[Asterisk-Users] BAD/GOOD Echo Cancel

[David Stude]

I've used Voicetronix FXO/FXS ports and noted pretty heavy echo on both
short and long runs to other switches.  We went through some steps to try to
tune the echo out using some settings on the card, and it helped with some
of the higher frequencies, but the problem still remains for many users.  We
decided, based on this and other problems, to pick up a Digium TDM board
with 4 FXS ports and it virtually eliminated all our problems.  The digium
are short run (<20 feet) to our PBX.  

The next step is probably going to be buying a 12 FXS / 8 FXO port TDM24XX
card with hardware echo cancellation.  The FXS will be all short run to our
PBX and the FXO will be relatively long runs to the phone.  So I'm very
curious (and hopeful) that the problems will be much abated.

-----Original Message-----
From: asterisk-users-bounces at lists.digium.com
[mailto:asterisk-users-bounces at lists.digium.com] On Behalf Of James Harper
Sent: Monday, February 06, 2006 5:46 AM
To: Asterisk Users Mailing List - Non-Commercial Discussion
Subject: RE: [Asterisk-Users] BAD/GOOD Echo Cancel

> 
> virtually all software echo cancelers cannot get double echo removed 
> completly.  It can get the first one but not the second one.  There
are
> instances where you get a 2nd echo, so ...  Asterisk is no exception 
> from this afaik nothing software only based is.
> 
> If you really want good echo cancelation a hardware solution is the
way
> to go.
> 

Just an enquiring mind wanting to know, but how is a hardware solution
different to a software solution? The echo cancellers in the Digium hardware
presumably just use the same sort of algorithms as the software versions, so
it is just that they are dedicated and perform better, that they are closer
to the source of the echo, or some other thing that I've overlooked?

Thanks

james
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