TIA/EIA 568 A vs. B

Ricky · 2022-11-05T01:21:59+00:00

I was looking up the wiring diagrams for Ethernet cables and found TIA/EIA 568A and TIA/EIA 568B wiring diagrams. They seem to be wired the same, but for the colors used. They swap green and orange. At first I thought I was looking at a crossover cable, but no, they clearly say they should be connected the same at each end. One uses orange and green pairs, while the other uses green and orange pairs for half the signals. This reminds me of the Star Trek episode where the Black/White guy was fighting the White/Black guy. Anyone know what's going on with TIA/EIA 568 A vs. B?

Nov 05, 2022 Last reply: 3 years ago 27 Replies

Rate this thread:

Cydrome Leader 3 years ago

This is mostly true. The amount of twist is different between the colors. There's two amounts of twist used, strip the sheath off a cable and look at the pairs. It's obvious once you see it. Wiring up patch cables with odd color sequences may not meet specs.

I use 568B for panels as that's what AT&T/lucent/Avaya/whoeverit is now ones silkscreen right on the front.

Commercially made patch cables will almost always be 568B.

Stop buying junk cables. Panduit 688 series plugs have been the best for decades. They don't snag and they don't break apart.

Vote

Ricky 3 years ago

The reference I found said there were four twists used, and also indicated the amount of twist is not in the standard. So no point in assuming any correlation between twist and color.

They don't seem to indicate that, but I'll never know, even if I buy them. I suppose I could use a lens and look at the connectors carefully. I think they are mostly clear.

Vote

Lasse Langwadt Christensen 3 years ago

each pair have a different number of twists per length to reduce crosstalk

Vote

John Walliker 3 years ago

According to para 5.8.2 of TIA 568.C.2 "Because of their identical pair groupings, patch cords terminated in either T568A or T568B may be used interchangeably, provided that both ends are terminated with the same pin/pair scheme." As for the number of twists per unit length, the standard simply states: "5.6.2 Pair assembly The pair twist lengths shall be chosen to ensure compliance with the transmission requirements of this Standard." In other words, it is entirely up to the cable manufacturer to choose how many twists per unit length are used so long as the completed cable is within specification. So different patch cables could have totally different internal construction and still meet the standard.

John

Vote

Ricky 3 years ago

Yes, different from one another and each an unknown quantity. So no point in preserving any wiring scheme thinking the specific twist associated with a color is significant.

Vote

Ricky 3 years ago

Bingo! Give the man a kewpie doll!

Vote

Join the Discussion

Have something to add? Share your thoughts — no account required.

Didn't find your answer?

Ask the community — no account required