Dear Experts ,
I have one general question (for DTMF detection) that makes me crazy . if inbound call (GSM >>to>>IVR). Normally , DTMF tone (from the external GSM phone) should be received by the IVR , and it will make FFT to extract 2 basic frequencies , then the keypad pressed is know.
What about in-Band DTMF, where there is no tone sent to IVR . How does the IVR recognize it ?.
Thanks,
Waleed