[CIA]

So I posted a few days back about some odd network issues a girl here was having, the end result being we are replacing a large amount of patch cables here at work.

So we bought 1000' of Cat 6 cable from Mohawk And I noticed that it's labeled 568b on the jacket. I didn't think that much about it. For no other reason then consistency we were wiring 568a for everything. After cutting about a hundred 18" cables and prepping them to have the heads crimped on, I started to notice that the 4 sets of twisted pairs were twisted differently. The brown set (the last set for both 568a & b) have very few twists, the green and blue pairs have a ton of twists, and the orange is somewhere in between the 2. I remember reading back in the day that part of what makes cat6 cable better is that it has more twists per inch to minimize interference.
So I started looking up more about t568a and t568b connections. While the info for what the connections should be is standard across the web, which way that is should be inserted into the rj45 head isn't. Some sites show the wiring with the click tap at the top, others with it at the bottom. If the cable and twists were all the same then it's no big deal, but since my accidental discovery of the different amounts of twists in my cable now I'm wondering... I'm not super worried about it for these small 18" runs, but for longer distances. I guess more twists means more cable so it's cheaper to make less twists on the little inner cables that aren't actually used for data.

So what is the correct way to wire a 568b connection? Since the brown is the least twisted does that place it in pins 1 & 2 or 7 & 8, and what side is actually up so I know what is actually pins 1&2 or 7&8?
Thanks.

[ghporter]

The difference between 568A and 568B is PURELY which colored pair of wires goes to which pair of contacts in the RJ45 plug. "Pair 2" and "Pair 3," the orange and green pairs are on pins 3&6 and 1&2 respectively in 568A while they're reversed in 568B.

Which means ABSOLUTELY NOTHING if you are consistent in constructing your RJ45s. The cable will work just fine as long as the same pair shows up on the same pins, whichever designated "pair" each is.

Here's a good Ethernet cable construction reference.

[CIA]

All this is true from a connection standpoint, where the head is actually crimped onto the cable. Over the weekend I checked out a lot of the cables here that are cat5e or cat6, and all but one manufacturer had 568a or 568b stamped onto the bulk cables. Further inspection did show that each cable had a different number twists per inch depending on the colors of the twisted pairs inside. The only consistent thing was across all but one brand (5 different kinds) the brown pair was the least twisted. So it seems that you should look on the cable to check which style connector you should crimp to get optimal performance out of the cable. Only one unmarked brand cable was labeled 5e and didn't have a 568a or b designation on the actual cable, and it's twisted pairs were all consistent, even the brown.

Just something I noticed. I don't think short runs are an issue regardless of what type of connection standard you use, but it does seem that to save money most cable companies specify what the "Preferred" connection is is based on the number of twists per inch. It saves them cash to use less wire inside. If anyone is using long runs, it's best to use the connection standard the cable lists on it's jacket. I don't have any high tech testing equipment to prove if it makes any difference or not, but it's one less thing to wonder about if you just do it right from the start.

Also thanks for the link to the head crimp standard.