Multiple T1 transmissions on Cat5E

My question is regarding the transmission of multiple T1 signals on Category-5E cables bundled together. The reason I have this question is one of my data center customers decided to extend (48) T1 lines from the Telco room to IVR equipment over (48) Cat5E cables. Then terminate on standard 48-port RJ-45 patch panel. The intent is to run each T1 on an individual Cat5E cable (ie. Tx & Rx within each cable). My cusomter claims that there would be no intereference between all these T1 lines running together in the cable tray. The distance is over 100 feet.

Normally, the way I design T1 cable runs is to either use 56-pair ABAM and terminate on a DSX panel; or substitute the ABAM with Category-3 and terminate each Cat-3 bundle one for Tx and one for Rx.

I was taught by an SBC engineer once that running more than 6-7 T1s in individual Category-5E/6 cables next to each other will cause interference or cross-talk. Is this true from your knowledge and experience??

Reply to
Tech Geek
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You've been doing it right, except even the ABAM should be separate bundles for TX and RX.

If the cable does not extend beyond a single point ground system you do not need to shield the cable.

I.e., if it is between racks in the same row and they all share one common ground wire going to the building ground (which would normally mean there is a copper strap across the tops of each rack, bonded together), then UTP cable between those racks is okay.

Which is to say that CAT5 cable would be usable, though technically even then it should be *only one* signal in the bundle! (Obviously CAT5 is the *wrong* cable, regardless.)

UTP should not be used between rows. Between separately grounded areas, ABAM is used and TX and RX are not placed in the same bundle.

The difference between doing it right and just doing something that will probably work may or may not affect them. But 48 T1's is not just a couple of them, and 100 feet is a lot farther than between a couple of racks. They are pushing it. If they also have a few hundreds of other digital cables running around (similar to the typical hostile environment in a telco office) they shouldn't even think about doing things the easy way!

Reply to
Floyd L. Davidson

This sounds like something one of our beloved DataBoyz would think up, doesn't it?

If I were planning this adventure I'd go find some appropriate ABAM cable or one of th eseveral 32 pair T-1 screened cables for this job. If they have the money, I'd include a DSX panel at each end and I'd cut down the output of those panels on a quality 110 block. At that 110 block I'd intermix the Tx and Rx leads so jumpers could be run with two pair cross-connect wire with the Tx and Rx adjacent to each other (that is, I'd terminate the transmit leads on pair 1, 3, 5, 7, etc. and the receives on 2, 4, 6, 8, etc.)


Reply to
Al Gillis

You *can* do a lot of things that are downright stupid, and that is one of them!

I might work, and it is definitely not "spec". Which means it might not work too. The problem is that it might work today, and everyone walks away thinking it is okay. Then next year something else is installed, and all of a sudden there are problems with this system... ooooppps.

That is the reason to follow specs the first time, so that you don't need to redo it to specs later.

Nobody does that with multi-bundle cables *inside*. And while it is DS-1 that is being discussed on this cable, the actual signal on outside plant cable is T1. Two different beasties.

Reply to
Floyd L. Davidson

That's overkill, Al. You absolutely -CAN- run multiple T1s in Cat5. The trick is to keep all your Transmits together in one bundle and keep all your receives in another. It *DOES* work. You can even use all 4 pairs and put 4 T1s in 2 cables. May not be "spec" but it works. I've run multiple 2.048 mbps E1s in 24-pr Cat5 almost 900 feet and never had a problem. Just keep your transmits and receives separated in different cables and there will not be a problem. If you can do it in separate binder groups in a 900-pr voice cable you sure as the dickens can do it in Cat5. Just follow the same rules.

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At the LEAST.... Put all the TX's in one bundle; all the RX's in the other. You likely can use 12 CAT5's in each direction...

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