atcomsystems.ca/forum Forums Wiring - Telecom Carriers - Trunks & Services Cabling Telephones Systems Wiring Reasons for 568B

I'm guilty of being an IT guy, Ed can ghostwrite under my name, haha

For what its worth I use 568A.

And, for those who don't know.

"A is a crossover and B is a straight-through"

But all my switches are Auto-MDIX so its better to have crossovers for when I need them and let the switches make them work as a straight-though.

Crossover? Straight-through? Those terms only come when you wire one end "A" and the other "B" last time I checked. Electrons don't care what color wire they travel on, as long as they are in pairs. The only difference to the guys with sight is when you cut the cable and try to terminate it on a block.

I happen to use "B" because the patch panels I buy are natively "B". That's where you terninate blue, orange, green and brown. You want "A"? Just terminate blue, green, orange and brown. Yeah, I'll get right on that. Since I'm a Leviton house, I've terminated for years as Blue, Green, orange to the right and brown to the left, keeping the white-color to the right for the first 3 and color-white on the left for the first 3. I can do that in my sleep (or is that hung over?)

The only problem is when you terminate voice jacks in 8-pin "B" and cut the cable down on 66 or 110 (or bix, eh?). Now the 2-pair voice line is blue-green instead of blue-orange. That usually only happens when someone else does the infrastructure, or the architect specifies 8-pin jacks in the scope, since if I'm doing the terminating, I'll use 6-pin voice grade jacks and terminate only the first two pairs, or two pairs per jack.

Carl

The only problem is when you terminate voice jacks in 8-pin "B" and cut the cable down on 66 or 110 (or bix, eh?). Now the 2-pair voice line is blue-green instead of blue-orange.

For those of us who are old AT&T guys we're used to that, especially when installing a Partner that uses two pair. You'll frequenty see it in old business that started out with a Merlin or Definity. Like Ed said, that's where 568B was born. You'll save yourself a lot of trouble by pulling a jack off the wall and looking at it before jumpering all other ends. Better yet, replace the jacks.

-Hal

"A is a crossover and B is a straight-through"

Is a quote from the post.

Thanks Ed. You never cease to amaze!

Around my house the saying (especially from my kids who have pulled a lot of wire and terminated it) is: "A is AWFUL and B is OKAY"

Canada uses the b standard. Not sure why but that was in all cases, 99 percent of the buildings. I remember once walking into a store, and doing a troubehoot call. One bad jack at terminal end. Repaired. Tested, no go mm looked at other end, it was wired 568a standard.

Make a correction, Canada uses 568A standard.

An ethernet "cross-over" cable has no designation, it is what it is. The w/o & w/g prs are swapped on one end. An A cable or a B cable can both be "straight thru" if they are the same on both ends.