Because it is a proprietary solution, it may need to go back to their developers. The code 16 is defined by ITU as a Normal Call Clearing. Now why a device may issue it is dependant on how the device was created to interpret this. Like I mentioned previously, in a Quintum it is used whenever the caller hangs up the call prior to the Quintum reporting that it is connected. Now if you look at the actual event log, you will see that, per the H.323 spec, cause 16 is used anytime a call is disconnected normally by one party or the other, but the quintum only reports it to the CDR if the even happened prior to the call being answered.