> Well, as I say, I started by wiring up one NAND gate, a pair of switches 
> and an LED. What *should* have happened is that the LED lights up unless 
> you simultaneously press both switches. What *actually* happened was 
> completely different. :-/

How did you wire up the switches to the inputs? You can't just use a 
connect/disconnect switch to the V+ line, because when it is disconnected 
the input will be "floating" and probably float high.  You need to either 
add a pull-down resistor or wire up a switch to connect between 0V and V+ 
alternately.

How did you wire up the LED? LEDs operate depending on current, not voltage, 
so you usually need a resistor in series to fix the current.  Did you also 
check that the IC could source/sink enough current to drive the LED?

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