Problems with DTMF - door phones use RFC2833, provider uses inband

[George Ts]

Hello,
Ever since we migrated to 3cx we are having issues with DTMF.
Our door phone is using RFC2833 in order to accept incoming DTMFs, so that local extensions can open the door by pressing a DTMF sequence.
However, our provider is using inband.
We have thus configured our local extensions to use inband, in order to be able to handle our customer's IVRs when they make outbound calls to PSTN, thus when using our SIP provider.
However, our local extensions can no longer open our local doorphone.
As far as I know,3cx only supports DTMF relay, i.e. it relays the DTMFs as received by the extension. It does not support DTMF interworking, i.e. translating from RFC2833 to inband and vice versa.
Since our provider uses a different method than our door phone, what is the solution we could have in our environment so that both can work?

Thank you in advance,
George

 

[JohnS_3CX]

Hi George,

Can you please tell me what version your 3CX system is?

 

[George Ts]

Hi @JohnS_3CX
We are running 16.0.8.9, Enterprise License.
It would be great if 3cx could support DTMF interworking and a different DTMF method per SIP trunk, but i guess this is to be written in the Ideas section.

 

[JohnS_3CX]

There are some upcoming changes in V18 that will address a lot of these issues when the provider does not support RFC2833.

The internal phones will be able to use RFC2833 and the DTMF will be converted to in-band once it goes to/from the provider. This should address the problem you are currently facing with your provider who only uses in-band.

 

[leejor]

I've seen some devices (sets/ATAs) that allow you to set the DTMF Method as "Auto", to accomodate most situations. I don't suppose your sets have that option to try.

On second thought...the 3CX selection first encountered, may remain for te duration of the call.

 

[George Ts]

Thanks @leejor !
The door phone actually supports Auto, it just does not work. It is a Fanvil i20s, I contacted Fanvil and they said that the door phone only interprets incoming DTMF if they are either in SIP INFO or in RFC2833 format. The auto and the inband choices are just for outbound DTMF. Looking forward to 3cx's implementation i v18. When is it expected by the way?