Hi, I would like to test adding the following header to the 100 Trying and 200 OK messages: Allow-Events: telephone-event This is to try and interoperate with Cisco equipment that behaves this way. As it stands, perhaps as a result of not sending this header from our FreeSWITCH box, the Cisco is not offering RFC 2833 in the SIP ACK and therefore DTMF does not work (as they don't support SIP INFO). Is there any way of doing this in FreeSWITCH? Many thanks. Kind regards, SebA