In-Game Chat

[Glendale]

Hi
I'm a newbie to SH4 and I hope someone can help with my question.
I noticed in multiplayer, that there is an option for in-game chat which
switches between 'NORMAL' and 'RADIO'.

This means there is in-game chat between players on LAN?
And how do you actually use it - I pored through the manual and can find
no reference as to how to make use of it, either Radio or Normal.

Can anyone help to clarify please?

Thanks