asterisk users - Apr 2005 - X-Lite to Zap, no Voice on other phone!

Hello,

The problem is - and i was wandering if anyone knows the solution - is 
that When I dial from my windows machine,
to an external phone line through Zap, then the receiving party does not 
hear my voice - but when the receiving party
calls me back, then we have voice on both sides. What makes the more 
currious is that internal numbers work fine, both
sides have voice.

-- 
Kind Regards
Etienne

> The problem is - and i was wandering if anyone knows the solution - is
> that When I dial from my windows machine,
> to an external phone line through Zap, then the receiving party does not
> hear my voice - but when the receiving party
Do you have Transmit Silence=YES on the X-Lite? It's under audio settings. 

What is the NAT situation?