01/01/01 08:07 Overview 1-1
Chapter 1
Introduction
1.1 Overview
General
HCD-E1 is a standalone HDSL NTU (Network Terminal Unit) / LTU (Line
Terminal Unit) that provides the user with one E1 sublink drop & insert
port and two n × 64 kbps or n × 56 kbps data channels. Fractional E1 from
the E1 sublink, as well as data from the n × 64 kbps / n × 56 kbps channels
are multiplexed over E1 frames and transferred by the HDSL modem to the
remote location. For direct connection to DACS, RAD’s HCD-E1 unit can
be used in the central office, eliminating the need to convert back to
n × 64 kbps.
HCD-E1 supports the transmission of two synchronous data channels and
one E1 sublink, over the HDSL link. The sublink enables the connection of
fractional E1 equipment (digital PBXs), thus enabling HCD-E1 to serve as an
integrating multiplexer for E1 and fractional E1 services.
The mapping of the user’s data to the main link time slots is user-selectable.
For the synchronous data ports and E1 sublink, three mapping methods are
available: bundling into consecutive or alternate time slots, or placing in
individually selected time slots. A sublink time slot is always routed to the
main link time slot with the same number.
In addition, HCD-E1 can also be operated in an unframed mode: in this
mode HCD-E1 accepts a 2048 kbps data stream through the E1 sublink or
data channel and converts it to an unframed G.703 signal for transport over
the HDSL link. Thus, HCD-E1 can also serve as an interface converter and
high-speed, short-distance modem.
HCD-E1 can work with an HDSL repeater (H-RPT) on the main link.
HCD-E1 can check the H-RPT alarm messages and connect/disconnect the
local loopback on H-RPT (LOOP L HRPT).
Versions
HCD-E1 can be ordered in several versions, which differ in the number
and type of user ports:
•
One or two synchronous data channels. The data channels can be
ordered with RS-530, V.35, V.36/RS-449, or X.21 interfaces.
•
One synchronous data channel (with RS-530, V.35, V.36/RS-449, or X.21
interface) and one Ethernet interface module (IR-ETH, IR-ETH/Q, or
IR-IP).
