I have asterisk 1.4.26 running via astlinux with a Sangoma a200 board (2x FXO + 2x FXS) and Grandstream GXP2000 phones. We have noticed some instances where DTMF tones are not recognized by remote systems. Specifically we have this problem with a particular conference call service keying in the PIN (says its not recognized) and even with an IVR used to claim unemployment benefits (won’t recognize keyed in SSN). In both cases, we can accomplish these calls using a cell phone. All the calls are run through an FXO port on the Sangoma card. These are the only two instances that we are aware of where we have the problem; DTMF seems to be recognized OK by other remote systems.
At this point, I’m not sure if this is a configuration issue with asterisk, sangoma, and/or grandstream. Any suggestions on a strategy to attack this problem would be greatly appreciated.