TIA-568B Guide, Meaning , Facts, Information and Description

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 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

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 10/100Base-T crossover cable, the 2nd and 3rd pairs are swapped on one end:

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

   ______________________________
   |   |  |  |  |  |  |  |  |   |
   |   8  7  6  5  4  3  2  1   |
   |                            |
   |______  Front of plug ______|
         |____        ____|
             |________|

  Normal pin configuration:      10/100BASE-T Crossover configuration:

               Both Ends                       End 1   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    W/Br
       5.......W/Bl                    5.......W/Bl    Br/W
       6.......G/W                     6.......G/W     O/W
       7.......W/Br                    7.......W/Br    Bl/W
       8.......Br/W                    8.......Br/W    W/Bl

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

See also

• TIA-568A

• UTP Cable Termination Standards 568A Vs 568B

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