atcomsystems.ca/forum Forums Wiring - Telecom Carriers - Trunks & Services T1's, CSU's and DSU's How can telco see b8zs signal on ami/d4 ckt?

I have a T1 plugged directly into a dialogic card configured for ami/d4 and telco states their seeing b8zs signals. They've taken the ckt down and tested clean to csu. The telco indicates that the equipment is configured for b8zs/esf but it isn't. I've reconfigured the equipment again for ami/d4. What could be causing this? (the csu was disconnected from ckt to exclude this as a possibility)
Thanks in advance.

Was the T1 itself ordered as B8ZS/ESF? If it was order and built that way, they’re seeing B8ZS ‘cause that’s what it is…

You’ll have to check the way the T1 order was placed to make sure it’s AMI/D4. That’s pretty rare now days.

Also, fair warning… I moderator will be along shortly to ask you to update your profile. They always do.

Thank you for your response.
I can confirm that the circuit was ordered as AMI/D4. There are 8 other AMI/D4 ckts working properly, terminated to the same piece of equipment but using separate dialogic cards for each T1.
This specific dialogic card defaults to using AMI/D4 and I haven't configured it for anything else. Not sure why the telco is seeing b8zs framing errors.
Telco did an intrusive test to the csu last night and it came up clean. Any ideas?
Thanks.

You might want to put a hardwire loopback for them to test to. If they see b8zs, the local card is probably misconfigured.

What problem is it causing? b8zs will pass your ami signal, but it won't work the other way around. If they are seeing a flashing b8zs on a tberd or a similar test set, that is not a b8zs signal. On a b8zs signal the b8zs light will be lit all the time. But the bottom line is what's the problem? It won't be just the lec sees b8zs.

The CO circuit is config'd B8Zs up to the NIU. CSU probably doesn't care. I have had to upgrade many sites as AMI/D4 is not supported through many of the new Muxs at satellite COs. Don't know of any carriers in my area installing/supporting AMI/D4 format any longer on the span.

If you've had them terminate to a smart jack, then you can tell by the LED's what it's seeing coming from Dialogic.

What Dialogic card are you setting up and what version of the Dialogic driver? The new DMV cards don't handle AMI by default, it takes a bit of a hack.

I'm curious as to what the solution is to this problem once they get it fixed. (If they really tell you) This just gets more complicated all the time with new technologies. My guess would be that there are several hops between the point to point and a tributary on a DCS, GR303 or fiber mux is not provisioned correctly in the process of delivery. These problems can test good to a loop from the field and still not be correct in a colo somewhere. On the other hand Rob may also be correct since I do not know the Dialogic, I'm just offering another possibility.

As a C.O. technician I deal with mis-options on an almost daily basis.

Have the telco try to run an "All 0's" test pattern to a loopback plug inserted into the smartjack from all test points in the circuit's path.

All 0's will not pass through any device optioned as AMI.

If they get a good signal back, then the circuit is optioned as ESF/B8ZS. If they cannot see the pattern come back, then some part of the circuit is optioned D4/AMI.

As far as if B8ZS can pass through an AMI mis-option and vice versa, in my 16 years as a C.O. tech, I have never seen a signal pass cleanly through a piece of mis-optioned equipment.

A B8ZS mis-option on an AMI circuit will result in Bipolar Violations to the equipment on the side facing the mis-optioned equipment.

An AMI mis-option on a B8ZS circuit will result in CRC errors being registered by the equipment AND the equipment on the opposite end will be reporting "Far End CRC Errors".

Dexman, AMI will pass through B8ZS optioned equipment, B8ZS will not pass through an AMI optioned circuit. That doesn't mean you can put AMI into a switch optioned B8ZS. It will pass through the circuit fine until it reaches the equipment at each end. His question was the lec was seeing B8ZS from his AMI optioned equipment, which if his equipment were optioned AMI they would not. They may get an intermittent B8ZS light if the zero's density is exceeded, but that is not the same as receiving B8ZS. Running all zeros to a loop back wouldn't prove anything if the lec is saying they are seeing this from his equipment. In my experience the lec was always passive, they would just pass whatever was given, the problem came when they would test, as they would test the circuit as ordered. Once you got it through their heads that they didn't care what went through them as they had nothing on the circuit to do the AMI/B8ZS optioning then you could get down to what the real trouble was. That's why I asked, what is the trouble? Because I'm seeing B8ZS is not a trouble. Now this is all from my experience when this went from an AT&T piece of equipment through to an end user. I'm not talking a lec switch to an end user. Sorry this is so long. Bottom line is we still don't know what the trouble is he was/is having.