
This intelligent electronic lock circuit is built using transistors
only. To open this electronic lock, one has to press tactile switches S1
through S4 sequentially. For deception you may annotate these switches
with different numbers on the control panel/keypad. For example, if you
want to use ten switches on the keypad marked ‘0’ through ‘9’, use any
four arbitrary numbers out of these for switches S1 through S4, and the
remaining six numbers...