Dry Pairs and 2601 Router

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Apr 29th, 2007
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We recently purchased 2 dry pairs from our telco to get 2 buildings hooked together that are 100 feet apart. We expected them to do the interconnect in the street cabinet but found they are running through the CO and using what looks like smart jacks in the phone room. I was told they have no signal on them and they are on pairs 1/2 & 7/8 with 0 & 22db (whatever that means). I tested the routers with a crossover ok and created cables to put the 7/8 pair to 4/5 (1/2 on the crossover). We get nothing but an alarm light when the remote router is put in place.

Is this even going to be possible using a CSU/DSU WIC? If so, what limitations are there as far as the telco is concerened? Distance and such...

Would something like an ADSL modem on both sides be better?

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scottmac Sun, 04/29/2007 - 11:22
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You are probably well beyond the distance a CSU/DSU can drive the line.

Do you have any idea as to the distance through the CO to your other building?

Black Box - www.blackbox.com (and some others, I'm sure) used to sell T1 line drivers that were good for ~ one mile or so ... maybe longer.

If you have a TDR, you can probably ping out the distance to within a meter or so. Once you have a fairly accurate distance, then you can start looking for devices that can drive the line that far.

Good Luck


robert.parsons Sun, 04/29/2007 - 17:06
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I have a telco person coming out tomorrow so will get the distance and take it from there. What is the max distance our configuration could go? I've read anywhere from 600 feet to 6000 feet. Big difference there....

I did try a TDR but couldn't get past their smartjack. It showed up open right there. I didn't try it at the smart jack though.

scottmac Sun, 04/29/2007 - 19:25
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A straight-up T1 signal is good for 655 feet over the proper media.

If you bought "dry copper," there shuldn't be a smartjack (and one shouldn't be needed).

A T1, as delivered by many/most/all telcos, actually comes from the CO as HDSL ... the SmartJack converts it to a T1/DS1 signal (and has other functions, like looping and protection from "environmental events").

That's why the telco can deliver T1/DS1 across many miles.

If you have dry copper, you should be / may be able to drive the copper feeding the SJ directly ... it's going to depend on what you've actually been delivered.

Have you tried turning on the clock ("Internal") on one of the CSU/DSUs ? There only has to be one master clock ... on dry pair, you will need to provide clock from one end or the other.

Good Luck



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