Echo problem

I have a TDM400 card and using asterisk 1.8. The problem is when I make an outgoing call I can hear myself in the handset of the phone better than the person on the other side. The same thing happens on speaker phone. This only happens with outside calls.

I too am experiencing this on a TDM-800P with on board echo cancellation after upgrading the FreePBX distro from to 1.810.210.57-1.

Other forum posts indicate a possible issue with either DAHDI 2.6, the updated linux kernel or a conflict between the two.

I would reach out to Digium on that since its their card and their echo cancellation.

I spoke with Digium tech support today: their initial thought was that the latest firmware for the VPM was not included in the DAHDI 2.6 package of the FreePBX Distro. As it was not loading, as seen in the dmesg|grep VPMADT032 command.

Tech Support downloaded and installed DAHDI 2.6 from source. Initially restarted DAHDI without restarting Asterisk. Echo issue was still apparent upon testing even though firmware appeared to load successfully. Restarted Asterisk and DAHDI together and system is back in a fully functional state without the echo issue.

Unsure if the manual download of the firmware or recompiled installed of DAHDI 2.6 actually resolved the issue.

I tried to downgrade to 2.5 and I still have the same problem.

Tigger, following are two different options for resolution:

  1. Please read the following entry It contains some useful information like:

The first thing to check if you experience echo cancellation with…TDM400 cards is that the PSTN loadzone is set correctly… if running in FCC mode, and you are connected to a UK PSTN line…You will need to change to using UK mode.

  1. If the above does not help, try using software echo cancellation like PBXMate

Hello I solved this problem like this:

from the command line on “puTTY”

service asterisk stop
service dahdi stop
fxotune -i 4

this will create the file /etc/fxotune.conf

note fxotune exist to compensate for junk lines. You may wish to get your wiring looked at.

Respectfully James, I would have to disagree, a vast majority of copper pairs will benefit by that tuning. The math behind it is to send an inpulse on the circuit and use FFT to analyse the echo, all phone lines have complex impedance composed of resistance capacitance and inductance, all of these affect the transmission and even in the same MPOE there are always differences between the pairs, the RX and TX paths need as much separation as possible through the 2-4 wire hybrid and fxotune -i does a very good job. Any further echo cancellation can improve voice (but not faxes) but they all work better if the hybdid is optimized.


(and perhaps surprisingly, that doesn’t mean that rx/txgain’s do not also need to be also tuned with a milliwatt test, these are the absolute first two things that I do on every fxo line. If you do that your clients will be much happier :wink: )

This runs on the “last mile” ideal. Over the last 20 years the last mile has reduced to about the last 1000 feet. Some areas with poor infrastructure where they expand beyond capacity or have old wiring this becomes very important. This is also very important in some rural areas. In a lot of urban areas these issues are on the customer side of the DMARK. I can bring fiber to the curb and run copper the last 100 feet but if you have 50 year old copper in your walls. none of the other stuff matters. With my previous employer we put echo cancellation on all analog cards. In reality it is only needed about 10% of the time. The cost to make the card with EC was negligible so everyone got it. In most cases stuff works out of the box without a need for EC or to balance the hybrid. If you are in the 10% that needs this stuff you will be happy you have it. The other 90% don’t really care because they don’t have to.

And how will they know they are in that lucky 10th percentile without taking those extra steps? just run the tests and look at the fft coeddicients it spits out into fxotune.conf, if they are all 0, and I very much doubt that even on a Fiber to the curb circuit, (I speak with a little experience here.) then remove fxotune -s from your /etc/rc.local :slight_smile:

I think that all this is just due diligence for any installer even today.