Random DTMF tones on PBX Side During Phone Call


We are experiencing issues with DTMF tones being generated during a call. The remote party does not hear them only the local party. We are using Yealink T28P phones with FreePBX distro. We have two client locations experiencing the same problem, one is on a PRI through the local telco company with a Digium PRI card and the second is on Vitelity SIP trunking. I’ve read about voices triggering the tones but I’m not exactly sure on how we should proceed. Any suggestions would be appreciated. Thanks so much.

What you are experiencing is called “Talk-off”, for the PRI connection make sure that relaxdtmf=no in the dahdi configuration and perhaps experiment with toneduration=(milliseconds) maybe 120 or more.

For Vitelity try using dtmfmode=rfc2833 and not auto on that trunk (but some other calls to bank’s IVR’s might start to fail, long story there, possible remediatiation make two outbound trunks to Vitelity and route only the recalcitrant numbers to the trunk with dtmfmode=auto)

You could also for debugging purposes add a logfile just for dtmf

dtmf => dtmf

and from your shell:-

tailf /var/log/asterisk/dtmf


You will find your issue is probably more common with female callers. @dicko’s recommendations should do the trick.

Off topic of the solution, this sort of thing was big back in the day if you like telephony history (who doesn’t):

Thanks dicko, not to be too much of a burden but which config file should I put toneduration in as most of the config files have warnings in them stating not to edit them manually.

That would depend on how you manage dahdi, traditionally in /etc/asterisk/chan_dahdi.conf for the channels you want to set it on. But I think the FreePBX dahdi module might do that differently

Okay, Looks like it is in /etc/asterisk/chan_dahdi.conf. I will try adjusting that and see if it helps. Thanks so much for your help.