Dial Backup Operation - ADTRAN Express 5210 User Manual

Chapter 1. Introduction

Dial Backup Operation

The Express 5210 supports dial backup of point-to-point DDS
circuits or frame relay circuits. For DDS backup, the Express 5210
enters dial backup based on physical line faults. During dial
backup, the Express 5210 monitors the main line integrity and
drops the dial backup call when the main line is restored.
For frame relay dial backup, the Express 5210 monitors the physical
line condition as well as the signaling state of the frame relay
circuit. Once the configured DBU criteria have been met, the
Express 5210 initiates a DBU call. The Express 5210 receiving the
call qualifies the incoming call and re-routes the PVCs affected by
the outage while continuing to service other PVCs on the network
interface.
During dial backup, the Express 5210 constantly monitors the
physical state of the network. It also attempts to re-establish
signaling on the main line. Once both the physical integrity and the
signaling state are restored, the unit drops the dial backup call and
reverts to the main line.
The 4-wire SW56 DBU card is compatible with AT&T Accunet and
Sprint SW56 type services. The V.34 DBU card allows switched
backup over the public switched telephone network (PSTN). The
ISDN 1B+D card supports a U-interface to the Basic Rate ISDN and
is compatible with National ISDN and AT&T DMS.
The Express 5210's unique DBU cards are field-installable by the
customer. See the section DBU and Voice Interface Card Slots on page
2-4 for information on installing DBU cards. Also see the chapter
Dial Backup Configuration on page 10-1 for information on
configuring DBU options.
The backup options are described in the following section. Contact
the local telco provider to determine which services are available in
your area.
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