61202.086L1-1
ISU 512 User Manual
1
Chapter 1
Understanding ISDN and the ISU 512
ISDN OVERVIEW
The Integrated Services Digital Network (ISDN) is a public or private switched
digital network. ISDN is an international standard for digital communica-
tions, allowing a full range of enhanced services supporting voice, data, and
image applications through standard interfaces over a single pair of telephone
wires. ISDN provides a means of integrating these services and modernizing
communication networks for information movement and management effi-
ciency.
PRODUCT OVERVIEW
The ADTRAN ISDN Service Unit (ISU
™
) 512 is a stand alone device that con-
nects data terminal equipment (DTE) to the ISDN network or to a leased digi-
tal network for data transmission. The ISU 512 is a basic inverse multiplexer
that provides cost-effective high-speed data transmission for a single applica-
tion at rates up to 512 kbps.
From the network, ISDN is delivered by up to four 2-wire 2B1Q ISDN Basic
Rate U-interfaces which connect directly to the ISU 512 (U interface). ISDN
network termination is designed into the ISU 512, eliminating the need for sep-
arate NT1s. For network testing, the ISU 512 responds to NT1 test commands
from the telephone company central office (CO). The ISU 512 (ST interface) is
designed to work with the 4-wire AMI signals provided by an NT1.
