Summary:ASTERISK-00357: Rhino Channel Bank Appears To Break DTMF
Reporter:jayson (jayson)Labels:
Date Opened:2003-10-06 11:31:39Date Closed:2011-06-07 14:05:25
Versions:Frequency of
Environment:Attachments:( 0) foo.raw
( 1) foo.wav
( 2) zapata.conf
( 3) zapata.dyn
( 4) zaptel.conf
Description:We recently acquired a Rhino-brand channel bank.  It is, really, about the simplest device I've ever seen (managed in the most minimal sense).  Upon connecting it to our CO T1, it worked flawlessly.  When we connected it to the PBX T1 (running out of a T400P), everything worked fine--EXCEPT that Asterisk completely failed to pick up any DTMF tones at all.


When extensions are picked up, I get the appropriate stuttered dialtone.  CID MWI appears to get set (haven't tested this extensively).  When I use the spool/outgoing/ interface to dial one line and have it dial another, it correctly rings, detects pickup, rings the other line, links them, and detects hangup.  It just fails to pick up DTMF.  When connected, other people can even hear the DTMF (and the tone sounds correct) when you press a button.
Comments:By: John Todd (jtodd) 2003-10-06 15:06:35

Can you include your zapata.conf and zaptel.conf files here?  Please remove comment lines that were not added by you for brevity.

By: Mark Spencer (markster) 2003-10-14 05:09:15

Is this still a problem?  Have you contacted Digium support?  I think that's the better place than here for such a request.

By: jayson (jayson) 2003-10-14 12:41:21

This is still a problem.  I've been working with Rhino on this one first.  I'm wondering if this isn't some sort of problem with the tone recognizer (or maybe the Rhino does something odd to the waveform).

I had not gone to Digium support yet, as we didn't have one deployed (i.e. no customer to pay for it).

By: Mark Spencer (markster) 2003-10-16 07:10:41

Out of curiosity, have you tried different phones?

By: jayson (jayson) 2003-10-21 08:36:22

Good call Mark.  I pulled out the lineman's phone and hooked it directly to the termination block.  Sure enough, it worked fine (and for the record, the remote phone rang, picked up, talked, and hung up fine).

I'm bringing in another phone to see if it is just the Aastra PT390s that have this problem.

I can hear people reasonably well, but DTMF just fails.  Does this mean I need to turn up the gain slightly?  Or is it too hot (clipping the tones)?  Or do you think it has something to do with the phones?

By: jayson (jayson) 2003-10-21 14:36:09

I've run ztmonitor on a channel to snagged one of the times that it failed to recognize the tones.  I'm attaching the raw and WAV versions of the file to this ticket.  At first glance, it didn't appear to be clipping to me.

By: jayson (jayson) 2003-10-29 09:01:37.000-0600

This is fixed.  Apparently the signal was coming in too hot.  Not sure why, but when I added txgain=-6.0, the problem appears to have gone away.

After examining the sampled wave file, it is unclear to me why it didn't work (the sound appears okay to me), but this definitely fixed the problem.  Although, can anyone tell me why this worked?  It is unclear to me why dropping the txgain so much would do this.  Do I have the rx and tx sides confused?  It seems to me this should lower the gain on signal coming out of Asterisk, not coming into it.

As such, you can close this ticket if you consider it resolved.  If you don't, I'm willing to help track this down if you think this is a sign of some weirdness in our DTMF detection.

By: John Todd (jtodd) 2003-10-29 11:20:41.000-0600

I'll leave this open for a few days or until Mark takes a look and gives you any answers.

By: x martinp (martinp) 2003-11-03 16:35:12.000-0600

Do you have the gains on the channel bank set up high ?

By: jayson (jayson) 2003-11-04 16:15:04.000-0600

No.  That's the thing.  Some of the runs are very short and very low resistance.  The thing is, the signal didn't APPEAR to be clipped in the captures I did.  I'm not sure if it is something in the echo cancelling, something in the phone itself, or the goetzel filters--but something is preventing the DTMF from being processed.

On a side note, I've noted that there is negligible difference in volume on the phone.  I'm not sure what, but I'm wondering if the phone has an amp in it (possibly an amp that causes echos that trigger talkoff supression).