It appears that we cannot use carrier's RFC2833 sequence as it's missing up to 50% of digits sent to them by the original caller. And this is not happening on the same system with 2 other carriers. Peter and Michael, thank you very much for your help and explanations. WBR / Mike ----- Original Message ----- From: Michael Collins Sent: 07/19/12 01:32 AM To: FreeSWITCH Users Help Subject: Re: [Freeswitch-users] DTMF detection in the core & spandsp On Wed, Jul 18, 2012 at 3:27 PM, Mi Ke < mi.ke@null.net > wrote: So in order to use just spandsp I need either to disable RFC2833 detection at my side or to ask originating party to disable sending us RFC2833 and just send us audio intact - have I got your point ? That's kinda sorta what he's saying. A better way of saying it is this: if your carrier sends you RFC2833 DTMFs then you don't even need to turn on dtmf detect stuff. Unless there is a compelling reason to go in-band I'd say just use RFC2833 and be done with it. -MC