568A Versus 568B Cables

There are two different standards released by the EIA/TIA group about UTP Wiring568A and 568B. Although 568B is newer, and is the recommended standard, either one can be used. The difference between these two standards is pin assignments, not in the use of the different colors. The 568A standard is more compatible with voice connections and the Universal Service Order Codes (USOC) standard for telephone infrastructure in the USA. In both 568A and USOC standards, the blue and orange pairs are now on the center four pins; therefore, the colors match more closely with 568A than with the 568B standard.

So which one is preferred? Information here from the standards bodies on this matter is sketchy at best. 568B was traditionally widespread in the USA, whereas places like Canada and Australia use a lot of 568A. However, 568A is now becoming more dominant in the USA as well.

Tip:

Use 568A in new installations, and 568B if connecting to an existing 568B system.

568A Standard				568B Standard
Pin	Color	Pair	Description	Pin	Color	Pair	Description
1	white/green	3	RecvData +	1	white/orange	2	TxData +
2	green	3	RecvData -	2	orange	2	TxData -
3	white/orange	2	Txdata +	3	white/green	3	RecvData +
4	blue	1	Unused	4	blue	1	Unused
5	white/blue	1	Unused	5	white/blue	1	Unused
6	orange	2	TxData -	6	green	3	RecvData -
7	white/brown	4	Unused	7	white/brown	4	Unused
8	brown	4	Unused	8	brown	4	Unused

Tip:

Odd pin numbers are always the striped wires.

A straight-through cable is one with both ends using the same standard (A or B).

A crossover cable is one that has 568A on one end, and 568B on the other end.