Clicking noise with AVM-Card on ISDN side

Hallo !

I have the following problem :

I run ASTERISKWin32 with a AVM FritzCard under capi_chan and a Grandstream GXP-2000. I use a-law codec, because i live in europe.

If i make (or revieve) a call on ISDN line i have a good sound quality on my softphone (EyeBeam) or my Grandstream, but the caller on the ISDN side hears asynchronously clicking noise that sounds like a radiation detector or static. SIP-to-SIP calls are ok (clear sound, no noise)

I tried a low-cost HFC-S card with cologne chip and i don’t have the same problem. (But it runs not correct, because i can’t recieve calls on ISDN line - so i switched back to AVM)

I don’t even think it is a hardware problem with my AVM-Card, because it works well with SIPPSTAR PBX.

Here is what i have tried in the past :

  • ISDN line checked
  • cable changed
  • various .conf modifications
  • Hardware check (AMD Opteron DualCore 2,6 Ghz, 4GB RAM)
  • AVM-Card changed
  • read many similar topics …

So … PLEASE HELP ! I get insane …