Nortel Networks NN43001-301 Echo canceller interface, QMT21 High Speed Data Module, Tracking mode

Models: NN43001-301

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28ISDN 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" (page 29), 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

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Nortel Networks NN43001-301 Echo canceller interface, QMT21 High Speed Data Module, QPC720 PRI for 1.5/2.0 Mb gateway