This is a great tool and you can easily rename the dump file to fxotune_dump.csv to open and graph it in excel.
For those who cannot get the patch to work here is a download link of the already patched file from the csv. http://svn.digium.com/view/zaptel/trunk/fxotune.c?rev=1172. Just move it into your /usr/src/zaptel directory and recompile using make.
I noticed that with ADSL and a filter on the line my echo percentage was close to 20%. If I remove the ADSL from the modem (but still leave the filter in) the echo drops to 13%. It iss only when i remove both the ADSL modem and filter and plug it directly from the wall to the TDM card that the echo drops to under 5%.
Has anyone had a similar problem? If so, how did you sold it.
I realised that i was not applying the settings using fxotune -s. Once i did that, even with the ADSL modem and filter the echo fell dramatically to 3% which the echo canceller should be able to handle (so we are told above).