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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 10BASE-T and 100BASE-TX. It is also used by many digital telephone PBX systems.

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

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 orange pair on the left, the brown pair on the right, the blue pair (reversed) in the center, and the green pair straddling the blue.

Because the blue pair is the first pair, this provides simple backwards compatibility with older uses of RJ-45 and RJ-11 plugs 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 white).

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

Note that since no function is defined for the blue and brown pairs in 10 or 100BASE-T, that the blue and brown pairs may or may not be swapped.

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

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