I have experienced some trouble with the PPP interface of the FS20.
I used a M1306B with no problem.
with the FS20, when I dial the ATD99**1#, I see the CONNECT 115200 and the first PPP frames.
But then the PPP negociation sometimes succeed (20% of the time) and generally fails.
With M1306B, this is no problem.
The PPP client is from an embedded OS : BECK from germany.