(I hope this is an acceptable topic to post...I feel like I've done nothing but make waves -- unintentionally, I assure you -- since I got here. It seems to make sense to me that this particular topic is not a sensitive one that can't be discussed publicly and that should be in the Nortel forum, but if I'm wrong, feel free to move it to Installers.)

I've got my Asterisk-based SIP-to-MICS bridge up and running using the VMI, and besides the lack of caller ID, it's working brilliantly. I can even initiate call transfers and 3-way calling/conference calling on the Nortel KSU from the VoIP line.

However, I'm having a strange problem with it both recognizing and passing DTMF tones. It appears that if I don't enter in a DTMF sequence within the first few seconds of going off-hook (say, within 10 seconds or so), it stops listening for them or recognizing them. So if, for example, I pick up a phone connected to the VMI, go off-hook, listen to the dial-tone for 10 seconds, and then try to dial something, it continues to give me dial-tone and won't actually patch the call through.

This wouldn't be a big deal except for the fact that it also seems to have an impact somehow on DTMF passthrough for calls placed within the KSU that don't hit the trunk lines. This is especially having an impact with the phone or device hanging off of the VMI being able to navigate Nortel Voice Mail. If I dial voicemail from the VMI, and then wait to enter in my password/PIN until after the voicemail system has stopped talking at me, it can't hear the password I entered into the keypad and prompts me again before it eventually hangs up the call. If I begin dialing the password IMMEDIATELY after placing the call to NVM (without waiting to be told to enter my password), NVM accepts it and gives me the main menu! But if I don't immediately then navigate the menu to get to wherever I'm trying to go (new messages, etc.), it doesn't recognize the menu options I've selected!

One thing that I've discovered that I can do to "wake up" the DTMF detection in the VMI after it has fallen asleep is to flash-hook the line to get to the enter-feature-code mode, and then flash-hook it again without entering a feature-code to return to my current call-in-progress. The DTMF passthrough then works again for a few more seconds before it "falls asleep" again. This is, of course, extremely inconvenient.

The problem with the DTMF detection "falling asleep" at the dialtone largely isn't a problem practically-speaking because I have Asterisk configured to dial immediately after it takes the FXO port off-hook. But the DTMF detection/passthrough issue is still extremely problematic for IP/Asterisk extensions who want to be able to check their voicemail on NVM.

Two other things to note: First, if I call, say, an M7310 handset from the VMI, and enter in DTMF tones on the handset connected to the VMI (even after waiting for a while before entering them), they come through to the M7310 handset just fine. No problems there. So I'm at a loss to explain why it seems to behave differently when it is talking to the NVM than if it is talking to a regular Nortel handset. Second, if the VMI is placing a call out through an analog trunk line, DTMF works perfectly during the entire call. So I can, for example, call myself through the ILEC (going out through one trunk line and looping back in through a second), access NVM, and check my voicemail without any problems.

Anybody have any insight into this problem and what I might be able to do to overcome it?

-- Nathan