[Asterisk-Users] Static and echo on PRI

[Andrew Kohlsmith]

On April 27, 2005 12:03 am, Mark Johnson wrote:
> day now.  What I find strange is this...  If I speak at a normal tone,
> it sounds OK.  I still get static noise when the other person speaks.
> If I talk louder, I start to get what sounds like a partial echo.  If I
> yell, I get a definite echo.

It almost sounds like the card has an odd gain problem on receive.  The echo 
you hear of  yourself at high volumes I'd call "normal" with the software 
echo cans.

Oh yes -- Digium also has TE405Ps and TE410Ps *with* onboard hardware echo 
cans now.  I have one coming in.

I forgot about the loopback test; use zttool and throw the span into loopback, 
do you see errors?

> When monkeying with the echo cancel, I never really noticed a
> difference.  I would even reboot the machine between changes to see if
> it made a difference.

echocan's a finicky little thing.  echotraining does work but I never use it 
because the delay at the start of the call is unacceptable to me (most of us 
have headsets so the delay between picking up the phone and getting it to 
your ear is almost zero).  The agressive echo canceller basically turns the 
phone into a half-duplex system.  It's a brute force way of eliminating 
echo.  :-)

> I am running this on Fedora Core 1.  I will try any OS you recommend,
> but I have always had great luck with RH type distro's.  I keep 400 and
> 500 day uptimes on those machines and they run many, many services.
> Uptimes would be higher but it seems whenever I find a good place to
> work, they close up or I move.  Admittedly, I don't use RPM's for the
> core services, I typically compile those myself.  I also shut down every
> module and service I don't need.  I did alot of reading and it seemed
> like Digium cards were the real deal and I also found many users that
> had luck with the same setup.  Should I try a different approach/OS/system?

Stability isn't the issue here; it's interrupt latency and kernel delays.  
Personally I run Slackware for everything but I am certain there are many 
people here running FC1 for their systems without any issue, so at this point 
I am not suggesting dropping it.  I'm not sure whether those who are running 
FC1 are running it with Fedora's kernel or with a stock kernel, but I *have* 
seen people with distro-specific kernels have problems that disappear when 
they use a stock kernel.

Which motherboard are you currently using?  Which have you switched to for the 
test?

The great thing about Linux is that in most cases you can (and I have on 
*many* occasions) pull the hard drive out of one system and install it on a 
totally different one and it just works.  Perhaps some minor tweaking of 
ethernet drivers but for the most part there are no hassles.  

-A.