Voice quality PSTN calls

Hello all.

I’m using TDM411B, and some SIP softphones. When I’m doing internal calls (not using PSTN) the quality is acceptable. But when I call to the pstn the voice quality is very bad, there are cuts, conversation goes and return, etc. Do you know how to correct this…?

I´m using asterisk 1.2.7, Digium TDM411B, X-lite softphone
and PC PIII 533 Mhz. 256 Mb. RAM

I have close to the same setup as you do except that I’m using the FXS port of the TDM411B for my phone and don’t use any soft phones. Have you tried to connect a regular phone to the FXS port of the TDM11B? All my calls that go out the PSTN line are crystal clear.

was it ever working?
is your pstn line ok with a regular phone without asterisk box?
consider reseating the tdm400 card in its slot or a different slot.
consider that you may have a bad card/module that should be under warranty.