[Asterisk-biz] PRI and echo cancelation ...

[Jeff Grammer]

I have an installation using a PRI line where on "some" calls, (even to
calls on other PRI's, not just analog lines), have echo problems.

Is there anything other than CPU clock speed or other methodology to
determine where the echo is coming from and how to correct it?
 
Thank you very much for any help,

Jeff Grammer 
 


-----Original Message-----
From: asterisk-biz-bounces at lists.digium.com
[mailto:asterisk-biz-bounces at lists.digium.com] On Behalf Of Rob Lith
Sent: Thursday, August 18, 2005 3:29 AM
To: Commercial and Business-Oriented Asterisk Discussion
Subject: Re: [Asterisk-biz] PRI and echo cancelation ...

On 8/17/05, Michael Blood <Michael at matraex.com> wrote:

> Agreed,  this should be on the Users List.
> My experience has been that PRIs have much less trouble.
> The echo typcially comes from the analog to digital conversion.

No, it happens because of the impedence difference between 2 and 4 wire
analogue lines which causes a reflection point - this is not possible on
Digital lines.

The only instance you'll get classis 'echo' is when calling from you ISDN to
an analogue line on the far end.

> I personally believe the reason for this is that the Analog to Digital 
> conversion that happens at the telco is done with much higher quality 
> equipment with much higher quality echo cancellation than if it is 
> done on your asterisk box.
> 
> Here is an interesting read
> http://www.voip-info.org/wiki-Asterisk+echo+cancellation
> 
> Google Search:
> site:voip-info.com echo cancellation
> 
> Michael

Regards
Rob
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