TDM410P noise on FXS ports

I am experiencing a noise problem on the FXS ports of the TDM410P card in my system.
The FXS ports are normally connected to a GPT PKS-2 PBX, but the noise is present
even with just dumb analogue handsets connected directly to the FXS ports. The noise
is only audible on the FXS lines; the other party in calls does not hear any noise.
It does not make any difference whether the other party is connected via SIP, or the
FXO port on the TDM410P card.

I have so far tried disabling echo cancellation and providing external 12V supply to
the TDM410P card from a battery. Neither resulted in any change to the noise.

For system details, see … details….

I have recorded a few sound samples, both with asterisk running and calling into a conference,
and without asterisk running:

dahdi_monitor 2 -m -T tx_conf.raw -R rx_conf.raw -l 200000

; call conference extension

sox -r 8000 -s -b 16 tx_conf.raw tx_conf.wav ; sox -r 8000 -s -b 16 rx_conf.raw rx_conf.wav

amportal stop

dahdi_monitor 2 -m -T tx_2.raw -R rx_2.raw -l 100000

sox -r 8000 -s -b 16 tx_2.raw tx_2.wav ; sox -r 8000 -s -b 16 rx_2.raw rx_2.wav

dahdi_monitor 3 -m -T tx_3.raw -R rx_3.raw -l 100000

sox -r 8000 -s -b 16 tx_3.raw tx_3.wav ; sox -r 8000 -s -b 16 rx_3.raw rx_3.wav

dahdi_monitor 4 -m -T tx_4.raw -R rx_4.raw -l 100000

sox -r 8000 -s -b 16 tx_4.raw tx_4.wav ; sox -r 8000 -s -b 16 rx_4.raw rx_4.wav

amportal start

The wav sound files are available at
With dahdi stopped (/etc/init.d/dahdi stop) the noise disappears, but when dahdi is
restarted the noise reappears again.

The noise is much more pronounced through the handsets than in the recordings and
tends to interfere with the voice in the calls, resulting in complaints from the users of
the system.

Any suggestions for the cause of the noise and a way to eliminate it?



Hello John and All,

Its been more than a year now I know, but I would like to find out how you fixed this problem, I have the exact same issue, heard the audio dumps you posted, and are exactly the same noises over here. I am using a cheap TDM410p card I bought from ebay to a guy in China. I don’t want to blame the quality of the card just yet, hopefully its a configuration thing. The other possibility is that I am using a very small system with a small power supply:

Intel® Atom™ CPU D510 @ 1.66GHz
Generic power supply 250w
1 250GB Seagate HD
Ubuntu 10.10 desktop
DAHDI Version:

Any ideas please?

Buying clones doesn’t support Asterisk, it puts money in the pockets of people that don’t do anything to bring you Asterisk.


Did I make a mistake buying it? Should I throw it away?

yes, you should buy digium or sangoma card for your system. the “cheaper asterisk cards” are really bad.

yes, you should buy digium or sangoma card for your system. the “cheaper asterisk cards” are really bad.[/quote]

But with all respect:

Digium Card with 2 x FXO, 2 x FXS = $637.78 USD
Chinese Card with 2 x FXO, 2 x FXS = $84.94 USD

Maybe Digium could work on making these a little more affordable and people would buy more from them…

For what its worth, I get noise on my cheap FXS ports too - it works, but not noisy enough to justify spending 7x the cost on an official card…

Oh, and as a data point for people, I changed my module load options to:
options wctdm24xxp latency=6

Hey Presto - the noise went away.

If I used the settings for Australia, I got noise:
options wctdm24xxp opermode=AUSTRALIA

Hope this helps someone.

They’re very affordable. You’re welcome.

To what market? Certainly not the individuals. Corporates maybe - but keep in mind that you can buy an entire PC for less than the cost of this card.

EDIT: For the google archives, I’ve added a quick article on what fixed the noise for me… YMMV… … gue-cards/

You get what you pay for. Digium develops their own stuff. You pay for development and quality parts. They use the money to pay the Joe who’s developing it, provide support for YOUR PROBLEMS, and research new tech. Sorry you are having problems. Yes, I think it’s a lot of money too, but remember you are investing. And yes, I did buy a Digium card.

I wish that was the case. I have paid for g729 licenses that were refused a rekey due to hardware changes. I’ve had Fax for Asterisk licenses that were buggy and didn’t work correctly - ever. Now this is in the past and I now use the free g729 codecs and the free fax modules without an issue - but I certainly wouldn’t agree that I got what I paid for.

In my experience, my problems are mine to fix - paid product or not. Yes, the Digium support guys have been very nice and polite, but just about useless in solving anything but the basic issue. I have better quality responses from the community for just about any issue vs the paid support.

I’m not sure the average home tinkerer wants to invest. They want to play and tinker. The people playing and tinkering are the ones that have made Asterisk what it is today. From what I see on the bug trackers, Digium fix about as much as Linus does on the kernel - very little. Their main role is overseeing things.

I would much rather get my hands on a card with zero support (apart from warranty) for a decent price than pay through the backside for the same - which is currently the case…

I don’t believe there are any royalty free G.729 codecs, although there are some that are misrepresented as such. At least one of those is misrepresented as being under the GPL, which it can’t be, as it is derived from code with a no-commercial use restriction.

Are you saying that you were refused a new key by a real person for the hardware change, or just that the licence enforcement software exceeded the limit; normally there is a manual fallback process where you can justify the unusual number of hardware changes, although I don’t know what Digium do in this respect.

This may be the case, but it works. I figure my licenses can be used anyway - even if it isn’t true.

Correct. The keys are tied to hardware MAC addresses of your network interfaces. The code wasn’t smart enough to understand if udev renamed an ethernet card from eth0 to eth1 etc and would invalidate the licenses at every boot. After about 4 times re-licensing before I realised the issue, I was told “Sorry, we only usually relicense the codecs a couple of times - and you’ve already had those - we don’t believe you’re using them on the one system”.

While we’re getting quite off topic now, the point is that yes, I was refused by Digium support for something I paid for - so I wouldn’t recommend to anyone to go down that path.

Hey gang, I just noticed one of my FXS card seem to have heated part (orange parts was darker). I just removed this FXS (now running with 2 fxo and 1 fxs and it’s working. dont know if it’s a power issues ober the pci circuit of the chiness infineon board or just the FXS was bad and making noise over the other fxs…

can you told me if it’s working for you ?

Board TDM400/(TDM401P) infineon