Logic Tutorial: Door with Password
A binary password door isn't too hard to create.
If you use levers, you just need to place an object enabler, connect it to your door model, and of course connect a negate cube to the object enabler.
Then connect an AND cube to the negate cube and connect all levers to either the AND cube or the object enabler to make your password!
If you had 4 levers and you wanted the code to be on, off, off, on, do the following:
connect the first and last lever to the negate cube, and the middle two to the object enabler.