While trying to refresh my knowledge on Boolean Algebra to teach my teen age daughter I found the site very interesting.But I could not relate to the ckt drawing in respect to NOT gate. What the normally closed in red or in black denotes? Could there be some other example on the same NOT gate?

 

can you post your material?

 

Are you asking about what most of us call an http://en.wikipedia.org/wiki/Inverter_%28logic_gate%29

 

Are you asking about what most of us call an http://en.wikipedia.org/wiki/Inverter_%28logic_gate%29

Inverter, NOT gate, same thing

I assume you're talking about a circuit like this one:

The switch is simply used to change the input state from high to low, and vice versa. It's only for demonstration. When the switch is on, the output is off. When the switch is off, the output is on. You don't need a switch for it to operate correctly. Just think of the theory behind it and you won't have a problem