The book explains data communications systems and their various hardware and software components. Organized like the highly successful 5th edition, the book takes a textbook approach to the complex issues surrounding the understanding of data communications concepts. This format allows the reader to tailor the book to their needs. If their objective is to obtain general information about a subject, they can bypass the more detailed portions of the text and take the quiz to test their knowledge. If they really want to delve deeper into a topic they can focus on the specifics of the chapter and refer to other books listed in the bibliography for additional information. The author provides a basis for understanding data communications systems in general, and provides expertise on setting up specific types of communications systems.