The isdnCallHistoryTable contains information pertaining to the last 20 ISDN calls made, since the last system startup. Each call that appears in the isdnCallTable, will have its information stored here (temporarily), once it disconnects. Creating entries: Entries are added by the system once a call is disconnected. Deleting entries: Entries are removed by the system. The table is designed as a circular queue (or FIFO); the most calls are stored at inx 19 with older calls rolling off the top of the table at inx 00.