[Asterisk-Users] Re: Shielding of T1/E1 cables WAS RE: Pinoutsfor T1/E1 crossover

[Michael Collins]

> 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 cat5
vs
> T1 cables, I'd have to guess a single strand is used from two
different
> 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