This circuit can be placed at the entrance to a room or building, and will count the number of people entering and exiting using the two photoresistors at the bottom of the board. This will then update the 7-segment displays, so you can judge if the room or building is already at capacity. In addition, two digital outputs (labeled "Y" and "N") will trigger depending on if the current measured population is above or below capacity, to allow for automation of other systems, like signs, doors, or alarms. The sensitivity of each photoresistor can be modified using the potentiometers on the board, and toggling the "Test" switch will make it that your testing of the photoresistor sensitivity will not count towards the actual capacity. If multiple modes of operation are needed, a "Mode" switch is present, that can shift how the code functions (i.e. different capacity levels, different brightness of the display, etc.) In addition, anybody the photoresistors missed can be added or subtracted using the manual "Up" and "Down" buttons on the bottom of the board.