DTMF talk-off a real fix?

Ok so we are running Asterisk 1.4 . We are experiencing random DTMF Talf off. This is where Asterisk interprets voice as DTMF as regenerates it as DTMF tones. You may think that the person on the other end of the call hit a button or the redial button. We have relaxdtmf=no. We also have DTMFMODE set to rfc2833 in sip.conf.

Does any one out there know of a real fix or tweaks for this problem?

How often does this happen. The only absolute way of preventing it, if you have features enabled, is at the originating phone, and it is not a phone feature I have heard of.

If you have DTMFMODE set to RFC2833, then it is something upstream of Asterisk that is interpreting the voice as DTMF.

This is not an “upstream” issue this IS an known Asterisk problem. We have deployed 1000s of endpoints(multiple manufactures) with Asterisk with every carrier out there with analog, PRI, T1 and Dynamic PRI. They all experience this issue occasionally. We had some suggest changing DTMFMODE to inband. We are currently testing this.


Again, you need to define “occasionally”. Unless the upstream actually filters out the DTMF frequencies, which will distort the voice, occasionally you will get talk off; that’s an intrinsic flaw in short duration in band signalling.

The question is whether it is happening a lot more often than would be normal.

There have been issues reported that Asterisk sometimes turns on in band detection, even when set to RFC 2833, but, apart from that, if the upstream is RFC 2833, the only way that Asterisk will react to DTMF is if the upstream has detected it and encoded it into RFC 2833. If you might be affected by one of the issues, you need to look at the issue tracker to see whether and in which versions, it is fixed.