I have been using a Cisco 2901 router with FXO cards and a TCL script to detect DTMF digits for a while now. Since the EOL has been set for these routers, I decided to try the replacement router (the 4331) with NIM cards. However, I'm having some issues detecting DTMF digits with the new router setup.
We register SIP extensions to the router using CME. These SIP extensions then solely route calls to / from the FXO ports. IE - no sip to sip call or FXO to FXO calls. We only detect DTMF digits on the SIP side of the call (we don't care about any DTMF digits detected on the FXO physical port). This all worked great on the 2901 router.
On the 4331 router, all the SIP configurations work, we can place inbound and outbound calls, but the TCL script will not detect DTMF digits on the SIP side of the call. I have "puts" statements in the script, so I know it's actually running correctly, and I get the DTMF timeout T. If I switch the script to setup DTMF detection on the opposite part of the leg (detect on the FXO port), it detects the DTMF properly. I've sent the DTMF on the SIP side as RFC2833 and as in-band tones (neither gets detected). I believe the router is correctly interpreting the RFC2833 events, as the DTMF digits are getting converted and sent out the FXO port properly.
Is there something the new router requires to setup DTMF detection on the voip leg? There is a PVDM4-32 module on the motherboard of the router.
Thank you for any guidance / suggestions.