed, they are distinguished by a letter or digit following the T, such as TX or T4, referring to the encoding method and number of lanes.

An infrastructure node (such as a hub or a switch) normally uses the complementary wiring arrangement, called MDI-X, the X standing for -crossover.

Later equipment often can automatically switch between MDI and MDI-X arrangements as needed, obviating crossover cables and manual selection, but in the conventional arrangement, when two nodes having the same (fixed) type of port need to be connected, a crossover cable is required.

[14] A 10BASE-T transmitter sends two differential voltages, +2.5 V or −2.5 V. A 100BASE-TX transmitter sends three differential voltages, +1 V, 0 V, or −1 V.[15] Unlike earlier Ethernet standards using broadband and coaxial cable, such as 10BASE5 (thicknet) and 10BASE2 (thinnet), 10BASE-T does not specify the exact type of wiring to be used but instead specifies certain characteristics that a cable must meet.

The spare pairs may be used for power over Ethernet (PoE), for two plain old telephone service (POTS) lines, or for a second 10BASE-T or 100BASE-TX connection.

[25] In June 2023, 802.3cy added 25 Gb/s speeds at lengths up to 11 m.[26] Similar to PoE, Power over Data Lines (PoDL) can provide up to 50 W to a device.

[29][30] Higher speed standards, 2.5GBASE-T up to 40GBASE-T[31] running at 2.5 to 40 Gbit/s, consequently define only full-duplex point-to-point links which are generally connected by network switches, and do not support the traditional shared-medium CSMA/CD operation.

exist for Ethernet over twisted pair, and most network adapters are capable of different modes of operation.