Question about Adtran ISU 512 Multiplexer

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I have a ADTRAN 512 modem in use with a Tandenberg VTC terminal. It has (3) single pair (U Interface) ISDN BRI lines feeding it. From the Nortel PBX switch, those lines are two 64K bearer channels each, totalling 128 x 3 = 384 Kbps. When dialing into any of the (6) SPID's, it will try to bond for the 384, but will not go above a single 64K. I have verified modem setup, Tandenberg setup, and PBX setup. All appear to be correct. I am even able to do video both ways, and stay connected, but only at 64K. My question may be more of a trouble isolation one, than the root of the problem, but ultimately need to arrive at both answers. I manage the telephone switch, normally verifying that part, and leave the other part to the outside folks. In this case, there is noone to leave it to, so I am trouble shooting the whole picture. I cannot find anything in the telephone switch that is responsible for bonding. I am pretty sure that bonding has to take place at the ADTRAN level, and not the phone switch, or Tandenburg equipment. Can you confirm, or deny that? It's, of course possible that we have a bad modem. We did try a second one, but I am not sure we ran the same tests. So far as I am aware, the PBX simply supplies the (3) DSL U Interface lines, at 128Kbps each line, and it is up to the ADTRAN to add up those channels during bonding. If you can think of any other things to check, I would apreciate your input. The ADTRAN is setup for 384K bonding, and 6 channels.

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SOURCE: front panel dialing

You need to check in the 'network options', 'dial line', #4 'dial options' to see if you have the front panel function enabled.

As for not being able to call ISDN in the US, that is a possible routing or long distance service issue you need to have looked at by your service provider.

Posted on Jan 06, 2009


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If this was working on the DSL let me know. I don't know the location but obviously a separate phone jack is the easiest. Let me know. If this helps you fix it you can rate this as fixed. If you are just going to rate this as helpful I'd rather you please not rate it and just add a comment and say thanks for the info.
If you need more help just add a comment and I'll be glad to assist you further. Thanks.


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Front panel dialing

You need to check in the 'network options', 'dial line', #4 'dial options' to see if you have the front panel function enabled.

As for not being able to call ISDN in the US, that is a possible routing or long distance service issue you need to have looked at by your service provider.

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