DTMF Tone Question

As far as I know the only options for DTMF with the 1.2.2.19 firmware are under the "Account" settings tabs. Here you can change the type of DTMF the phone uses on each account. The options available are "in-audio", "via RTP (RFC2833)" and "via SIP INFO". You can have the phone set to use more than 1 DTMF method at a time and from my experience this can cause issues depending on your carrier and the PBX at the other end.

Under the "Advanced Settings" tab you have an option for "DTMF Payload Type" which can effect the out of band DTMF transmission. The default is 101 and I don't know if changing this would help so you might need to do some research before adjusting it.

Below is a great explanation of how DTMF works which can be found here http://www.velocityreviews.com/forums/t234030-dtmf.html

1) In band digits: digits are passed along with the rest of your voice,
using the same VoIP codec as your voice (G.711, G.729, etc.)

2) Out of band digits using special IP pakets that are sent along with
the voice path. These packets use RFC 2833 format, these packets must
have a "payload type" that matches what the other end is listening for.
Cisco often defaults to 101 for this payload type, which uses your
definition to negotiate (again via H323 or SIP) with the other end
during call establishment. These digits are pulled out of the voice
stream and sent only in the RFC 2833 packets.

3) Out of band digits sent via the signaling layer (UII packets).
These have no payload type defined. The digit is removed from the
voice path and signaling messages are sent to tell the other end about
the digits.

In 2 & 3, when the other end receives these special packets that
represent digit value & duration, it will regenerate the proper tone
and duration back to the voice path.

The purpose of this is to guarantee a valid tone detection at the
distant end of the call, since some voice codecs may not be able to do
that properly (other then G.711 it's a gamble).

Regards,