I am doing a project on GSM.. In that i want to detect the key pressed at the other side on active call.... I am trying with a dtmf decoder circuit at speaker output but it is not working...Plz if any one has any other idea or solution plz reply...........
if you make it like the above? if so .... check Keytone volume on your mobile GSM because if a small volume will not work, should Keytone maximum volume