This is a book about classical feedback control, complete with a review of the linear system theory that can be a stumbling block for many interested in feedback. The author had four groups of people in mind when writng this book.The first group comprises struggling undergraduates who despair of moving forward because too many things simply do not make any conceptual sense. The second group are the star test takers who find that they must put all that they learned out of their heads and rely on an entirely different set of skills to build physical systems, and who wonder why this is. The third group are the young graduate students preparing for their doctoral qualifying exams and find that a deeper level of insight is called for than was needed in their undergraduate years. And the final group are the successful professional practitioners who have made themselves very effective despite a secret unease with the physical foundations of their field.If you fall into one or more of these categories, or if you are simply curious, this book is for you.