Extra Information

ASPI Digital - The Sound of DSP Application Note: 121

EF1210TEC A

DDENDUM

THE

EF1210

SER

ANUAL

Since the EF1210TEC is largely based on the EF1210, most of the information in the EF1210

User Manual applies to the EF1210TEC. This document describes the TEC features, and the

difference between the operation and configureation of the EF1210TEC and the standard

EF1210.

NTRODUCTION

The EF1210TEC is a unique product that is designed to cancel echoes caused by the transmis-

sion network as well as acoustic echoes in the local room. There are a total of eight echo can-

cellation channels on the EF1210TEC. Seven channels of the EF1210TEC behave as normal

Acoustic Echo Cancellation (AEC) channels. One channel is a Transmission Echo Cancella-

tion (TEC) channel.

The TEC is based on two components. The Transmission Delay Compensator (TDC) deter-

mines the amount of delay in the echo signal. The echo canceller does the actual filtering to

remove the echo, and is based on the same technology that is in all of ASPI Digital’s acoustic

echo cancellers. The TDC essentially moves the echo canceller to the right delay, so that the

TEC (the combination of the TDC and the echo canceller) can cancel looped back echoes over

a much longer time period than the tail length of an echo canceller would normally allow.

It should be noted that the TEC is designed to handle looped back echoes created by the trasn-

mission network, and not acoustic echoes caused by remote sites. The tail length of the echo

canceller in the TEC is not as long as the AEC channels, because it is designed to cancel only

clean looped back echoes. Also, the TEC will not cancel multiple echoes if they are separated

by more than a few milliseconds.

ONNECTING

THE

EF1210TEC

The connections required for the EF1210TEC are fairly application specific. The two most

common applications for the EF1210TEC will be described below.

Figure 1a: EF1210TEC Front Panel

Figure 1b: EF1210TEC Rear Panel

PAGE 1
EF1210TEC ADDENDUM TO THE EF1210 USER MANUAL Since the EF1210TEC is largely based on the EF1210, most of the information in the EF1210 User Manual applies to the EF1210TEC. This document describes the TEC features, and the difference between the operation and configureation of the EF1210TEC and the standard EF1210. INTRODUCTION The EF1210TEC is a unique product that is designed to cancel echoes caused by the transmission network as well as acoustic echoes in the local room.
PAGE 2
Application Note: 121 EF1210TEC Addendum Generating Mix Minus with the EF1210TEC A system using an EF1210TEC can be configured to generate a mix minus. This may be necessary if the system is used with a bridge or MCU that does not have mix minus. That is, if the bridge sends the local site’s audio back to itself. When the EF1210 is used in this type of application, it will remove its own audio from the incoming signal, while allowing audio from other sites to come through.
PAGE 3
Application Note: 121 EF1210TEC Addendum Systems with More Than Seven Microphones If more than seven microphones are needed, one or more EF1210s may be added to the system to provide echo cancellation on each microphone channel. In general, only one EF1210TEC is needed in the room, and standard EF1210s may be used for additional microphones. CONFIGURING THE TEC The AEC channels of the EF1210TEC can be calibrated and configured as described in the EF1210 User Manual.