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?

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.

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

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

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.

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

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

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.

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.

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.

OK, here I go. Take a deep breath, Ed:

Let's remember that AT&T's standard (which is now referred to as 568B or WECO) was developed in the early 1970s, before anyone else was a huge player with regard to system manufacture. Sure, there were other manufacturers, but none had the dedicated marketing power that AT&T had with their Bell companies in nearly every major city. (Sorry for the side-track).

AT&T needed an 8P8C solution to support their MET sets (Modular Electronic Telephone) on Dimension and Horizon PBXs, so they developed it on their own. They later transitioned this standard to their Merlin key telephone systems in the early 80s. This wiring was never intended to support anything but their own proprietary telephone systems and it had absolutely nothing to do with computer networks. Voice was on pair one (pins 4/5), data was on pins 3/6 and power was on pins 1/2. This was done to prevent any harm by someone plugging a standard phone cord into a MET jack since no pins in the plug would engage with both power pins, which were effectively out of reach for a standard 6P4C plug. Pretty smart, huh?

As Sam said, the computer networks at this time were on everything from COAX to TwinAX to you name it.

THEN came a problem with the divestiture of the Bell System in 1984. The Universal Service Order Code (USOC) was developed so that a customer could order a jack from any local telco using a standard 'RJ' designation. From Miami to Seattle and all points in between, you would be guaranteed to receive the same jack wired the way it was ordered. RJ11 for one line, RJ14 for two, RJ25 for three and RJ61 for four.

USOC jacks were wired from the center two pins outward, meaning that line one was on the center two pins, line two was on the next pins outward from center, line three was on the next two outward pins, and so on. It was fairly simple.

At some point, Ethernet wiring for computer networks transitioned over from COAX to 50-ohm unshielded twisted pairs, and in the early days, CAT3 cable was more than sufficient to support 10 Mbps transmission speeds. Only two pairs are needed for Ethernet over twisted pair (transmit and receive). How does the industry adapt to the obvious need for a modular jack that can be convenient for the user, yet ensure that nothing will blow up if they plug into the incorrect jack?

There is when the problem arose. Stick with existing USOC wiring patterns could potentially put CO line voltages at 48 volts or more on pins of a jack that are meant for data connections. They built in a safeguard under the USOC program where all of the tips on lines 2,3 and 4 were to left of center and the rings were to the right. This meant that anything plugged into a USOC jack wouldn't be harmed under the emerging Ethernet or the existing AT&T (later 568B) standard. Man, they sure had to put a lot of thought into this process, didn't they?

I'm guessing that at this point, they had to figure out the least-dangerous pins to use if a computer got plugged into an RJ61X jack. Someone selected pins 1,2,3 and 6 as AT&T had previoiusly used them for their power and data connections on pins that were typically out-of-bounds.

So then came the issue of merging USOC, Ethernet and AT&T wiring standards on the same 8P8C jack. Seriously, some equipment damage can happen if someone plugs into the wrong jack. At first, the solution was keyed plugs and jacks. Data cables and jacks had a slot/tab on the left side that prevented the cables from being inserted into a voice jack that didn't have this keyway. That worked for a little while, but even that wasn't the solution.

Well, sort of. Earlier in the development of the USOC program, they already addressed this by mandating keyed jacks/plugs for telco data circuits that were often wired as RJ41S or RJ45S. The telco would put in a jack to terminate a data circuit, intending for it to be used for a modem with a keyed plug. This kept people from getting into trouble until twisted pair Ethernet came along in the late 80s. An unkeyed voice or Ethernet cable could still be plugged into a keyed USOC RJ41 or RJ45 telco jack.

So, back to the original subject: USOC was the national standard that telcos used, with pair one on pins 4/5, pair two on pins 3/6 and so on. Since there are hundreds of telcos in North America, many independent of AT&T, they had no knowledge of AT&T's own wiring standard on an 8P8C jack, so they maintained and standardized with today's 568A standard (remember the tips on the left thing I mentioned with the RJ61X configuration earlier).

At the end of the day, AT&T and it's Bell System companies maintained their standard and they weren't being told to change by anyone. At the same time, the independent (non-Bell) telcos were sticking with USOC standards. Something had to be done to bridge this gap. There was no changing the USOC standard; that was mandated by the FCC. AT&T stuck with what is now 568B and the independents went with their own 568A.

Truth is, 568A and B are exactly the same if they're wired using the same pattern at each end of the cable. It's only when a cable is terminated with A on one end and B at the other end where there will be a problem. As long as a site is wired using a uniform standard, nobody will notice a thing.

The answer to the original question is that the 568A and 568B standards were created as a result of two very powerful bodies refusing to change. Their refusal to change didn't net anything at all. Both systems work excactly the same.

Oh, and as for that RJ41/RJ45 reference made earlier: Those no longer exist. Telcos now deliver circuits on RJ48 jacks. CGs have stolen the RJ45 nomenclature to any network jack. I guess that's OK. My doctor told me to quit stressing about it.

SNET was considered an ILEC. Does that mean that they used 568A while their surrounding neighbors all used 568B (NYT & NET)

258a and 568b are the same...when was that designation changed?

Ed, as always, you're a treasure chest of knowledge...

Had to put in a little Vertical SBX today and to save time I made up a cable to save time on site. Uses standard 4p crimp on modular plugs and used pins 4&5. Well, I plugged it in, crossconnected, phone dead.Tested my rj14, tested good.After a bit of head scratching and since I didnt have ant documentation, I called tech support. Turns out, they use pins 3&6 for digital phones and 4&5 are analog. New one on me but I dont install much new stuff anymore.

568B is a wiring pattern. 258A is the part number for a six-port 'harmonica' type adapter that uses the 568B wiring pattern.

The Avaya Partner uses that same wiring format. Pins 4 & 5 are analog voice & ringing while pins 3 & 6 are used for digital signals between system phones and the various station modules.

I just assumed and we all know what happens when you assume.

From Flukes site:

T568A and T568B are the two color codes used for wiring eight-position RJ45 modular plugs.

Both are allowed under the ANSI/TIA-568-C wiring standards. The only difference between the two color codes is that the orange and green pairs are interchanged. T568A wiring pattern is recognized as the preferred wiring pattern for this standard because it provides backward compatibility to both one pair and two pair USOC wiring schemes. The T568B standard matches the older AT&T 258A color code and is/was (?) the most widely used wiring scheme. It is also permitted by the ANSI/TIA-568-C standard, but it provides only a single pair backward compatibility to the USOC wiring scheme. The U.S. Government requires the use of the preferred T568A standard for wiring done under federal contracts.


Really?

If you buy an ethernet patch cable, it always has the 568-B wiring pattern on both ends. If you buy an ethernet crossover cable, it has the 568-A wiring pattern on one end and the 568-B wiring pattern on the other end.

I have never seen a structured cabling installation for data that didn't use the 568-B wiring pattern. Cabling that was installed for an Avaya Merlin, Legend, Partner or similar phone system typically uses the 568-A wiring pattern.

There is a subtle difference between the two wiring patterns that makes little or no practical difference. The four twisted cable pairs in a standard Cat 5 cable each has a different twist rate. So they are of slightly different lengths. The more twists per inch, the longer the actual conductor. Isn't that right, ED?

Well maybe, but CAT5 wasn't even invented yet when those standards were developed. I believe CAT3 was the latest and greatest of the day. I believe there was a CAT1 and 2 but those predated the 568 standards.

-Hal

Cat 1 was the old JKT, 4 conductor (unpaired) station cable, known as "Quad". Four individual conductors, Green Red, Black and Yellow.

Cat 2 was like Cat 3 - Paired telephone cable, but with an almost negligible twist to the wires. When you opened the jacket the pairs practically fell apart into individual conductors. We used to instruct the young'uns to rip open the jacket and before removing it, tape the end of the cable. Then they would remove the jacket . Otherwise it might be too difficult to identify the actual pairs, especially in a high count cable.

Sam

I remember having CAT2 many, many years ago. When CAT3 came out I felt about it like I do CAT6 today.

-Hal

Oh, you're REALLY going to like Cat 7. Gag Here

Rcaman

-Hal

CAT7 is much better known in Europe than it is in the US. My question is...at what point does switching from copper to fiber become a no brainer for premise cabling

Looking at that, fiber has to be cheaper and easier.

-Hal

Devil's advocate here

We all know the colour code - blue, orange, green, brown,,, Let's terminate a four pair cable on an 8P/8C jack using 568B. The other end, being voice is terminated on BIX,, (or R66 blocks if you must ). Customer is using multi-line analog phones. Line one connects to blue pair, line two connects to green pair, line three connects to orange,, wait what? What happened to the colour code? Would that not make 568A the proper configuration?


We did a cabling job for a customer, who did not specify how he wanted things terminated. Finished the job using 568A and their "IT professional" made us come back and reterminate the whole project B because "none of my computers work. I have B patch cords and you cannot mix them." He then proceeded to Google network wiring standards while he was lecturing me. Just smiled and nodded, reterminated everything, and sent them a bill.


Also, the previous comment about "buy any patch cord and it will be 568B" is not accurate. I have a stack here from StarTech, Belden and various others including generic no name and they are probably a 50/50 split of A and B.

No. It would be USOC.

-Hal

Congratulations on having a client willing to pay you for fixing an "error" as they perceive it. I have trouble getting paid for work that was done right the first time.

I am a little confused about what you are saying. As long as you keep each phone line and each leg of an Ethernet connection on a single twisted pair, it should work. If you have split pairs, then you may have signal attenuation problems. Also if you did cross over the orange and green pair, most modern equipment will auto-sense that and still make the connection. So why wouldn't the computers work?

I have never seen a computer patch cable that was wired 568A at both ends, but it would still work. I would suspect that such a cable is not a computer patch cable but a telephone line cord which is not made with twisted pairs. These may not work with computers.

I had an install in a hotel a few years back for a franchise that required two line phones in every room. The electrical contractor terminated all the in room wiring on 8P/8C jacks using 568B. Connecting the second line, we had to connect the jumpers onto the green pair (typically line three). Yes, USOC is needed if using three or four line analog phones or you would be splitting the pairs.


Auto sensing network equipment doesn't do anything with a cable run terminated A with a B patch cord (or vice versa) Use a cable tester and and test from an A patch cord to a cable run terminated A and a B patch cable at the remote end, it will show as a straight thru cable run. Now remove the B patch cord and replace with a crossover cable (one end A, other end B) and you'll see the orange and green pairs flipped - this is where the auto-sensing kicks in. Before auto-sensing, had to use cross over cables when connecting switch to switch, etc.

Computers will work on two pairs if needed. They only use pins 1, 2, 3 and 6. Now granted, it's not ideal and will definitely fail any cable test and not recommended but have done it in situations where there is one cable run and customer wants a phone and computer and running a second cable is not an option.

I don't specifically order A or B patch cords, I order the length and colour I need and use whatever I receive. Trust me, the A patch cords are computer patch cords - Cat 5E and Cat 6 rated.

"Looking at that, fiber has to be cheaper and easier."

-Hal
====================================================

Fiber is cheaper - the electronics are not.

Prices for fibre network cards and switches are astronomical (at least the last time I looked).

Sam

I have never in my life seen a prefabricated computer patch cord that was terminated on both ends with 568A. If I bought such a cord, I would return it because whoever made it did not know what they were doing, in my opinion.

You also need to check the markings on the outside of the cable to make sure it is of the appropriate construction. If it is not stranded and marked for IEEE category (3, 5x or 6x) and UL type (CM, CMR, CMP etc.) return it. Unless you like to work overtime for free diagnosing unexplained problems.

Everybody is talking about CAT7 here in the states and it doesn't even exist here as TIA skipped the CAT 7 designation. CAT 7 is an ISO standard that is also called Class F.

I just don't get it as to why people don't understand that there are two standard bodies. The TIA in the states and ISO for Europe and most of the other countries

Why would the it guy say it doesn't work? He can say he doesn't like it...or whatever but if the cabling is A on both ends..workstation and patchpanel then it is no different transmission wise from B, just transposed pairs. Makes no sense. The guy wouldn't know the difference unless he looked at how it is terminated.

I think he had a bad patch cord or a bad switch because he declared "nothing works since you rewired it" Then proceeded to open up the jacks as well as check the patch panel.

Butch Cassidy - now you've seen a 568A patch cord. Not Chinese crap. From Belden, a reputable manufacturer.




Someone does or uses something different from what you're used to and its wrong? I think in my past 20+ years in doing this, I've replaced only a handful of patch cords, and most of those were ones under desks that people were rolling their chairs across,,, and those were not done on overtime or for free.

Thanks for the closeup of the cable printing. I can see that it is CMR 24 AWG stranded. I suspect this is category 5a because it is using 24 AWG wire not the thicker 23 AWG wire required for Cat 6x.
It says "Gigaflex" but I believe 5a is rated for gigabit ethernet. So far so good.

I can't see the colors in the plugs. Can you turn the plugs over and take a picture from the side without the tabs? From what I can see, it looks like white-orange orange white-blue blue white-green green white-brown brown. That would make it category "amateur".

By the way the wire is marked Belden, but that does not mean Belden made the whole cable including the terminations. This might be a homemade cable.

Wow, a homemade cable, really??? Part number is AX350002 (now updated to C501106004) - check it out on Anixter, Graybar, etc.

Cable is labeled: Belden Gigaflex PS5 Modular Cord --4PR/24 Stranded E108998-S C(UL)US CMR -- Verified (UL) Cat 5E -- ROHS 14002

Remember, from this side, for pins 1 to 8, you are looking at it right to left which is White/Green, Green/White, White/Orange, Blue/White, White/Blue, Orange/White, White/Brown, Brown/White - AKA 568A. In the picture you can see the orange wire crossing over to the 6th pin. You cannot see the colours from the other side due to the manufacturing.

Although the Cat 7 cable is an ISO/IEC 11801 wiring standard for 10 Gb/s over a maximum of 100 m, the IEEE, which develops ALL USA wiring standards has concluded a Cat 8 standards study within the P802.3bq Task Force. This work was concluded on June 30, 2016. The Cat 8 cable standard outlines the transmission of 25 Gb/s and 40 Gb/s data over ethernet using copper cable. Click Here

The IEEE sets the technical standards for the ANSI TIA/EIA to implement in structured wiring proforma, known as 5xx, 6xx and 7xx (such as TIA/EIA 568A or 568B wiring). At this time, I don't know the TIA group which will publish the TIA/EIA standards for Cat 8.

If you thought the specifications for ISO/IEC Cat 7 standards were tough, read the standards which have been adopted by IEEE SA for Cat 8.

Rcaman

Easy enough to fix. When they see my charges for installing CAT7 or 8 the cost of fiber even with the expensive electronics will look like a bargain.

-Hal

What is Cat 5a and Cat 6x?

x is for xylophone

Cat- X has to be the best thing for us since the bottom is dropping/has dropped out of the equipment market.

Every couple of years you've got to rip out and replace the wiring! Joy!

Why do corporations feel they need faster and faster networks?

Type out "The quick brown fox..." and save it in Notepad, Wordpad and MS Word. No embellishments, Now look at the difference in the size of the files.

Email used to be plain text. Now no one sends anything that's not in Word with enough fonts and pictures to look like a ransom note.

Celebrate this! It's keeping you in business.

Sam

After a little checking I found out that you can now run 2.5GBase-T (2.5 gigabits per second) on cat 5e copper cable. You can run up to 5GBase-T on category 6 cable and up to 10GBase-T on category 6a cable. All of these are rated for up to 100 meters of cable length.

Yo can also run 10GBase-T on Category 6 up to 50 meters.

All of this is from the encyclopedia that anyone can edit.

Of course you need to have the matching terminations and not untwist the cable ends too much etc.