The code lock describes here can be installed in lockers, almirah or cupboard in homes and offices to protect your important documents or jeweller. In this locker can only be opened when you press the correct code. Advantages of this circuit are: If wrong sequence is pressed it will automatically reset the whole circuit. Only authorised person can open the locker. Circuit is based on single IC that is CD4013. You can also install this code lock in your car’s so that car can only start when correct code sequence is pressed. We have used push to on switch you can also use numeric key pad available in market. This will increase the complexity of the circuit. Read more to find out how the circuit can be made and how it works.