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1 INTRODUCTION
MDS921AE-10BT, MDS920C-10BT and MDS922AE-10BT network and line termination units are
a part of the Black Box PAM family (hereafter family) constructed for the organization of high-
speed communication channels over one pair copper lines (DSL).
This family of units represents G.shdsl modems that have 64 – 2312-kbit/s speed of data transfer.
The modern type of TC-PAM encoding has the best characteristics of long-distance data
transmission and electromagnetic compatibility while working over one pair subscriber lines. TC-
PAM can be deciphered as Trellis Coded Pulse Amplitude Modulation. The essence of this
encoding method consists of an increase of layer numbers (encoding states) from 4 (as in 2B1Q)
to 16 and use of a special error-correction mechanism.
This family of modems with different network interfaces (G.703, Nx64 (V.35/V.36/X.21) and
Ethernet 10Base-T) can be used as transfer systems between multiplexers, routers and cross-
connection devices in different networks, for example:
1. for the organization of E1 (2048 Kbit/s) channels between Public automatic branch
exchange (PABX), Digital Loop Carrier systems, TDM multiplexing and terminal stations
of mobile networks as well as their connection to SDH networks;
2. for the organization of high-speed communication channels (data links) in data transfer
networks and connection of Internet-providers’ access nodes;
3. for the connection of remote working stations (computers) and small Ethernet branches to
the office computer network and for integration of IP and IPX network segments, for
providing Internet access, etc.
The Ethernet 10BaseT interface allows an operator to provide services for the interconnection of
territorially distributed local networks, to provide high-speed access to Internet and to use
MDS921AE-10BT, MDS920C-10BT and MDS922AE-10BT devices in applications that require
high speed data transmission.
The use of ATM technology makes it possible to connect MDS921AE-10BT, MDS920C-10BT and
MDS922AE-10BT units to DSLAM devices of different manufacturers.
The units of this family, subdivided into network termination (NTU) and line termination units
(LTU), can be installed at the customer (user) premises and at the operator (provider) nodes,
respectively. NTU–NTU connections (for instance for the connection of two local networks) or
LTU–LTU connections (for the connection of large nodes) can be used to organize “point-to-
point” connection.
It is possible to power units locally with 48 V
DC
(telephone station batteries) and with 220 V
AC
.
This family of devices has three mechanic designs:
1. Sub-Rack (MDS920C-10BT) is a unit to be mounted in 19’’ chassis (MDS920AE-RMDC)
2. Mini-Rack (MDS922AE-10BT) is a unit of 1U height (44.5 mm) to be mounted in 19’’ rack
cabinet;
3. Stand Alone (MDS921AE-10BT) is a compact unit to be mounted on the tabletop/desktop
or another horizontal surface.
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