[asterisk-users] TDM400 native bridge echo

[Tzafrir Cohen]

On Mon, Nov 20, 2006 at 06:09:19PM -0700, Shaun Kruger wrote:
> I have a TDM400 with an FXS and FXO interface.  I have adjusted the TX
> and RX gain for both the FXS and FXO channels so that everything is
> balanced.

gain tuning should be the last resort. 

Before that:

1. Make sure you have the proper value for opermode (if this is the US,
the defalt, FCC, is probably OK).

2. Use fxotune to further adjust the FXO modules.

3. Make sure you actually use an echo canceller.


> 
> I hear myself very loudly with no lag.  I also get alot of background
> noise when the bridge is formed between the FXS and FXO channels.  I
> have read the following articles:
> http://www.voip-info.org/wiki/view/Asterisk+echo+cancellation
> http://www.voip-info.org/wiki/view/Causes+of+Echo
> 
> I have read these multiple times.  My system is now useable, but it's
> definitely worse than when I plug the phone directly into the wall.
> 
> My loadzone is 'us'.
> I have the following in my zapata.conf
> usecallerid=yes
> transfer=yes

siganlling = ???

> 
> channel => 1
> context=outbound
> mailbox=00
> channel => 2

You don't cancel echo on the FXS(?) modules? Why not? Echo should be
cancelled as close as possible to the source: this will make it the most
effective. What happens when you call from an FXS port to a VoIP phone?

> 
> echocancel=yes
> echocancelwhenbridged=yes
> context=inbound
> signalling=fxs_ks
> faxdetect=incoming
> busydetect=yes

You use KewlStart and still have to reort to busydetect?

> busycount=5
> rxgain=5.2
> txgain=-0.5
> channel => 3
> 
> Is there anything I'm missing?  I assume there is because it's not
> working as well as I had hoped.  Any suggestions of what to try next,
> what to look for, or what additional documentation I should be reading
> would be much appreciated.
> 
> Shaun

[1] Actually: once you run 'reload', you will. Confused? 
http://bugs.digium.com/view.php?id=7877

-- 
               Tzafrir Cohen       
icq#16849755                    jabber:tzafrir at jabber.org
+972-50-7952406           mailto:tzafrir.cohen at xorcom.com       
http://www.xorcom.com  iax:guest at local.xorcom.com/tzafrir