Dtmf problem

Hi to everyone,
I’ve this problem, the pbx doesn’t recognize the DTMF tone, I explain.

Usually my plant are composed both of Deskphone (SNOM, Yealink, Cisco, Fanvil) and cordless (Gigabit), Gateway (when the line are PSTN) Sangoma or Patton and for the Analogic devices I use Grandstream from 1 to 32 ports.

Till now, and we’re talking at least of 60-70 installation I’ve never touched the DTMF configuration, ever without problems.

In the last plant I’m using FreePBX 16.0.40.10 (last module update made today), a couple of Snom Deskphone, about 15 Gigaset cordless with N510 IP, a Patton 4634 for the lines, well what happen is that FreePBX doesn’t recognize the DTMF tone, both using the PSTN lines (so by the Patton) and between Extensions so without use the Patton.

On every device like on the PBX the DTMF configuration is set on RFC2833, does anyone has idea to what look for to solve ??

A little upgrade, I’ve toke a pcap file and the RTP report show the DTMF tones produced by the phones.

Thanks a lot in advance
Enrico

If you are using RFC2833 (same applies to the RFC 4733, with the current SIP driver), there are no tones involved, as far as Asterisk is concerned, as the digits are sent as the actual digit.

You need to start by enabling DTMF logging, to see what is being received as digits, then progress, to RTP logging, or capturing the RTP with something like wireshark (or tcpdump followed by wireshark), to confirm that RFC 2833 really is being used and the correct telephony events are being sent.

Hi David, thanks for your answer, I’ve already captured RTP with tcpdump and checkes with Wireshark and yes, the tones are DTMF on codec G711

dtmfmode needs to be inband, for those tones to be recognized. (I’m not sure if automatic will work.) RFC2833 digits are sent with a different payload type, telephone events, typically 101. Generally, though, it is better to get the other side to use telephone eents.

Hi David,
thanks, I’ll try to modify the configuration before tomorrow EOD and I’ll answer about the results.

Thank you

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