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RE: New Member seeking help to master Echo Cancellation Techniques.

Started by Dharmendra Lingaiah May 13, 2001

Hello Madhu,

I have tried to answer your questions below ...

1. Why 4-wire system is used between Hybrid and PSNT and 2-wire system is
used as subscriber loop.
I believe ...the choice of 2-wire for local loop was purely a COST
CONSIDERATION Factor, it worked out
cheaper to provide a 2-wire connection to every subscriber..rather than
4-wire.

2. How single tone detection is done at Echo Suppressors.
Most implementations use BANDPASS Filters for single tone detection.

3. What is the major advantage of Echo Cancellor over Echo Suppressor.
An Echo Suppressor acts like a attenuator providing a fixed attenuation
level for signals....
An Echo Cancellor on the other hand is adaptive... it estimates the echo and
substracts the echo.

4.What is meant by Non-Linear Echo and howit is taken care over by NLP?
NLP or the NON-LINEAR PROCESSOR acts on the signals provided by the ADAPTIVE
FILTER in the ECHO CANCELLER.
It tries to nullify any additional echo present in the residual signal.
NLP is so called because the "Describing Function" of the Non-Linear
Processor is a NON-LINEAR CURVE.

Regards,

Dharmendra

P.S :- I request the members of the group to correct me wherever I am
wrong..if at all.

-----Original Message-----
From: d_madhu_rao [mailto:]
Sent: Friday, May 10, 2002 12:37 PM
To:
Subject: [echocancel] New Member seeking help to master Echo
Cancellation Techniques.
Hello Friends,

I am a new member to this group and am eager to understand
theoretical and practical aspects of echo cancellation techniques.

Firstly can u plz give me certain site addresses which cover
extensively the above mentioned aspects of Echo Cancellation
Techniques.

I have not fully understood certain issues like,

1. Why 4-wire system is used between Hybrid and PSNT and 2-wire
system is used as subscriber loop.

2. How single tone detection is done at Echo Suppressors.

3. What is the major advantage of Echo Cancellor over Echo Suppressor.

What is meant by Non-Linear Echo and howit is taken care over by NLP? _____________________________________
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Hello Friends,

I am a new member to this group and am eager to understand
theoretical and practical aspects of echo cancellation techniques.

Firstly can u plz give me certain site addresses which cover
extensively the above mentioned aspects of Echo Cancellation
Techniques.

I have not fully understood certain issues like,

1. Why 4-wire system is used between Hybrid and PSNT and 2-wire
system is used as subscriber loop.

2. How single tone detection is done at Echo Suppressors.

3. What is the major advantage of Echo Cancellor over Echo Suppressor.

What is meant by Non-Linear Echo and howit is taken care over by NLP?