Echo and power outage

Hi everybody,

I often need to reconfigure my system after a power outage because the echo was worst. I would like to know why and what should I do to avoid this from happening again and again.

Thanx for having read.

Are you trying to say that your lines change quality even without the server rebootng?

If that is your questions, my guess is it’s not the electrical surge at all but the moisture accompanying the storm. Wet connections have different impedance characteristics so will sound different.

What do you have to do to “reconfigure my system” ?

Just some few things like changing the values of echotraining and echocancel in chan_dahdi.conf, restarting Asterisk and Dahdi and then see if it’s better.

starting dahdi causes dahdi_cfg to be run that parses /etc/dahdi/system.conf, so check the contents of thatfile. It also calls fxotune that reads /etc/fxotune.conf, unless you have run fxotune -i it wont be very successful.

If you have the dahdi module installed, I suggest you do all your changes there as many of the /etc/asterisk/dahdi files will get regenerated on a restart.

Thanx for your advice, dicko. But I also need to know why this occurs after power outage since my line is protected by an arrester?

Does it happen after a reboot as well?

It’s possible that after a power outage, the system stops and start again at the return of the current. I’ve configured the Bios for the machine to react like this.

My real question is why would you think a surge arrestor would help?

If you had a battery backup with sufficient time to keep the system running that would help.

Why don’t you just configure the fxotune to be run at startup?

The system has an UPS but when the power outage takes too long it will also stop.

“Why don’t you just configure the fxotune to be run at startup?”

Because I also need to understand the mecanism explaining that and that won’t keep me from opmizing my configuration.

I don’t understand what you mean. The FXOTUNE parameters are written to a file. They have to be applied to the card any time the card is reset.

The tuning procedure is a matter of setting prescription levels to compensate for impedance mismatches in the physical circuit.

It occurs because you have not made any of your changes permanent over a reboot. It has nothing to do with arresters or power outages.

man fxotune

and google fxotune to see why it is necessary.

I will try to be clearer. When this problem occur, I knew that I had to do some things to stop this from happening again but first of all I wanted to know how it was possible that power outages degrade a previously good echo quality especially as I don’t have great knowledge in electricity.

First, find out if it’s a telephone line issue or a power line issue.
For ex.: on a nice day, no rain, little moisture, PBX working fine with little/no echo etc., pull the plug on your PBX server (OK, you might want to do a clean shutdown instead of pulling the plug…).
Restart the server as soon as possible.
Do you have the echo problem?

If yes, then it’s not a telephone line issue (there was no rain before, there is no rain now). If yes, it is probably something that is not set up correctly when your PBX boots up (or something that is not saved correctly when your PBX shuts down).

You mentioned an UPS: does your PBX “talk” to the UPS, so when the UPS is low in charge the PBX shuts down cleanly? Or when the UPS dies, so does the PBX?

An electrical power issue is very unlikely: you would need huge interference on the electrical power line to generate problems on the (analog?) phone line.

Thank you so much for your precious sharing. I’ll comme back after some tests.

Just to say that I think that the line quality falls after rebooting and not before it. When I change echocancel setting, after rebooting (not all the server, just asterisk and dahdi) the line quality is improved and that last many months. I’ve installed this system many month ago and during all this time, no echo problem where noticed. But it’s after a general electrical problem (that damaged the main UPS not the one in the rack just under the IPBX) caused by a technician that every few weeks (2 or 3 weeks) echo problems are noticed and I have to reconfigure things. Before this general electrical problem, things were cool. That’s the source of my worries.

Precision. When I say “the line quality falls after rebooting”, I mean a reboot after the server being stopped because of a lack of energy.

Finally, the problem is solved. In fact, there was an hardware echo cancelation but it seems like it has receive a shock during the electric problem that hurts the system, damaging one of the 4 X100P previously functiunning. So I replace the failed one by a new. But I will remember all your good advices.