I need some help with this ladder diagram that is for a cooling system. Here is the assignment: The system has two rooms that need to be cooled. There is one evaporator in each room with one fan. The evaporators should have an electric anti-ice system (heat rods) that is to be controlled by a timer and a thermostat. The fans should have a delayed start after the anti-ice process finishes. The compressor has a capacity-regulator that is regulated with a low pressurestat (stops two cylinders when pressure falls). The system is to be controlled by the "pump down" principle with its own LP-pressurestat. The condenser has two fans. One fan should always run when the compressor runs, and the second one should engage via its own HP-pressurestat. The control board should have the following lights: - Running compressor - Compressor stopped by either HP-pressurestat or engine protection. - Anti-ice in any of the two rooms, two lights. There should be these switches: - Start compressor and condenser - Start switch for both rooms Now, the attachment shows a diagram that is supposed to be correct, but I need serious explanation to understand the concept of these diagrams. I have a list of questions I have: - The different squares labeled K1, K2 and so on, these are simply supposed to represent the compressor, the fans, and so on, right? - What is the difference between the type of switches at the red circles A, B and C? - What is the purpose of the magnet valve?