This simple circuit uses a Cmos 4081 to create a four-digit code-operated keypad switch - with enhanced security features.
This is a photograph of a universal Keypad-Operated Switch - with a difference. Instead of entering the code one number at a time - the four keypad buttons must be pressed simultaneously. You can also split the code between two separate keypads. If you mount the keypads at some distance from one another - two people will have to be present in order to operate the switch. And each person can have his own unique three-digit security code.
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