(Solved): 4. (10 marks) To prevent access of unauthorised persons, a security system is designed such that ac ...

4. (10 marks) To prevent access of unauthorised persons, a security system is designed such that access is only provided when two push-buttons are presged within one minute of each other. (a) Using a 555 design a circuit that creates a minute delay ( 4 marks) (b) Design a circuit that produces an output (HIGH) if two push-buttons are pressed within one-minute of each other (3 marks) (c) To add another layer of security, an override push-button is added. If this button is pressed the output goes immediately LOW. Modify the circuit built previously to include this. (3 marks)