Static and fading audio when dial hunt group / pilot number

[CoderRob]

Nortel Meridian switch connected to three Dialogic D240 T1 telephony cards. The switch guy set up a hunt group (not sure on that terminology, but dialing the base extension of 3500 rolls into one of 72 T1 channels (3501-3571). If the users call into 3500 (even if it rolls to a higher extension) they almost always get static on the line and fading audio (the audio is still playing, but they cannot hear it). But if they dial directly into one of the other numbers associated with the hunt group (like, say, 3510) then the problem never happens.

I am a PC programmer so I am no expert on switch programming, but is there any chance that there is some sort of a tie line issue here? I am at a loss, and the Nortel site is slow and exceedingly unhelpful.

Thanks in advance,

Rob

 

[mattKnight]

My first check would be to check and alter the encoding system from A-law to mu-law or vice versa (I can never remember which one for which area, but...)

If I remember correctly, some releases of Dialogic system software reset the encoding every time any other parameter is altered. But I do have a poor memory !!!

Take Care

Matt
If at first you don't succeed, skydiving is not for you.

 

[CoderRob]

I have a little more information now...

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(...) API 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, but the Dialogic DCM resolves the "Derive Clock From" value to "FrontEnd_1" for the card that is set as the "Master" on the clocking (with the other two boards being Slaves)... does this look like I am getting a clock slip or something else entirely? Don't the Dialogic 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

 

[OldPhoneGuy]

I don't know much about Nortel and even less about Dialogic, (I'm an old ATT/Lucent guy) but I do know this: If the Nortel has T1's from the network (MCI, Sprint, AT&T, etc.) The Nortel needs to clock off the network and the Dialogic needs to clock off the Nortel. Even if the Nortel is clocking off of itself (no T1's to the network) I would have the Dialogic clock off the Nortel. Someone has to be master and someone has to be slave. Otherwise you will get static, disconnects and dropped data calls between the two.

 

[CoderRob]

I still think that I have some clock source issues, perhaps unrelated to this particular problem, but I have a little more data:

The problem (static, popping, fading audio) only occurs when the dialed extension is busy and the hunt group has to "hunt" for an available line. So if I call into 3510, leave it connected, then on another phone call into 3510 it will roll up to 3511 and the bad audio problems occur. It never happens if the dialed number is available.

Does this provide any clues?

Thanks,

Rob

 

[mattKnight]

Um....

My understanding would be that if you busy ex 3510 and then dial 3510 again, you should get busy tone back (or some other signal)

Why do you get extension 3511 answering?

The point of a hunt group is to cycle through a list of extensions (how it cycles depends on the type of group) and allocate a call to a free line.

As you are not using the hunt group by dialling 3510 (directly) and getting an answer from extension 3511, I would check that there is no other forwarding going on.

Let us know more...

Take Care

Matt
If at first you don't succeed, skydiving is not for you.

 

[CoderRob]

The way that the switch guy described it to me is that this is a linear hunt group that spans extensions 3500-3571, and dialing into one that is busy results in it rolling up to the next available line (and this is indeed the case as the phone displays the extension that you ended up with).

From previous experiences I am more accustomed to sort of a "pilot number" that is sort've a virtual/phantom extension but that is not the case in this scenario. I am speculating that this problem is caused by something that happens with the call being forwarded to the next line, and the fact that the line side T1 is NOT providing a clock signal to me may also be part of it.

Thanks again for the reply, this site is very helpful.

Rob

 

[jerryreeve]

If you are still having problems with this I would suggest that you check out forum798 they might be able to give you some suggestions.

JerryReeve
Communications Systems Int'l
com-sys.com