Michael Collins
2006-Apr-24 10:30 UTC
[Asterisk-Users] Re: Shielding of T1/E1 cables WAS RE: Pinoutsfor T1/E1 crossover
> I've never bothered to check to see if cat5 cables use the appropriate > mating twisted pairs or not. Since the pinouts are different for cat5vs> T1 cables, I'd have to guess a single strand is used from twodifferent> twisted pair groups. That wouldn't be cool, but in short runs it > probably doesn't have much of an impact. >IIRC, standard Ethernet uses pairs 1&2 and 3&6. The color scheme on "568B" is 1&2 = white/orange pair, 3&6 = white/green pair Most Ethernet cables then have the white/blue pair on 4&5, and white/brown on 7&8. An RJ45 carrying a T1 is: 1 - RxA 2 - RxB 4 - TxA 5 - TxB Assuming that you'd want RxA and TxA in the same twisted pair (ditto for RxB and TxB) then a cable would look something like this at each end: 1&4 = white/orange pair 2&5 = white/blue pair I don't know if there's an industry standard for T1 cabling to have a certain color pair for A and another for the B pairs. Electrically, though, the color is insignificant - as long as the correct pairs are twisted together then all is well. Does anyone have a "real" T1 cable that they can share with us the pin configuration? I am curious to know what color pairs are used. -MC
Andrew Kohlsmith
2006-Apr-24 12:01 UTC
[Asterisk-Users] Re: Shielding of T1/E1 cables WAS RE: Pinoutsfor T1/E1 crossover
On Monday 24 April 2006 13:30, Michael Collins wrote:> IIRC, standard Ethernet uses pairs 1&2 and 3&6. The color scheme on > "568B" is 1&2 = white/orange pair, 3&6 = white/green pair > Most Ethernet cables then have the white/blue pair on 4&5, and > white/brown on 7&8.Close. 10/100mbps Ethernet uses wires 1,2,3,6 but that is pair 2 & 3. Pair one is the pair up the dead center (pins 4&5), pair 2 is pins 1&2, pair 3 is 3&6 and pair 4 is 7&8. A T1 uses pairs 1&2, which is why you can't use a regular crossover cable for a T1 crossover, but you can use a regular ethernet patch cable as a T1 patch cable. As far as T568A and T568B... I always went by the Canadians using T568A ("Tee five six eight, eh?) and the rest of the world using T568B, which seems to be pretty damn close to reality. Honestly I think 568A is for patch panels terminating to one type of equipment (CPE) and 568B for inter-panel, but I'm not sure. Essentially they're different in such a way as they'll act as an ethernet crossover.> An RJ45 carrying a T1 is: > 1 - RxA > 2 - RxB > 4 - TxA > 5 - TxB> Assuming that you'd want RxA and TxA in the same twisted pair (ditto for > RxB and TxB) then a cable would look something like this at each end: > 1&4 = white/orange pair > 2&5 = white/blue pairCareful. You're mixing up nomenclature. If you are referring to A and B as "side A" and "side B" then you have the wiring mixed up. If you are referring to A and B as the differential signal components then you're right about the wiring. In either case you're wrong with respect to the pairing. :-) Pair 1 is the blue/bluewhite pair. Pair 2 is the orange/orangewhite pair. For a T1 crossover, the blue/bluewhite must go up the middle of one end and on the lefthand side of the other, and the orange/orangewhite pair must be on the lefthand side of one and up the middle of the other.> I don't know if there's an industry standard for T1 cabling to have a > certain color pair for A and another for the B pairs. Electrically, > though, the color is insignificant - as long as the correct pairs are > twisted together then all is well.Very true, you don't want to split pairs. Causes all kinds of nasties. As far as standards go: Yep; there are standards. And there are many to choose from. :-) The telco standard is as follows: Pair 1: Blue Pair 2: Orange Pair 3: Green Pair 4: Brown Pair 5: Slate Then you have the "group" colours: Group 1: White Group 2: Red Group 3: Black Group 4: Yellow Group 5: Violet 5 pairs with 5 groups gets you 25 pairs of wire. Hey, that sounds like a standard trunk! :-) Then you can get into bundle groups (which follow the pair wiring), and a grouping larger than that whose name escapes me that follows the group colouring... All in all you can get 625 pairs in a single trunk with only these ten colours. Google's got plenty of resources on this. "Telephone wiring color code" or somesuch. -A.
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