TIA-568A

TIA-568A is a wiring standard used by 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 cables. The pairs have the primary colors of blue, orange, green, and brown. They normally have the secondary color white.

Wiring

In TIA-568A, modular jack pins are numbered 1 through 8 from left to right, looking down from the top. The side with the tab that locks it into the socket being the bottom. 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 straddling the 1st (white/blue), the 3rd (white/green) pair on the left, 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.......G/W 1.......O/W G/W 2.......G 2.......O G 3.......O/W 3.......G/W O/W 4.......Bl 4.......Bl Bl 5.......Bl/W 5.......Bl/W Bl/W 6.......O 6.......G O 7.......Br/W 7.......Br/W Br/W 8.......Br 8.......Br Br 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 abovementioned backwards compatibility.

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

See also

• TIA-568B

  External links

• UTP Cable Termination Standards 568A Vs 568B