Background

The Corona Institute, which is engaged in vital medical research, wishes to monitor and control access to the rooms and labs in its research division. This facility has a number of rooms connected by doors. Due to "social distancing" the doors are one-way only, providing a link FROM one room TO another. All rooms also have an emergency one-way door to the Outside, which can be used at any time. The doors are controlled by inserting a "Pass" into a pass reader which controls whether the doors will open to let staff through to the room on the other side, or not.