AND gate

Before we go any further, what do you suppose an AND gate does?

Think about it a second ... since you know what an OR circuit does, what would it be logical (pardon the pun again!) for an AND circuit to do?

As you build this Project, make sure the Select Switch is set to B. Now put power ON and press the Key. What happens?

Now release the Key and set the Select Switch to A. What happens now?

Finally leave the Select Switch at A and press the Key. Anything different happen?

You saw that nothing happened until you had the Select Switch at A and the Key pressed. When you had both inputs at 1, LED 1 came on.

An AND gate is a circuit whose output doesn't come on until all the inputs are also on. You can see that the AND gate "adds" inputs.

If the number equals the number of inputs it has, an output results. If not, no output. (Say, do you suppose an AND gate could be used in computers or calculators? No fair peeking at the answer.)