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Extending T1 from a DeMarc 2
- Thread starter cmapp
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1
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daronwilson
Vendor
I just put in such a link, and checked before hand. In the past we have just extended the dmarc with Cat5, I've not had any problem. However on this install the customers computer equipment vendor specified actual DSX-1 cable. The cable is two pair, individually shielded.
Now..termination. On this job I had several different vendors on site as we were connecting some wireless T1 equipment to a PBX t1 card. There were many opinions on how to terminate. What the two vendors agreed on finally was to not used the ground at all. So we ended up terminating the shielded cable on modular RJ-48 jacks, and letting them connect their equipment to them.
Personally I don't believe that to be very effective, the shield should be terminated and grounded on one end at least.
You might very well get the T1 to carry just fine on Cat5 at that distance. The T1 (depending on configuration) will use pins 1,2 for one direction, and 4,5 for the other direction (or maybe 7,8). So you can see by those pin numbers that a standard Cat5 cable keeps tx on one pair, and rx on another pair. However, DSX-1 signals are very picky about balance. Newer Cat5e has different twist rates for different pairs. In short there could be a balance problem, though I have not experienced it.
Also on some installations, I find it just easier to relocate the telco's equipment on regular telephone wire and have the actual demarc where I want it.
There must be more than one opinion or method
Daron J. Wilson
Telecom Manager
LH Morris Electric, Inc.
daron.wilson@lhmorris.com
Now..termination. On this job I had several different vendors on site as we were connecting some wireless T1 equipment to a PBX t1 card. There were many opinions on how to terminate. What the two vendors agreed on finally was to not used the ground at all. So we ended up terminating the shielded cable on modular RJ-48 jacks, and letting them connect their equipment to them.
Personally I don't believe that to be very effective, the shield should be terminated and grounded on one end at least.
You might very well get the T1 to carry just fine on Cat5 at that distance. The T1 (depending on configuration) will use pins 1,2 for one direction, and 4,5 for the other direction (or maybe 7,8). So you can see by those pin numbers that a standard Cat5 cable keeps tx on one pair, and rx on another pair. However, DSX-1 signals are very picky about balance. Newer Cat5e has different twist rates for different pairs. In short there could be a balance problem, though I have not experienced it.
Also on some installations, I find it just easier to relocate the telco's equipment on regular telephone wire and have the actual demarc where I want it.
There must be more than one opinion or method
Daron J. Wilson
Telecom Manager
LH Morris Electric, Inc.
daron.wilson@lhmorris.com
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TX and RX will interfere with each other if they run together over long distances. It's best to either sheild them from each other using the DSX cable or a cheaper easier method would be to use 2 CAT-5's. Terminate the 4 pairs in the 1st cable to 4 RJ-45's TX. Terminate the 4 pairs in the 2nd cable to the 4 RJ-45's RX. This seperation of TX and RX into 2 cables is more than adequate to keep you from ahving issues. -CL
Guest_imported
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- Jan 1, 1970
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Here's a story for you all....
I had to install a router in a warehouse, and the telco put the dmarc on the wrong end of it. Being friday, there was no way I was getting the dmarc moved before the required monday turnup date. I would have to extend the dmarc myself.
With speed, I figured out the T1 pinout. Then I put ends on a 1000' box of cat5 to see if it would even begin to work. Plugged the box of cable into the demarc and Cisco 1750 and it pinged the home office. No line errors. Whee.
Some awesome rigging, riding 30' in the air on a forklift, and a load of swears later I had the wire across the warehouse. I'd used over 3/4 of the 1000' box. And it worked.
This was all a long time ago, and it wasn't a pretty fix. I was just getting the job done, and I wouldn't do it again. But ever since then I hear all these factoids about cable length line noise wire pairing etc. But I got it to work knowing nothing, and sometimes I think the only reason it did was because noone had yet told me it wouldn't.
Name withheld to protect the baffled!
I had to install a router in a warehouse, and the telco put the dmarc on the wrong end of it. Being friday, there was no way I was getting the dmarc moved before the required monday turnup date. I would have to extend the dmarc myself.
With speed, I figured out the T1 pinout. Then I put ends on a 1000' box of cat5 to see if it would even begin to work. Plugged the box of cable into the demarc and Cisco 1750 and it pinged the home office. No line errors. Whee.
Some awesome rigging, riding 30' in the air on a forklift, and a load of swears later I had the wire across the warehouse. I'd used over 3/4 of the 1000' box. And it worked.
This was all a long time ago, and it wasn't a pretty fix. I was just getting the job done, and I wouldn't do it again. But ever since then I hear all these factoids about cable length line noise wire pairing etc. But I got it to work knowing nothing, and sometimes I think the only reason it did was because noone had yet told me it wouldn't.
Name withheld to protect the baffled!
Adtran makes a piece of equipment called a T1 CSU-ACE for about $400 that will push a T1 around 600 feet on 2 pair of CAT 3 copper. Or 2 units can be linked together to go up to 5000 feet on CAT3. I have a campus install using the second method to push 4000 feet to the first MDF and I installed a second pair to extend the circuit 3000 feet for the 7000 feet total.
Have done similar things with cabling that wasn't 'supposed' to run as far as we run it. The trick we found was not to go near (6') to power conduits or florescent lighting. If we had to cross the path do so at a 90 degree angle. These simple principles don't eliminate the interference problem, they do help minimize it.
When the florescent lamps or ballast go bad look out.... Don't spend hours looking for a problem all the while complaining about the lights flickering. Fix the lamps first not a week later (did that...don't want to do it again).
When the florescent lamps or ballast go bad look out.... Don't spend hours looking for a problem all the while complaining about the lights flickering. Fix the lamps first not a week later (did that...don't want to do it again).
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