An industrial furnace is to be controlled as follows: The contacts of a bimetallic strip inside the furnace close if the temperature falls below the set point and open when the temperature is above the set point. The contacts regulate a control relay which turns on and off the heating elements of the furnace. If the door to the furnace is opened, the heating elements are temporarily turned off until the door is closed.
(a) Specify the input/output variables for this system operation and define symbols for them (e.g., X1, X2, C1, Y1, etc.).
(b) Construct the ladder logic diagram for the system.
(c) Write the low level language statements for the system.