1-13550-A2-GB20-20 December 1996
About Your DSU
Overview 1-1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Standard Features 1-1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Optional Features 1-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
V.32 DBM 1-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2-Port TDM/Flex 1-3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Upgrades Available 1-3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Technical Specifications 1-3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Equipment Warranty and Support 1-8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Overview
The Model 3550 or 3551 data service unit (DSU)
supports communication between computers and other
data processing devices by providing connections to
digital data service (DDS) transmission facilities. Both
point-to-point and multipoint configurations are
supported.
The following sections describe the standard features
of the DSU, as well as the features of the options that may
have been ordered with your unit. The technical
specifications of the DSU and its orderable options are
near the end of the chapter.

Standard Features

The Model 3550 or 3551 DSU offers the following
features:
•Multispeed operation. The DSU operates at data
rates of 2.4, 4.8, 9.6, 19.2, 38.4, and 56 kbps
full-duplex over the digital data service (DDS)
network.
Two DTE connectors (interfaces) are provided for
Port 1: EIA-232-D
and
V.35. Use the EIA-232-D
connector for data rates up to and including
19.2 kbps; use the V
.35 connector for higher rates.
•Rate Adaption.
W
ith this feature, the DSU can
adapt its data rate to a low-speed application while
operating over the high-speed DDS circuit.
•LADS operation.
The DSU can operate as a local
area data set (LADS) (sometimes called a
limited-distance modem, or LDM) at 2.4, 4.8, 9.6,
19.2, 38.4, 56, or 64 kbps.
•Single-Port Async/Sync. The single-port
asynchronous-to-synchronous feature makes it
possible to send asynchronous data over the
synchronous network.
•Nondisruptive Diagnostics.
When set up to use
nondisruptive diagnostics, the DSU sends
diagnostic data without interrupting or disrupting
customer data.
•NMS control. The DSU can be controlled by
COMSPHEREr6700 Series NMS. The 6700
Series NMS operates using Advanced Diagnostic
protocol (ADp).
The Model 3550 DSU requires a hubbing device
for connection to the NMS; the Model 3551 DSU is
connected to the NMS through the shared
diagnostic unit (SDU) in the COMSPHERE
3000 Series Carrier.
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