Hi Kevin, I believe that the load coils are removed when you have DSL.
Kevin wrote:
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
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 @ www.sandman.com
<http://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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Henry L.Coleman [ VoIP-PBX ] Tel.1 866 415-5355 Ext.301
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