atcomsystems.ca/forum Forums Wiring - Telecom Carriers - Trunks & Services T1's, CSU's and DSU's T1 Slipping

Hey guys hope you can help. I have a customer with a T1 (AT&T) is the provider and then local co provides the smart jack to site. It has worked with the old switch csu(adtran csu ace ) for 10 years with no problem. The reason for the ace was to convert esf to D4 (SF) for old switch .Then we replaced the switch in Feb. with new Samsung officeserv 500 and worked flawless till the end of september, when customer started complaining of faxes with more than 1 page dropping over the T1. I went to site called into At & t after a visual inspection and testing to confirm faxes didnt go through correctly. They told me they could see something on the circuit wrong on their end, they would contact me back. The customer had me leave site and wait too hear back. They reported the next day that they worked correctly and worked flawless for exactly 14 days. Problem re-occured and customer had me come to site, so I diagnosed and called At&t and they said they would "adjust" it , which I never got an explaination and it worked again for exactly 14 days,re-occured. they 3rd time At&t told the customer it is my problem. They actually set a vendor meet and brought a Tberd. We tested & their test showed them sending out a freq. of 1594001-2 would alternate, and showed our equipment returning freq. at 1594376 , off by about 25 hzt, with a slip about every 7-8 seconds. I replaced Processor card & T1 card with no change on readings.What can it be? Any ideas would be greatly appreciated...

A true slip can only be caused by CPE. Frequency shift or wander is a carrier problem. From your discription I'd say you have slips. They break the circuit for testing, and when they put it back together it works for awhile, because it re-syncs, typical slip problem. Check your timing and make sure you are slaved off the network.

Thanks for providing those symptoms in such detail. The impacts of timing slips are usually much more dramatic on fax calls, than on voice calls. Like Bill said, the circuit is only holding correct sync for a couple weeks, then then the fax calls are typically the first to go downhill, due to their superior dependency on precise synchronization. It's definately timing.

Have you verified you are clocking off the network? Not internally.

Just relized Bill beat me to it.

:thumb:

Did anyone read what the poster wrote?

They stated that they put a TBERD on the circuit and the carrier was generating clock at 1.59MHz. That is out of spec.

Period. Carrier has a clock-card failing. No other explanation.

CPE is getting timing from the network because it is responding and trying to keep up at 1.59MHz but can't keep it up indefinitely because that is so far out of spec.

Carrier has a problem, TBERD confirmed it.

That's why I said freq shift was a carrier problem. But what is discribed is a typical slip problem. Frequency shift is not going to cause a slip. I would hope the Frequency posted is incorrect, as you stated it is out of spec. I would say his 9 and 4 are transposed.

yeah guys sorry i wrote 159 , but u are correct it is 15443996 ? & ours is 1543976, I have the switch flipped to network, and even tried user while he was there with the tberd.I dont understand what else to do on this one I replaced the Processor card which does clocking & the T1 card ?

Are slips the only thing you are seeing? With a Tberd or anyother test set you won't see slips unless you time the test set off the network, just as if it were timing for a pbx. Network timing should be correct.

After re-reading your original post I've a few questions. Does this terminate into an AT&T switch? I'm assuming it does. Does the circuit run over the AT&T (old AT&T) network? If it does there is monitoring equipment on it 24/7 and they can get in at any time without breaking the circuit and see what's going on. Is there still an external CSU on this? And is it optioned correctly? I'm a little bit leery about the slip thing for the reason mentioned above. If it truly is slipping then it can only be your equipment causing it. I doubt it would work flawlessly for 7 months if there were originally an option problem. Next time this starts acting up, unplug from the demarc for a few seconds and plug it back in. If that cures the problem you definitely have a timing issue.