Nortel Networks NN43001-301 User Manual
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ISDN Primary Rate Interface equipment overview
Echo canceller interface
Echo cancellers are required only on satellite transmission circuits. The
echo canceller detects the length of the loop, and then cancels out reflected
transmission. (Callers will not hear echoes of their own voices reflecting
back to them from the far end of the call.)
The echo canceller’s control protocol must conform with that of the Tellabs
Model 251. Both the echo canceller and the PRI circuit card act as Data
Terminal Equipment (DTE).
QMT21 High Speed Data Module
The QMT21 High Speed Data Module supports the 64K Clear Data feature.
(It allows data terminating equipment (DTE) to send and receive 64-Kb/s
clear data.) The QMT21B is required for Large System to Large System
configurations.
QPC720 PRI for 1.5/2.0 Mb gateway
Systems which are being used as a 1.5/2.0 Mb Gateway, one or more
QPC720 (1.5 Mb) Primary Rate Interface circuit cards will also be needed.
Note: Older vintages of the QPC720 PRI cannot be used for Gateway
applications. The 1.5/2.0 Mb Gateway feature requires the use of a
QPC720 circuit card with firmware updated to provide modified PAD
values.
Clock operation for the NT8D72
There are two types of clock operation—tracking mode and free-run mode.
Tracking mode
In tracking mode, the PRI loop supplies an external clock reference to a
clock controller. Two PRI loops can operate in tracking mode, with one
defined as the primary reference source for clock synchronization, the other
defined as the secondary reference source. The secondary reference acts
as a back-up to the primary reference.
As shown in
Figure 6 "Clock controller primary and secondary tracking"
, a system with dual CPUs can have two clock controllers (CC-0
and CC-1). One clock controller acts as a back-up to the other. The clock
controllers should be completely locked to the reference clock.
Nortel Communication Server 1000
ISDN Primary Rate Interface Installation and Commissioning
NN43001-301
02.03
Standard
Release 5.5
7 December 2007
Copyright © 2003-2007, Nortel Networks
.