TIA-568B

EIA/TIA-568B is a joint Electronic Industries Alliance (EIA), Telecommunications Industry Association (TIA), and International Telecommunications Union (ITU) standard for twisted pair wiring. It defines the pinout, or order of connections, for wires in RJ-45 8-pin modular connector plugs and jacks.

TIA-568B is the wiring standard used by most modern computer LAN media on twisted pair wire, such as Ethernet 10BASE-T and 100BASE-TX. It is also used by many digital telephone PBX systems.

Colors

It defines the 8 wires in four pairs, matching AT&T standard color codes as also found in 25-pair color codes. The pairs have the primary colors of blue, orange, green, and brown. They normally have the secondary color white.

Wiring

A standard cable is used to connect a Network interface card (NIC) in a computer to a hub. A crossover cable may be used to directly link two computers together.

In TIA-568B, modular jack pins are numbered 1 through 8 from left to right, looking down from the top. The color order on these pins would be:

In other words, this gives the 1st (white/blue) pair reversed in the center, the 2nd (white/orange) pair on the left, the 3rd (white/green) pair straddling the 1st (white/blue) pair, and the 4th (white/brown) pair on the right.

Crossover wiring

In 10Base-T/100Base-TX crossover cable, the 2nd and 3rd pairs are swapped on one end: <--fixme: add info on 100base-T4 crossover cable and if it exists 1000baseTX crossover-->

Backwards compatibility

Because the blue pair is the first pair, this provides simple backwards compatibility with uses of RJ-11, RJ-14, RJ-25 and RJ-61 wiring with the first pair in the center.

Sometimes the second wire in the pair is manufactured as a solid color instead of having dots of the secondary color (normally solid white for the first five pairs in the 25 pair color code).

Diagram

T568-B T568-B 10/100Base-T Straight-Through 10/100BASE-T Crossover configuration: configuration: Both Ends Plug End 1 Plug End 2 1.......W/O 1.......W/O W/G 2.......O/W 2.......O/W G/W 3.......W/G 3.......W/G W/O 4.......Bl/W 4.......Bl/W Bl/W 5.......W/Bl 5.......W/Bl W/Bl 6.......G/W 6.......G/W O/W 7.......W/Br 7.......W/Br W/Br 8.......Br/W 8.......Br/W Br/W Note that since no function is defined for the 1st (white/blue) and 4th (white/brown) pairs in 10 or 100BASE-T, that those pairs may or may not be swapped, or may not be even present at all, however swapping or removing them would break the above mentioned backwards compatibility.

(Color key: Bl = Blue, O = Orange, G = Green, , Br = Brown)

See also

• TIA-568A

  External links

• UTP Cable Termination Standards 568A Vs 568B
• proAV / data and information, lists, tables and links
• Ethernet Cable Colour code standards