All the sensors of given Figure are NO switches that close when the variable reaches the trip value. Thus, TH represents a NO connection that closes when the temperature exceeds TH, L1 closes when the level exceeds L1, and so forth. The conveyor and stir are motors; the valves and heater are all solenoids.

Prepare a physical ladder diagram for the system of Figure as described in Problem. Be sure to consider any operations that can be executed simultaneously.

Problem
Figure shows a system for batch processing. The system operations can be described as follows:

(1) A weighed quantity of dry material is added to liquid that has filled the tank to level L1.

(2) The mixture is stirred, and heat is applied to maintain the temperature between TL and TH for a period of 10 minutes.

(3) With the stir and heater off, the batch is emptied down to level L2. The whole process then starts again. Prepare a flowchart that describes the sequence of events. Be sure to consider any events that could occur in parallel.