Gamma supports the transmission of digits as RFC2833 events, as well as in-band DTMF transmission (G711alaw is the preferred method, detection of tones with G729 is not guaranteed).
DTMF events must be sent either in-band or in accordance with RFC2833 (payload 101). Gamma does not support the conveying of digits in SIP INFO, and will return a ‘415 unsupported’ error upon receipt of an INFO message.
If DTMF is not working with one particular number then you should ensure that the ‘event duration threshold’ in your RFC2833 events contains a positive value, and one which increments with each individual packet of a DTMF tone. An ‘event duration’ set to zero can cause DTMF events (particularly the initial digit) not to be recognised as a valid input by particularly sensitive far-end IVRs. Similarly, the codec sampling rate should be set to 8000 KHz. It is always a good idea to try to emulate the problem by dialling the affected IVR from other providers’ networks.
