Specifications

33
CHAPTER 4: Applications
4.2 Dial-Backup Application
The CSU/DSU MS DBU provides point-to-point connection to the network.
With one of the DBU module cards installed, the unit is capable of dial backup,
allowing the unit to dial around a failed network. See Figure 4-3.
With the DBU options, you can configure the unit to:
• Enter DBU under specific primary network conditions.
• Lock out DBU over the weekend and/or at specified times of the day.
• Dial a specified number when a DBU activation condition is detected.
Figure 4-3. Dial-Backup Application.
E NTERING D IAL -B ACKUP M ODE
When a condition for entering dial-backup mode is detected, the Alarm LED turns
on and the buzzer sounds. The buzzer alternates between 30 seconds on and 30
seconds off unless the DDS line is restored or unless it is disabled by using the
Quick key and selecting Turn Off Beep. See Figure 3-1 in Chapter 3 for more
information on the Quick key.
DDS
Switched
Network
V.34, ISDN, 4-Wire,
Switched 56
CSU/DSU MS DBUCSU/DSU MS DBU
DTE DeviceDTE Device