I am using asterisk for making outbound PSTN calls. We are using BSNL PRI Line, and dahdi. Recently we are facing some problems with the call hang ups, actually we have 30 channels but when we use more than 15 channels some calls are abnormally terminating, so I just want to know any agi method where we can retrieve the reason for the call hang up i.e by the network, user or system fault etc. Please suggest me any software or hardware changes to improve system capability to handle 30 calls, Software upgrading or LAN cable issues etc, I am ready to make any changes, Please help me..