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Electrical controls have made a tremendous contribution towards mechanizing and automating many agricultural and food processing operations. In many cases better accuracy and reliability are obtained by the use of electrical controls compared to manual operation. Because of their ability to safely and accurately control equipment, use of electrical controls is continually increasing. Electrical controls are particularly well suited to work with computer-controlled systems. This chapter will consider the concepts of open and closed loop control systems, switches used for control systems, sensing devices for control, and simple direct control systems. The next chapter will deal more specifically with relay-based control systems commonly used for systems in which large motors are involved.