Build exactly one

The right bulb combines the gates you already know.

OR asks, "Is at least one input on?"

AND asks, "Are both inputs on?"

NOT flips AND's answer.

A final AND keeps the cases where OR said yes and the both-on check said no.

Together, they say: one input or the other, but not both.

Flip A and B. The two bulbs show the answer as a two-digit pattern.