[asterisk-users] DTMF not being heard correctly by far end conference system

[James Lamanna]

Hi Duncan,

On Wed, Jan 12, 2011 at 10:13 AM, Duncan Turnbull <duncan at e-simple.co.nz> wrote:
> Hi Thorsten
>
> Thanks very much, at this point my preference is rfc2833 but I will try some other options.
>
> The system is generating audible tones (that I can hear), although I think the audio is generated by the last sip device in the network so if thats so I don't have any control of it. Probably then I have to go to inband to get some control back, I am not sure what I lose from this, or change upstream provider (although the current provider works from a different system)

In my DTMF experience I have found a few IVRs and conference systems
out there that won't accept my DTMF, even though its DTMF that I can
see going out over PRI channels. My guess is that these systems use
too tight of a duration window on their DTMF detectors. In your case
I'm guessing that for some reason the SIP DTMF tones are coming out
with too short of a duration.
I believe you can fiddle with the dtmf tone duration and spacing in
channel.c but I don't know if that will fix the issue.
Is it possible to get the DTMF specs from the manufacturer of the
conference system?

-- James