D800 Conexant D480 Modem, no microphone input?

I tried to make telephonecall with this D800. The sound from 'the other side' is heard. That works, but they can't here me. I'm using standard telephonechoice from Windows 2000. I've already checked the options, I can choise input from my soundcard if i communicate true internet, but if I'm choose for the modem and telephoneline, the option input sound and outpur sound are grey.

Can someone help me, so I can use this modem and laptop to do some telephone calls (without using the standard telephone)

Waiting for your reply,

Best Regards

Peter Boermans,

The Netherlands