DTMF Detection

I am having TDM4XX running 4 FXO ports, and wish to connect to existing PBX for IVR application. Now, can I know how to make the Digium TDM card to receive any DTMF signal from my PBX POTS? such as Busy DTMF signal, No Answer Signal…???
Please some one advice on this. I will say that PBX side got no issues, I did program PBX to generated the DTMF.