This exciting revision of "Communication Systems", a classic text in the communications field, presents an introduction to electrical communication systems, including analysis methods, design principles, and hardware considerations. The fourth edition has been completely updated to reflect current technology in this ever-evolving field. This edition also features two new co-authors: Janet Rutledge of the University of Maryland at Baltimore and Paul Crilly of the University of Tennessee at Knoxville, in addition to author Bruce Carlson of RPI. The book is intended for an introductory communications course, and is written at a level appropriate for advanced undergraduate and first-year graduate students. The fourth edition covers both analog and digital communications. It features worked examples and exercises for students to solve within chapters, helping them to master new concepts as they are introduced.