This book presents material in a clear and easy-to-understand manner. All important concepts, rules and formulas are highlighted after the explanation and are also summarised at the end of each chapter, making it easy to locate important facts and to study more effectively. The laboratory experiments at the end of each chapter are convenient for doing hands-on practice. These will motivate readers to master the circuit theory, especially college and university students or self-learners in this field. The English version of this book continues in the spirit of its successful Chinese version, which was published by Higher Education Press (the largest and most prominent publisher of educational books in China) in 2005 and reprinted in 2009.