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 <http://svn.digium.com/view/zaptel/trunk/fxotune.c?rev=1348&view=log> &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
