DTMF Signals Not Detected

[aidanm]

Hi everyone,

I'm currently using 3CX (Version 20.0 Update 5) and have a SIP trunk set up to Twilio. The call routing works fine, but I'm running into an issue where DTMF signals are not being detected on the 3CX side.
From my research, it seems that Twilio expects DTMF to be sent using RFC-2833 (RTP events), but I haven’t been able to locate the setting in the 3CX management console to explicitly enable or configure this.

If anyone has experience with this setup or knows where to confirm or force RFC-2833 in 3CX, I’d really appreciate your guidance.
Thanks in advance!

 

[edossantos_sipcaller]

If a 3CX IVR / Digital Receptionist / CFD app can't detect DTMF tones, most probably those are being sent as audio in-band. You can confirm this with a Wireshark capture. There's nothing to configure on the 3CX side, the SIP Trunk should send tones as RTP signals, otherwise the audio compression might cause that tones are not reliably detected.

 

[K_SAK]

a SIP trunk set up to Twilio.

Is this on the standard Twilio template, automatic setup?

 

[aidanm]

@K_SAK, yes

 

[K_SAK]

Can you try calling your number from another source? It could be that where the call originates has an issue sending the DTMF properly.