Question : CME incoming external call problem

the problem is with the incoming call from FXO, if the outside user stop calling the phone number after only two rings the CME still holds the call and keep ring even thought the caller has hung up!
is there any way to force CME to disconnect the call if the caller stop has call,  
I have got CME in cisco router 2600 Version 12.4-12.
any help please!

Answer : CME incoming external call problem

the frequency is 395 and cadence is 0.28 0.28 0.28 0.28
apply it under the voice-port

Hussam