atcomsystems.ca/forum Forums Wiring - Telecom Carriers - Trunks & Services Cabling Telephones Systems Wiring T-1 crosstalk

I have about 25 DSX-1s moving from the MPOE to the CPE in the next room; the runs are about 25 to 30 feet... in cat 5.

I don't have any *apparent* crosstalk problems at the moment, but I'm sure eventually I will, and they'll say "you're running your DSX-1s *how*??"

Is it actually worth my rerunning this as 4 25-pairs, 2 TX and 2 RX between my patch panels?

AT&T used to (may still) make a 25 pr shielded cable. (Cat 3 probably. Cat 2 maybe.) We ran tens of thousands of T-1s with them. Maybe hundreds of thousands. No problems.

Run 2 of them. 1 for xmits, 1 for rcvs.

Done and clean. If you want to provide for the future, run 2 more.

Sam

To clarify, I thought you could run separate-jackets without needing the shielding...?

I've seen the shielded 2-pair stuff that's ridiculously expensive, but I thought that 25-pair all TX (or RX) didn't need to be shielded; that's not the case?

The specific thrust of my question was: assuming that having TX and RX in separate jackets is in fact good enough, do I really -- with current generation CPE -- need to worry about rewiring it at all, or will I actually get by ok with just having both sides of the DSX-1 in a Cat-5 cable, which is the current arrangement.

We always ran shielded for T-1s. Back with GTE we ran General Cable T-1 cable". It was an 8 pair cable about the size of 50 pair. Each pair was individually shielded and there was an overall braid. The cable supported 4 T-1s.

In my present incarnation we run 2 AT&T cables. Either 2 shielded 6prs or 2 shielded 25 pairs (all 22 AWG).

We've found that while you can sometimes get away with unshielded cable, it's not worth the hassle when something pops up later on and hoses traffic.

Do what you like. Your mileage may vary.

Sam

Interesting.

I may have misread my sources, but I thought the shielding was only required if you were going both ways in one cable. As it is right now, nothing is shielded, and I'm going both ways in one jacket, and I don't see any appreciable error counts.

I'll look into the 25-pr shielded.

Not that 25-pr Cat 5 unshielded isn't expensive enough.. :-) Thanks.

Why get waste the money on cat 5?

Well, as it happens, because the place I was buying it from a) didn't have any Cat-2 or -3, and b) does T-1 cabling themselves, and recommends/specs Cat-5.

Yeah, I know that's not a great answer, but when you only need 300ft, what do you do?

You should probably just stick with what appears to be the norm, especially for short runs like that. We see T1 (DS1) extensions done with a single CAT5 wired to 568B standards all the time. Does this meet technical specifications? Not really, but these circuits (well their designers) have learned to make them much more tolerant of today's assumed standards.

I don't like it, but what you need to do can be done using these people is probably your best bet. Technically, each pair should be shielded and you should be using jacks wired in the RJ48X configuration. Unless you hire someone who truly knows how to do it right, you should probably just stick with what you are doing now and assume the risk.

I had a customer who tried to jump 50 ft between a dialer and their PBX using a standard Cat5 and wondered why it sounded like crap. After trying another T1 board on both pieces of equipment, we tried another jumper. All he had that was long enough was longer - 100 ft. It sounded worse, when I realized what the problem was all along - the TX and RX in the cable weren't shielded. I had him rewire with two lengths of Cat5 kept apart from each other and all was solved.