[Asterisk-Users] Sending DTMF to PSTN problem with SIP

[Eric Wieling aka ManxPower]

CClarke wrote:
> Dear All ~
> 
> I have * setup & running ok (with two Wildcard X100P's to PSTN). I also have
> two analog phones connected into same through a SIPURA 2000. These work fine,
> except that when I call out through PSTN & try to send DTMF tones to (say) a
> remote PBX to dial an extension, the gain seems to go wild (high), and the
> DTMF tones are not recognized at the other end.
> 
> I tried setting the SIP2000 to use inband dtmfmode (as opposed to auto), and
> likewise in sip.conf, but no success.
> 
> btw, I've also set relaxdtmf=yes in zapata.conf since inbound calls sometimes
> seem to have trouble dialling extensions.
> 
> A soft IAX phone (e.g. DIAXPhone) works ok, so I suspect my SIP2000/sip.conf
> setup, but can't see what I'm doing wrong.

You can only use inband DTMF when using the ulaw or alaw codec.  If you 
use any other codec you need to use Out of Band DTMF, i.e. INFO or 
RFC2833.  This is not an Asterisk issue.  Codecs discort DTMF.  Both 
Asterisk and the phone should be set to the same DTMF mode.