asterisk users - Oct 2004 - More Reverb like Echo when calling for analog to ISDN - CAPI Fritz - what can I do ?

Hi,

when I call from analog phone line to our ISDN Fritz! Usb card with CAPI and
Asterisk I get echo that is more like recursive reverb than distinct echo.

Do I have any settings, configuration (Fritz card, Asterisk) to try to avoid
this problem ?

Thanks in advance,

regards,

Robert.