ADTRAN Express 5210, User Manual

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Chapter 1. Introduction
61200208L1-1 Express 5210 User Manual 1-7
DBU Card Option Descriptions
4-Wire Switched 56 DBU Card
This dial-up 4-wire SW56 card allows you to pay for data
connection only for the time the unit is active. The regional
operating companies provide the 4-wire local loop service to SW56
customers.
V.34 DBU Card
This module backs up the leased line application at data rates up to
33.6 kbps over an ordinary telephone network.
ISDN DBU Card
1B+D Basic Rate ISDN service provides backup over a switched
56/64 kbps circuit.
DCE Card
This module connects an external DCE device to the Express 5210.
The card can act either as a dial backup interface or as an alternate
network interface (supporting access rates up to 512 kbps).