The modern world is dependent on digital communications. Until relatively recently, radio, television and telephone systems were essentially analogue in nature. The majority of communications, however, still originate in the physical world as sound and images, mainly voice (as in telephone communications), and such signals must be converted to some digital form before they enter the communications links. These communications may be by copper wire, by fiber-optic cable, or by modulated radio waves using either terrestrial or satellite broadcasting. This book will, by necessity, touch on a number of different areas of study, and as such is more than just a text for aspiring Electrical Engineers. The course on which this book is based is a proven method for introducing the student to the subject of communication systems. It integrates and applies the basic concepts found in the student"s other courses and permits the inclusion of material important to the practice of electrical engineering not usually found in the traditional curriculum. This book is intended as an introductory digital communication book for students in computer science and Electrical engineering.