Pinouts for T1/E1 crossover cable WAS "RE: [Asterisk-Users] what cable to connect a legacy PBX to a TE410P ?"

[Rich Adamson]

> Can't anyone stop self-promotion and tell the poor guy what he needs.
> 
> A T1/E1 X-over cable using an RJ-45 (8-cond.) is pinned out as follows:
> 
> 1 - 4
> 2 - 5
> 3 - NU
> 4 - 1
> 5 - 2
> 6 - NU
> 7 - NU
> 8 - NU
> 
> NU = Not Used
> 
> I have not in my experience seen any problems with using a Good Quality
> Cat5 vs. Cat 3 (telco standard) cable for X-connects.  YMMV, but you
> should be fine. As far as the shielding goes, I use UTP cables and
> Connectors all the time and some of my X-connects run over 100 feet.

It would probably be helpful for everyone reading this thread to 
understand what the differences are in the two types of cables. 
Primarily impedance matching, twists per foot, shielding, etc.

For short runs, the use of cat5 vs proper T1 cables isn't likely to have 
any impact unless there is a fair amount of induction from electrical 
noise, etc. That can take the form of florescent fixtures, transformers, 
older CRT monitors, etc, etc.

On longer runs, the shielded T1 cables are likely to provide better 
results particularly if there happens to be any electrical noise.

Oh, and if shielded T1 cable is used, the shield at each end of the 
cable must be grounded. (Let's see how many can figure out how to do 
that via an rj45 plug. ;)