> Funny, I thought I *already* had a basic knowledge of how circuits work...

The circuit diagram you posted here makes it look like you don't.

> I guess what's throwing me is this new "logic low = negative" thing. I'm 
> used to thinking of logic low as "nothing connected here".

OOC why are you used to thinking that?

> If you were making a bunch of logic out of switches with either connect or 
> don't connect a wire to the positive rail, everything would be quite a bit 
> simpler. (E.g., connecting the output of two gates together couldn't 
> possibly create a short-circuit condition, since each output is connected 
> to the same battery terminal or to nothing at all.)

This doesn't work, because as soon as you connect a "not connected" output 
to something, it becomes "connected" and will have a specific voltage.  The 
severely limits how many things you can connect to a single output.

> Uh, no, even I'm not crazy enough to want to do that. :-P

It was just an example, you might one day want to control a motor, a 
brighter lamp or a heater or something.

> 3. Relays presumably use about 100x the current that an IC can supply.

Hehe no, I've got a tiny surface mount IC here that is driving 6W of LEDs 
directly.

> 4. PROFIT!

Huh, what are you planning to sell? No more free advice :-)

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