Nortel Line Side T1 and Dialogic D/240 PCI T1

[CoderRob]

Nortel Meridian programmed with line side T1's going to 3 Dialogic D/240PCI T1 cards. They have set up a linear Hunt Group that spans extensions 3500 to 3571 (all 72 channels; if the dialed extension is busy it just rolls up to an available channel). Typically they all just dial the 3500 base number.

If the user dials 3500, they very often get static on the line or even more often they see situations where the audio fades out completely when playing (though it does not truncate or terminate early; the timing remains the same in terms of the Play() function call completion). But, if the user dials into an extension in the 3501-3571 range it works fine every time (not sure what happens if 3501 is in use and has to roll up to 3502, I am getting them to try that one, but 3500 almost always exhibits the problem). Also, sometimes one span of 24 channels will ring busy but unplugging and reconnecting the RJ45 from the switch solves it immediately (clock slip?).

The thing that I do not understand is this: the switch programmer tells me that the Line Side T1 is NOT providing a clocking signal. Don't the Dialogic telephony cards and the switch *ALWAYS* have to agree on a common clock source?

Thanks immensely for any insights, I am at the end of my rope!

Rob

 

[Gumpus]

LD 60 LCNT?

are the counters on the T-1's clear? I would suspect the Dialogic cards haveing a bad port. Is this for a VRU? Does the T-1 wind up with a analog channel bank?

I would try changing dialogic card #1 with card #3 and see if the problem follows the card.

gumpus

 

[NTOldTimer]

There is an interface (MMI) to the Line Side T1 card that is fairly easy to connect to. This could help with identifying T1 related troubles. Has the PBX guy showed you this? Sounds to me like you may have a bad dial logic board, speaking to the static/noise issues. We always like to think that the Nortel stuff is good and the "third party stuff" is causing the problem but sometimes it is us. Do you have more than one line side card that you can swap around to see if the problem moves?

 

[ChristyJ]

When did you buy the dialogic boards?

Intel have a bulletin available relating to SRAM issues on the board which may cause problems for cards manufactured in December 2002.

contact your reseller or Intel direct.

CJ

 

[CoderRob]

Thanks for the reply.

One can never be sure (particularly while troubleshooting a problem remotely on the phone), but I do not think that this is caused by a bad Dialogic card; the problem only happens when the Hunt Group has to roll to another number. I can dial into specific extensions all day long, but as soon as I dial into one that is busy (requiring it to roll up to another extension) the problems with static/pops/fading audio occur.

I am having the on-site guy rotate the T1 cables around by one to make sure that the problem does not follow the Dialogic card, but I do not expect it to move. I think that something about the hunt group forwarding (perhaps combined with the fact that the switch is not providing a clock signal to me) is causing this...

Thanks,

Rob

 

[CoderRob]

Just a small update after a little more troubleshooting... This audio noise/fading problem sticks with the particular 24 channels from the Nortel switch, swapping cables to Dialogic cards does not change a thing. While there are three spans of 24 channels each, this problem will only happen with the first span, and only when the linear hunt group had to "roll up". In other words, things work fine when I dial "3510" if 3510 is not already offhook. If 3510 was busy, however, and the hunt group has to "hunt" (probably up to 3511), the problem will manifest itself. But again, not to be too redundant but this only happens on the first span of 24 channels, the other two spans work fine whether they had to hunt or not.

Even though it would appear that I have an issue with a line side T1 card in the switch or maybe even the slot containing that card, I cannot completely reject the fact that the lack of a clocking signal from the Nortel switch could be a factor in this. Switch-guy tells me that he cannot provide a clock signal to these lines but I am not sure why.

Thanks in advance for insights,

Rob

 

[vztech]

I'm not to familiar with Line side but I would asume they are getting their clocking of the internal clock or what ever ssck 0 is set to.

 

[Avaya911PLM]

Actually, the M1 only sees the 500 port side of this card. The T1 side has no connectivity to the PBX, cannot be managed in LD 60, nor does it look at the clock. It is just a T1 MUX. As was stated earlier, the T1 side of the management is done via the MMI interface on the back.

--
Fletch

http://PBXTech.Net

 

[CoderRob]

>> "The T1 side has no connectivity to the PBX"

So what does this mean for me in terms of getting a clock signal? Are you saying that I simply *cannot* get a clock signal from the switch?

Thanks,

Rob

 

[Avaya911PLM]

Right. Think of it this way. The card is sitting in an IPE shelf, there is no Common Equipment Presence there, and it is not extended there via cabling. It is really just an 'in-skin' MUX. Therefore the T1 on the backside of this is all alone, the switch really doesnt even know it's there.

--
Fletch

http://PBXTech.Net

 

[CoderRob]

Very enlightening. So do you know if I can get the switch to look at a clock signal generated by the Dialogic cards? How can a T1 line stay out of alarm mode without a good common clocking signal for both sides? Am I missing something?

Thanks a lot in advance,

Rob

 

[Avaya911PLM]

It has an internal clock, and will either clock the far end (default) or have the far end clock it. Remember the T1 is isolated from the PBX therefore it's clocking does not have to sync with the PBX just to whatever it's talking to.

--
Fletch

http://PBXTech.Net