Overview

Introduction

The DSP Series 2 card Echo Canceller removes echoes caused by signal leakage at hybrid telephone line interfaces. You may want to implement an Echo Canceller for tandem calls on trunks with echo, or to clean an incoming signal before connecting to a media resource, such as a VRU or AMD.

Call Processing Event

The following event is sent in a Call Processing Event 0x002E message when a G.164 tone disabling event occurs on the near or far end.

Event: 0x49 - Echo Canceller Event

Alarm

A General Alarm (0x41) is sent in the Alarm 0x00B9 message when the Host requests to attach a receiver to a channel that already has an Echo Canceller attached but there is no resource available on the same slot as the Echo Canceller resource. This means that the receiver will not receive the output of the Echo Canceller, but will receive the original signal with any echo that may be present.

Resource Modify NACK

The following response status values may be returned for the Resource Modify 0x0125 message:

0x1708 - No Active Echo Canceller

Returned when the switch receives a Resource Modify message with the Resource Type of Echo Canceller and there is no Echo Canceller attached to the Channel.

0x1709 - Invalid Echo Canceller State

Returned when the switch receives a Resource Modify message with the Resource Type of Echo Canceller and there is no Echo Canceller attached to the Channel.