[asterisk-users] E1 PRI to and from SIP screeching

Eric "ManxPower" Wieling eric at fnords.org
Wed Nov 12 23:06:49 CST 2008

 From IRC:

Echo Canceler Freak Out, this happens when the rxgain is too high and 
the echo canceler freaks out.  Some users describe it as "screeching", 
"feedback", "static", or other useless terms.  If users report "static" 
on a system where there cannot be static (all digital, PRI, SIP, etc), 
you might be experiencing ECFO.

Try lowering your rxgain on the PRI.

Peter Lindquist wrote:
> We have just set up trixbox latest with a Rhino r1t1 card, hooked up to 
> a plain E1 PRI line. We call fine SIP to SIP, but as soon as we make a 
> call from SIP to PSTN all sounds become unintelligible screeching or 
> static kind of noise on both ends, when we call PSTN to SIP the PSTN 
> side seemingly OK at least we hear no screeching sound, but the SIP side 
> is a even worse screeching sound. To be certain all is as plain as 
> possible we disabled all echo canceling, and we use only alaw.
> Any ideas on what this can be and how we start troubleshooting this?

Consulting and design services for LAN, WAN, voice and data.  Based near 
Birmingham, AL.  Now accepting clients worldwide. Contact me for Tellabs 
echo canceling systems.  Also see http://www.fnords.org/skillslist.html

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