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#603232 08/20/16 11:36 PM
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What is 568a used for? I believe Niles audio equipment at one time required this config. Can you mix 568a and b cables on same network, as long s each cable testsgood?

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srd1 #603234 08/21/16 12:48 AM
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Mixing is a "no". 568A is TIA/EIA configuration. 568B is an AT&T (Western Electric) configuration.

Which to use is either personal preference or what was used on an existing installation.

Personally, I use 568B.


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srd1 #603235 08/21/16 01:53 AM
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You can do your own research as to why there are two configurations. It's easy enough to find. In general, 568A is used in government offices, and 568B everywhere else. Thus, most people use B.

Although, the last govt cabling job I had this summer specified B. (State govt.).

Jim


srd1 #603244 08/21/16 04:11 PM
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OK. Soapbox rant time (with apologies to Ed).

Once upon a time (back in the '80s) there was no standard for Data cabling. To quote the Bible when they talk about evil times: "Every man did what was right in his own eyes."

We had Ethernet (Thick and thin coax), we had Starlan, we had IBM type I, II & III, we had twinax, we had dual coax, we had asynchronous networking over serial cables and modem eliminators, we had.....everything!

For cabling installers it was heaven!

Somene would move into a new office and we would rip out what was there and install new wiring. A firm would hire a new DP (Data Processing) chief and we would rip out everything and put in his favorite flavor. It was wonderful!

In the mid-to-late '80s the EIA (Electronics Industry Association) and the TIA (Telecommunications Industry Association) got together with cabling and equipment manufacturers and decided to create standards for all aspects of networking. One of the first standards they created was the wiring standard. It was the 568 (no letter) standard. It was equivalent to todays "A" wiring.

Then AT&T popped up and bitched. They had a very similar wiring standard that they used in their Dimension series PBXs. They had thousands of people trained in it and....they were AT&T.

To make a long rant somewhat shorter they insisted that if the industry did not adopt THEIR standard, then they would not participate. Well no one wanted the '800 lb. gorilla' to be on the outside of the tent pissing in, so they brought them in to the tent by agreeing that there could be two standards - "A" or the original standard and "B", the alternate standard that followed the AT&T wiring plan.

When I teach the IBEW apprentices about Data wiring and termination I tell them that when they show up on the job, the first question they have to ask is "A or B?". If their foreman looks at them blankly they should prepare for a disaster and the prospect of much overtime.

And as far as the disaster everyone in the industry foresaw (We'll never wire another office again! Who would ever need anything more then 100mbs Cat5?). Hah! Cat5E, Cat 6, Cat 6A and coming soon - Cat7!

I now return the soapbox to Ed.

Sam


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srd1 #603245 08/21/16 05:39 PM
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Beautiful, love the history! Most likely, none of the techs that we work with would know that.

Though, we have a situation that the existing cables are mixed, some A, some B. everything worked fine for months. Now, we have problems. Have internet at modem, everytime we hook up modem to network, internet doesn't work.

Have feeling that a wrong device is plugged into an Ethernet port somewhere in house.

Or can it be, out of the blue, the mixed configs, are causing this, when they weren't before.

All cables test out fine.

srd1 #603249 08/21/16 05:51 PM
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Most AT&T jobs that I have followed and used the existing wiring scheme were A not B. The green and orange pairs were transposed. Now this was Merlin installs that I converted to two pair back in the day when I was installing a lot of Vodavi two pair systems. Normally the phone would connect to blue/orange pairs, but using AT&T wiring it would connect to blue/green at the mdf. The B standard was AT&Ts data wiring plan, but when it came to phones they stuck with the A, which screwed up their own techs when they installed Spirit systems.

Wiring diagram 568 a and b

Last edited by Derrick; 08/21/16 05:55 PM.

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srd1 #603250 08/21/16 07:11 PM
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Quote
Or can it be, out of the blue, the mixed configs, are causing this, when they weren't before.

All cables test out fine.

As long as BOTH ENDS of a cable are wired the same (either A or B) there will be no problem. The signal doesn't care what color the pairs are since the difference between the two schemes just swaps the orange and green pairs. You would have a problem when one end is A and the other B. But since you say the cables test fine then that is not an issue.

As Sam says it's important to know and maintain the standard used in a facility. The only problem mixing both standards will cause is the difficulties techs will have trying to figure out what was used where when it comes time to change things.

-Hal



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srd1 #603252 08/21/16 08:43 PM
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A CG that I work a lot with/for told me at the very beginning that if the cables test fine, then walk away as it was the CG's or IT's problem.

Makes my job a lot easier. smile


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Years ago, we installed an Inter-Tel Axxess for a rather large tech company. They did their own wiring and insisted that voice be put on patch panels.

Tried to convince them to run all Cat 5 (at the time) so any jack could be used for voice or data, since they were using patch panels. Nope, they used Cat 3 for voice.

The guy wiring the patch panels wired them as B, because "everyone knows that patch panels are B". The guy doing the jacks wired them as A, because "everyone knows that voice is A".

Since the Axxess system used pins 3 and 6, none of the phones came up. Fortunately, the guy doing the jacks left enough slack to rewire them. About a hundred of them, if I remember correctly.

srd1 #603398 08/26/16 01:37 AM
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If you are in the server domain environment, you might have issues on the server side with gateway settings, service etc... If there is a domain involved, try rebooting the server, make sure that server is up and running, all of the required services are running and configured properly.

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