The present book is meant for the first-year engineering curricula of various universities in India. It describes the basic theories of electron dynamics, semiconductor physics, semiconductor diodes, bipolar junction transistors, field-effect (junction, MOS and CMOS) transistors, voltage and power amplifiers, oscillators, power electronic devices (SCR and UJT), and operational amplifiers. It further describes radio, mobile, fiber-optic, satellite and microwave communication systems. It also deals with the basic theories of radar, electronic instrumentation, Boolean algebra and logic functions. The book has more than 250 diagrams to illustrate the theories described and numerous worked examples.