Either one

If any single switch is on, the lamp lights. The friendliest two-input rule. Build an OR gate — the "generous" cousin of AND.

What you'll learn

• The OR rule: output is on when any input is on.
• How OR mirrors AND — they're opposites in the "how picky am I?" sense.
• Spotting OR in the wild: alarms, safety overrides, "any of these is enough" checks.

The idea

AND is strict: every input must be on. OR is permissive: any input is enough. Those two rules — strict and permissive — pair up to cover most of boolean logic.

A useful way to think about it: AND says "yes" to the intersection of inputs that are on, OR says "yes" to the union. If AND is the cautious bouncer, OR is the welcoming host.

The challenge

Wire two Levers (labeled Input A and Input B) into an OR gate, and the OR's output into a Lamp labeled Output. Flip through all four combinations. Notice that three of the four rows light the lamp — OR is the hardest rule to make output zero.

Where you'll see it

• Any "this OR that triggers the alarm" situation.
• Combining multiple clock ticks, keypress detectors, or sensor trips into a single "something happened" signal.
• Inside every adder — the Carry line of a full adder is an OR.