DTMF over SIP trunk

[TechInter]

My problem is on 3300 MCD4.0. I use a SIP provider for my outbound call and I don't know why but on several number (20%) that a auto-attendant anwsers, I'm unable to cut the voice to dial a extension. If I place during communication DTMF sound through the handset, it works!

I tried to record an X-lite on the account and I don't have that problem.

Suggestion ?

Thanks

 

[IrwinMFletcher]

So IP set, out SIP trunk? You need to look at the SIP negotiation and see what they are setting for RFC 4733 indication.

But here's a question. If you call out your SIP trunk to someone's cell phone, and you press a dtmf key on the IP set, does the cell phone user hear it? If that is the case, and the calls are being setup the same way to an external auto-attendant, then the problem is with the SIP SP. The reason being that it's up to the IP->TDM transition point to re-create a detectable TDM tone. If you can hear it on the cell phone, then they are getting the RFC indication, they just are not creating a tone capable of being detected.