Am trying to set this up with a friend over cable modems

I have the same problem with PtW. In GameSpy the voice chat works, but then when I launch PtW I have no idea how to initiate a voice chat session. The manual only states that it is possible, but it does not say how to do it.
What does the Manual of Conquest exactly say about voice chat?

With friendly greetings,
Erik Hendriks.