The present book, viz., Concept of Facts covers the undergraduate and postgraduate syllabus of the Anna University affiliated colleges. It caters to the requirements of the students of Electrical and Electronics Engineering of those colleges. It also serves as both textbook and reference work for a course of Facts Controllers. The topics in this book have been discussed in such a way as if a teacher is explaining the subject in a lucid and comprehensible way. The subject matter is supplemented with a plenty of neat labelled diagrams. Students of other universities, research scholars and practising engineers will also be benefited from this book.