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Understanding ISDN and the ISU 128
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 telephone wire.
ISDN provides a means of integrating these services and modernizing com-
munication networks for information movement and management efficiency.
THE ADTRAN ISU 128
The ADTRAN ISU™ 128 is a stand-alone device that connects data terminal
equipment (DTE) to the ISDN network or to a leased digital network for data
transmission. The ISU 128 allows high-speed data transmission (up to 128
kbps) over a single ISDN line. The ISU 128 meets the Microsoft Windows
Plug-an-Play specifications. The file MDMADTN.INF is required. To obtain
this file contact our website at URL of www.adtran.com ADTRAN technical
support. The number is located on the inside back cover of this manual.
From the network, ISDN is delivered by a single 2-wire 2B1Q U-interface
which is connected directly to the ISU 128. ISDN network termination is de-
signed into the ISU 128, eliminating the need and expense of a separate NT1.
For network testing, the ISU 128 responds to NT1 test commands from the tele-
phone company central office (CO).
The ISU 128 transmits data over an RS-530, V.35 interface, or EIA-232 interface,
selectable on the front panel. The ISU 128 performs at synchronous data trans-
fer rates of 2400 bps to 128 kbps and asynchronous rates of 300 bps to 115.2
kbps. For speeds over 64 kbps, the industry standard BONDING or MULTI-
LINK PPP protocol aggregates the two 64 kbps B channels for a maximum of
128 kbps. The ISU 128 is intended to support the transfer of data and images
61202.029L2-1
ISU 128 User Manual
Chapter 1
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