How to fix Interrups?

When i get a call to me pbx system, the IVR answer but if the client hangup, the pbx detect the hangup 10 seconds after the client already hangup the line.

I think that delay is not in the asterisk source,config,etc. I think that problem can be with the system interrups with the PCI that manage the hadware that manage the POST lines.
How to fix that?
The same will happen using T1 cards ?(T1 are digital cards NOT analog)