I have a IVR system which is causing me some difficulties and am after some help to see if it is the source of the problems or just a victim of the cause. The system is running windows 2K and it uses the the CAPI interface to receive calls through a FRITZ ISDN card. Now the trouble I have is with DTMF recognition when the caller is in noisy environments. If the noise exceeds a certain (as yet unknown) threshold then the system is not responding to DTMF. Now my question is the following: The users are all using Nokia GSM hand sets. As my limited knowledge recalls GSM sends the DTMF as signaling data and the ISDN should receive the DTMF without requiring operation of the audio channel. Am I correct? If I am correct why do I have this problem; Is it due to the nokia trying to turn the complex noise into DTMF and overriding the keyboard input? Is it due to the CAPI software (at the server) getting audio channel and trying to get DTMF out of that and thus overriding DTMF from phone keyboard (If so I thought that the GSM used lower quality codec so how is DTMF arriving via audio channel?) This all leads me to the situation of if it is the CAPI end that is causing me the problem maybe I can use asterisk and prevent audio channel DTMF collection (is this simple) but if it is elsewhere what can I do? (change handsets?) Thanks for any insight on this Regards Chris Lee