atcomsystems.ca/forum Forums Wiring - Telecom Carriers - Trunks & Services T1's, CSU's and DSU's T1 extend IW - how to test

Yes, the twin cable that you reference is quite common for circuit extensions. In order to work properly, the transmit pair for the circuit should reside in one shielded jacket and the receive pair should be in the other. These are usually four pair cables, meaning that four circuits can be extended in the single cable run.

In a perfect world, four transmit pairs reside in one cable and four receives are in the other one.

The cable shields should be bonded together and tied to the building's grounding electrode conductor, although any local ground connection at the service entrance will usually suffice. These cables should NEVER be bonded at both ends.

As for the jack pins with regard to grounding: Don't even think about that part. As long as the cable shielding is properly bonded to the building's electrical ground, this additional bonding isn't really necessary.

T1 circuits often arrive to the premises via thousands of feet of "CAT 0" copper cable, but once they hit the smart card, NIC, NTU, NTC or whatever they call them these days, the circuit must be treated a bit more gingerly.

You are correct in your assumption that a traditional CAT (anything) cable tester won't confirm proper operation of a T1 circuit extension. This is due to the fact that a T1 circuit isn't a LAN circuit; it is a network connection. These are completely separate aspects of the telecom industry.

I must commend you for even asking these questions. Circuit extensions are quite often misunderstood since they take on a whole new life once they hit that network termination card.

Okay the shields for each pair and for each cable sheath should all be grounded at the service entrance. I can probably get away with putting a screw into the shelf or cabinet right next to where I put my plug into the smart jack. I have seen that these cabinets are usually bonded to a good ground.

What is the best way to connect these foil or braided sheilds together so I can screw them down to the metal cabinet? What part would I actually use to make this connection? In other words, in actual physical terms, how do I bond these delicate aluminum or braided shields to the ground?

Bump -- Any ideas here?

The other day I saw an install where they used 2 pair shielded wire. The drain wires were all under a lug on the smartjack, and then just punched down on the block. I guess that defeats the purpose of a shield!

Ed said to ground the shields at the service entrance only, not at the extended demark. So what you just describes sounds like it should work. I guess you can just gather up all the drain wires (shielding) and twist them together and screw them down to the smart jack cabinet.

I think maybe if you have a small grounding clamp or small metal hose clamp, you can bend all the shield wires and foil back over the outside of the cable sheath and then clamp a grounding/bonding wire down to them.

I would sure like to know the official/profesional-looking/NEC way of doing this. Maybe that is it?

If any of you were around in the old days when network cabling was all done with shielded twisted pairs, you can enlighten us on how the shield bonding is done.

I have another idea. Instead of buying special twinned double-shielded T1 cable, can we use a couple of old shielded twisted pair cables? There is tons of this stuff laying around in phone rooms.

"and twist them together and screw them down to the smart jack cabinet".

"and screw them down under the ground lug on the smart jack cabinet IF the installer grounded the smart jack cabinet properly".

There is no NEC on T1 demarc extensions. What is regulated is what test parameters must be passed before telco can turn the T1 over to the customer. QRSS, 3/24, 1/8, ALL ONES, ZEROES, and POWER LOSS. Besides passing a combination of the 5 performance tests (determined by the type of T1 purchased) amd LOSS at the basic demarc (the Smart Jack) the same performance tests and loss must be passed at the Extended Demarc.

So you are sheilding, bonding, one side grounding as insurance. How you do it is your choice.

Use what ever wire you want sheilded, non sheilded, farm wire, open wire, barbed wire (in Wyoming barbed wire is called "twisted pair" as long as the tests parameters are met and maintained.

Okay, starting with nothing, what is the easiest and cheapest way to run these T1 tests at the extended demark?