The Security Guard duty monitor below, shown in eight circuits at Digital Circuits – 1 are examples of logic circuits, i have converted them from the DOS Orcad to Orcad 9 and corrected some errors a few years back.
These circuits can be used for looking at the logic blocks or to learn. This product was built and sold to some firms many years back. Now these designs are best done with a PIC or Atmel chip. Here is the user manual
This circuit was done with CMOS CD40xx type of ICs. A RAM was used to store the Day/Time LED Status.
It was to monitor the Alertness of the Security Guard. Periodically the Unit will Buzz and Flash and the Security Guard has to press a Big Button to indicate he is awake, alert, agile and around the Unit.
All Green means fine, few Red LEDs means the Guard was sleeping or gone away from some times. All Red means Security Guard is missing. :-)