S-video output

​ I want to use the S-video output jack to display documents which are open on my desktop to a TV or a video projector. I can get the wallpaper to project by enabling the secondary monitor through the S-video jack, but when I open a document, the video out remains as the wallpaper. If I function F8, it disables the secondary monitor and the external display goes black. Of course I have tried function F8 toggles several times, but nothing. I have also searched the Knowledge Base without any luck. Where can I get instructions or limitations for using the S-video out? ​