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#165512 - 06/29/07 05:02 AM 568A or 568B ????
CTBigman Offline
Junior Member

Registered: 09/11/06
Posts: 2
Loc: Connecticut
We use the Leviton Quickports for Data/Phone/CATV and follow the government standard of TIA-568-A. We also install network jacks and patch panels for small businesses. Several times we have been told by the computer installers or the IT people that we should be using 568-B, that 568-A does not work and we end up rewiring the jacks. (now we ask 1st) Which is correct/better????

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#165518 - 06/29/07 08:39 AM Re: 568A or 568B ???? [Re: CTBigman]
EV607797 Offline
Member

Registered: 10/25/06
Posts: 756
Loc: Fredericksburg, VA, USA
First, TIA is NOT a government standard or rule. No one can force you to follow their standards. EIA/TIA standards are a suggested practice set forth by a private organization.

568A and B are electrically the same. It's just a matter of reversing the pin positions for the white/orange and white/green pairs. As long as both ends are wired the same way, nobody will ever know which standard was used.
_________________________
---Ed---

"But the guy at Home Depot said it would work."

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#165551 - 06/29/07 08:22 PM Re: 568A or 568B ???? [Re: CTBigman]
e57 Offline
Member

Registered: 05/27/03
Posts: 2837
Loc: S.F.,CA USA
First don't confuse the Standard with the pinout terminations... There is a TIA/EIA 568-A, and later a B. But there is also a T568A and B that refer to the terminations. There are some that will say that they are electricaly different. (I'm not one of them) However, you'll find that TIA/EIA 568B is the current standard since Cat5e, and Cat6 were released. And that many spec's will be written to require "B" as a standard...

Although these standards are widely used, there are relitively few people who actually own them. (As they cost an arm and a leg) But some manufacturers have truncated overviews of the content in easy language. Apparently the "B" standard doesn't actually say to use "B" pinouts and leaves it as a choice. But prefers the "A" pinouts.....
Anixter

You'll note that 568-A is not listed, as it is considered antiquated as a standard by many. As B is technicaly the most current standard. (Which actually says that you can use the "A" pin-outs!!!!) And then there are people who feel the same about "B" pinouts, as written by a guy one one of my favorite phone sites.
http://www.ablecables.com.au/568avb.htm#_Toc426467840

Wiki currently has a nice artical on it:
http://en.wikipedia.org/wiki/TIA/EIA-568-B

Bottom line is to keep same with same in existing situations, and/or follow the spec's for the job. But they both have to be the same one both ends - no two cooks in the kitchen... Or it then will not work....


_________________________
Mark Heller
"Well - I oughta....." -Jackie Gleason

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#165552 - 06/29/07 08:39 PM Re: 568A or 568B ???? [Re: e57]
e57 Offline
Member

Registered: 05/27/03
Posts: 2837
Loc: S.F.,CA USA
Oh- The people who say it is electrically different in terms of transmision say that because the orange pair (Which is twisted more than the others) stays twisted right up to the punch down in a jack better in the B configuration than in the A configuration where they would be split and claim that it results in less NEXT and FEXT.... In my mind, if you're looking that close - you have other problems on your network other than wiring...
_________________________
Mark Heller
"Well - I oughta....." -Jackie Gleason

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#165573 - 06/30/07 02:49 PM Re: 568A or 568B ???? [Re: e57]
Trumpy Offline

Member

Registered: 07/05/02
Posts: 8540
Loc: SI,New Zealand
Mark,
Thanks for the above links.
I've found these two standards confusing in the past, not that I do a lot of data work, but it is handy to know what the two standards actually mean.
_________________________
Let's face it, these days if you're not young, you're old - Red Green grin

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#165580 - 06/30/07 05:09 PM Re: 568A or 568B ???? [Re: Trumpy]
gfretwell Offline

Member

Registered: 07/20/04
Posts: 9045
Loc: Estero,Fl,usa
The color of the wire doesn't really make much difference in NeXT if the Ethernet port is still using pin 3 and 6, which they do.
If they were really concerned they would not use these 2. This is left over from a standard Ma Bell came up with in the first RJ14 and got rid of the 4 round pin plug. At audio frequencies it works great.
There are some styles of keystones that deal with this better than others. The ones with the punch downs opposing each other in 2 rows seem to work pretty well on the TDR.
_________________________
Greg Fretwell

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#165590 - 06/30/07 10:26 PM Re: 568A or 568B ???? [Re: gfretwell]
EV607797 Offline
Member

Registered: 10/25/06
Posts: 756
Loc: Fredericksburg, VA, USA
We are talking about the use of the white/orange and white/green pairs. These are also the transmit and receive pairs. There is absolutely no way that reversing them by using the A or B wiring pattern can possibly have any operational effect. "If" the white/orange pair has a tighter twist length, then reversing it to other pin positions simply affects either the transmit or receive pair's carrying capacity.

Please, please, please disregard the use of the "RJ" terminology. This is an entirely separate industry; a set of FCC wiring patterns for voice circuits for telephone companies (utilities) to follow. The term "RJ45" is perhaps the most grossly-misused term in the entire industry. Trust me, what an RJ45 is and what people think it is are two very different things. It's just the computer geeks linking them because the jacks appeared to be similar that caused this debacle.

I can put an RJ14 wiring pattern on any of today's modular jacks, or I should say any jack manufactured since 1974, no matter how many pin positions that the jack holds.

We are only talking about pin positions, not the hardware itself. This is a HUGE misconception in the voice and data industry. You will likely never see a true "RJ45" jack and if you do encounter one that is still wired and working, please send me a photo, along with your name and address and I will send you a dollar.
_________________________
---Ed---

"But the guy at Home Depot said it would work."

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#165593 - 07/01/07 04:40 AM Re: 568A or 568B ???? [Re: EV607797]
iwire Offline
Moderator

Registered: 01/05/03
Posts: 4343
Loc: North Attleboro, MA USA
Ed it's a done deal RJ45 now 'means' something else then it really was.

You can fight it but I don't see it changing.

Mark thanks for the links as well.
_________________________
Bob Badger
Construction & Maintenance Electrician
Massachusetts

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#165601 - 07/01/07 07:59 AM Re: 568A or 568B ???? [Re: EV607797]
pauluk Offline
Member

Registered: 08/11/01
Posts: 7693
Loc: Norfolk, England
I too think that the arguments over whether the 568A or 568B wiring configuration is better are quite pointless. If the tighter twist patterns were going to make that much of a difference, we'd also better change the existing pin 3/6 pair over to pins 7/8 or something similar.

While we're around the twist..... ;\)

 Quote:
The people who say it is electrically different in terms of transmision say that because the orange pair (Which is twisted more than the others)


I've just examined the pairs on a length of Enhanced CAT5 UTP currently in my supplies and come up with the following figures for twists-per-foot:

White/blue = 32
White/orange = 19.5
White/green = 25.5
White/brown = 18

So on this cable the green pair is more tightly twisted than the orange anyhow.

As Ed says, even if this was a significant factor, swapping the positions of the W/O and W/G pairs is only going to swap the characteristics of the receive and transmit data paths anyway.

The reason for having different twist rates is to minimize crosstalk. If each pair had exactly the same twist, then where the pairs lie together in the cable you'd get places where tip of one pair is repeatedly next to tip of another pair, ring of one pair repeatedly next to ring of another pair and so on. The different twists mean that over any reasonable length of cable the coupling between any two individual conductors of different pairs in minimized.

If you are adding to an existing installation I think the most important thing is to be consistent and follow whatever method is already in use to avoid confusion. If starting from scratch, it really doesn't matter which you adopt, although personally I stick with 568B.

 Quote:
You will likely never see a true "RJ45" jack


I'd bet that there has never been a true RJ45 installed in this country! And isn't RJ45 a keyed 8-position connector anyway, not the "RJ45" of present-day network connections?

The RJ numbers are probably misused even more on this side of the Atlantic, since nobody has ever heard of USOC and certainly doesn't realize that they refer to the wiring configuration, not just the physical plug/jack style.

I had a query from somebody (non technical) the other day about hooking up a laptop in European hotel rooms. She said that several places she'd contacted had told her that they provided an RJ25 jack for visitors to plug in their modems. She'd never heard of RJ25.

I'd be willing to bet that the jack is really just RJ11, but somebody in the hotel(s) concerned did a quick internet search and decided that because that "weird-looking American jack" is 6 position that it must be RJ25.

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#165627 - 07/01/07 05:19 PM Re: 568A or 568B ???? [Re: pauluk]
e57 Offline
Member

Registered: 05/27/03
Posts: 2837
Loc: S.F.,CA USA
 Originally Posted By: pauluk
I've just examined the pairs on a length of Enhanced CAT5 UTP currently in my supplies and come up with the following figures for twists-per-foot:

White/blue = 32
White/orange = 19.5
White/green = 25.5
White/brown = 18


Funny..... I just looked at three differnt rolls of 5E and amount of twist on all in decending order most to least - Orange, blue, green, brown. HUH?????
_________________________
Mark Heller
"Well - I oughta....." -Jackie Gleason

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