Operating the DSU
If the tributary DSU is to initiate the call, set the control for Cllbk and the tributary for Pswrd.
External DBU Option Set (This option set will not appear if a DBM is installed.):
•ExtBU ± Select whether the external DBU will answer or place backup calls. The external DBU must be able to support Dial on DTR.
Ansr ± The external DBU will answer incoming calls. The DBU must provide DSR when the call is complete.
Orig ± The external DBU will place an outgoing call.
None ± The external backup feature is disabled. The DSU will not switch data to the alternate port. (None is the default.)
Backup Option Set (None of these need to be set for manual backup.):
•Auto Bckup ± Select Enab.
When enabled, the DSU will automatically initiate dial backup. Up to 10 attempts will be made.
If both the control and tributary DSUs are configured for automatic backup, NtwkTimOut should be set to different values so that the control and tributary DSUs do not try to place a call at the same time.
On a
•Bckup Dir ± Select the call directory identifier
(1 to 10) stored in the DBM's Backup Directory for the telephone number to be dialed.
•AutoRestor ± Select Enab.
When enabled, the DBM or external DBU automatically restores data to the DDS circuit when service is restored and the amount of time set in RestoreTimOut has expired.
•NtwkTimOut ± Set the amount of time that the DDS circuit must be out of service before a backup attempt is made: from 0:00 (minutes:seconds) to 29:59 (the default is 0:20).
•RestorTimOut ± Set the amount of time that the DDS circuit must be back in service before automatic restoration is attempted: from 1 to 60 minutes (the default is 5 minutes).
•TriesTimeOut ± Specify the overall time limit during which a DBM will automatically attempt to establish a dial backup call: from 1 to 60 minutes (the default is 15 minutes). Auto Bckup must be enabled.
•MultiCall ± Select Enab.
When enabled, instead of following the normal calling cycle, the DBM cycles through all dial strings contained in its Backup Directory until a call attempt is successful.
Do not enable MultiCall unless more than one telephone number is in the Backup Directory and each successive (i.e., 1, 2, 3, etc.) telephone number is different from the previous entry. Directory entries should be unique.
Understanding Operating Modes
When a DSU is equipped with a DBM or an external DBU, the Backup branch controls operation of the Dial Backup function. The DBM has four modes of operation:
•In Idle mode, there is no dialed connection. The DDS circuit is active and carrying user data and diagnostics.
•In Standby mode, the unit has a dialed connection to another DBM or compatible dial backup unit, but the DDS circuit is still active and carrying user data. The dialed digital circuit carries diagnostic traffic addressed to either the tributary DSU or DBM. These diagnostics do not disrupt the DDS circuit.
•In Dial Backup mode, the dialed circuit is active and carrying user data and diagnostics.
•In External Backup mode, the external DBU is the DSU's alternate connection with the remote device. Depending upon how the DSU is configured, the external DBU will either establish the dialed connection (ExtBU set to Orig) or respond to an incoming call (ExtBU set to Ansr). Once the dialed connection is established, the DSU switches data and diagnostics to the dialed link, then drops backup when service is restored.
Table
December 1996 |
