two seprate circuits, one switch?

just wanted to say thanks again guys. I think oldspark's design will be perfect for what I have in mind but now I have to find time to impliment it.I'll report back with my results or further questions depending on what I get into here.

OK this works exactly as expected. thanks again OS! now how would this diagram change if S2 controlled LED fog lights? I assume I can eliminate the relay shown on the top right but everything else in this diagram remains the same for this purpose, no? thanks

two12 wrote: this works exactly as expected...

OF COURSE! What did you expect? (READ: Phew - I fluked it yet again! No misunderstandings, no stupid errors.) And you are correct about NOT having relays. The relays are mainly there to take the load of the switches and diodes. They also allow full voltage to the load (ie, no diode voltage drops) or allow total independence of the load (eg, a 24V or 48V loads etc; maybe AC loads with appropriate relays and regulatory conformance...)     If the LED foglights are within switch and supply tolerances, and diode rating (1A, 3A, whatever), then no problem. They will be a bit dimmer though (eg ~0.7V in ~12V "dimmer"). Remember the diode's heat - ie, ~0.7 x I Watts where I = current (Amps).