That's a good bit of info, and I think you have done more than most would to
try and fix the issue. Fact is, there is only so much you can do in
software.
Using a hardware echo can will solve the problem totally. If time is money,
paying for the echo can is worth it. We use them standard on all our
systems; whether 2 ports or more, the echo can is simply part of the card.
If the customer doesn't want to pay for it, we don't pursue the sale. Not
that I am a snob or too good for them, but simply because I know the chances
are good that they will not be happy with me if there is echo on their
lines.
I'd argue that echo cans are cheap insurance, and they pay for themselves in
time saved and grief avoided. Not sure if that helps you make your decision,
but do ask yourself what the value of your time is :-)
Jim
--
Jim Van Meggelen
[EMAIL PROTECTED]
HYPERLINK
"http://www.oreillynet.com/pub/au/2177"http://www.oreillynet.com/pub/au/2177
"A child is the ultimate startup, and I have three.
This makes me rich."
Guy Kawasaki
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_____
From: Kevin [mailto:[EMAIL PROTECTED]
Sent: August 24, 2006 11:34 PM
To: [email protected]
Subject: RE: [on-asterisk] Echo on SIP to FXO
I just wanted to give an update since posting in late July.
I still have a little echo/sidetone on my SIP calls that are routed to my
analog line.
I am now using the “Trunk version” of fxotune. This is a must if you have a
Digium TDM400
HYPERLINK
"http://svn.digium.com/view/zaptel/trunk/fxotune.c?rev=1348&view=log"http://
svn.digium.com/view/zaptel/trunk/fxotune.c?rev=1348&view=log copy fxotune.c
to your zaptel folder and recompile. (make, make install) Look at the usage
section near the beginning of the code for the switches. In verbose mode it
will show you the echo and power levels of the coefficients selected. FYI,
you need a silence line to use this version of fxotune. I found that a dial
string of 905 will give me about 16 seconds of silence.
I started out with 14% echo and a power level of 660.
Now I did a bit of reading @ HYPERLINK
"http://www.sandman.com/"www.sandman.com. He has a lot of advice on
troubleshooting analog lines. I ended up ordering an “Impedance matcher”
from them. This did bring my echo down to 10% . The reasons I ordered this
“filter” was two fold. First my Loop Current was a little high (58.6 ma)
Sandman recommends a level of 25 to 35 ma. You need to put a ma meter in
series (tip or ring) with an off hook phone. I also assumed that my
impedance was whacked out, as fxotune was picking a set of coefficients
designed for an impedance not typically found in North America.. This little
device, not only did impedance match but regulated loop current to 25ma.
Well 10% isn’t good enough so I started playing with resistors. I have
removed the Impedance matcher/loop current regulator and after a some trial
and error. I now have 300 ohm resistors on both the tip and ring, and am now
down to power 296 and echo 6.2%
I talked a buddy mine’s friend into testing the line (he works for bell), he
tells me my line is crisp. Oh well I tried!
I wish I could get someone at Bell to check if I have a bridge tap or load
coils on the line. Not likely load coils but very likely a bridge tap. I
don’t know how much difference cutting the back off a bridge tap will make?
Comments?
If anyone has any ideas on how I can get this power/echo down a little more
I am listening!
I have adsl on the line, while I don’t think this is an issue. I also think
my adsl is about half the speed that it should be. I might pressure
Sympatico that my line is bad. Which I think it is. Sympatico may have some
tricks that will cure the sip > analog echo issue in the process. Again any
ideas out there?
Oh, while I am at it, can anyone give me a comparison between Digium tdm400
and the Sangoma A200 with echo cancel. I would like to know how well the
echo cancel works. This would be the pricey fix. In the end it only cost me
20 cents in resistors to bring my echo down from 14 to 6.2%
I am using MG2 cancel and have played with the rx/txgain. I am now able to
tell the difference playing with the gain settings. But, I believe that if I
can improve the line a little more the echo cancel will do a complete job.
Let me know if you would like any more detail.
Kevin Vieyra
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