The Dial Backup capability of the TSU ESP allows for automatic switched backup in the event of a dedicated T1 line failure. The Dial Backup is accomplished through a family of plug-in ESP DBU cards.
This is the External DCE DBU card. When a failure condition occurs on the T1/FT1, the DBU card utilizes the switched network DTR dialing (External DCE) to initiate a call to the remote end. The user can choose whether the unit automatically or manually reverts to the dedicated circuit when it is restored. Optional Weekend and Time of Day Dial Backup lockout options are provided in the TSU ESP DBU option menu.