Need help with a DTMF problem

[Martin_Thomas_HPA]

Hello i have a special issue with a RITAS Alarming device. If i call the Device from 3cx it accepts DTMF RTP-Events and everything is ok. If the Device call to 3cx, 3cx does not forward the RTP-Events (DTMF) to the RITAS Device. What i have seen is that the RITAS device don't offer any SDP information's in both directions. On an Call to the RITAS device it seems that 3cx forces RFC2833. When RITAS initiate the Call with no SDP it seems that 3cx send nothing. Not RFC2833, not In-Band. Can i force RFC2833 for Devices that don't offer SDP. Have anyone other ideas for me?

 

[Martin_Thomas_HPA]

After a while reading the traces i have found one difference. In the bad case the source Phone send a zero volume in the DTMF RTP packet. Is that the reason why 3cx do not forward the Packet to the receiving device?