Electronic key

This logic gates circuit may work as electronic key for a door lock or a sicurity alarm. The unlock output (IC2, pin 3) gets high if five keys are pressed in the correct sequence. The gate number five turns on if you press the 5th key and the gate number four is already high. On the previous stages it's the same.
If a wrong key is pressed, one of the gates 10, 11, 12, 13 turn on to activate a reset signal. This happens if you press a key from 2 to 5 and the previous stage (gates 1 - 4) is off.