be met before it CNG fax detection will be checked.. 1. The peer has to be using inband DTMF (makes sense as you have to attach a DSP to the channel to detect DTMF) 2. T.38 has to be enabled.. If my read is accurate, then that means that it is not possible to do CNG detection on SIP connections using RFC-2833 until after the channel has been answered and a DSP is attached to it. Anyone care to comment?