why both usually the brights are enough to see everything. but i really wouldnt mess with it. try to find a repair shop with someone who does electrical maybe they can help
its called google...and im pretty sure it vaires on the type of vehical...try this tho...http://www.rowand.net/Shop/Tech/images/HeadlightRelayWiringDiagram.jpg
caraudio install are you talking about having ur brights and bottom fog lights on also like in a truck?(wanted this also //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif )