Part of Delmar Learning's new National Center for Telecommunications Technologies series, this book begins with the history of the public switched telephone network (PSTN). Descriptions of public and private telecommunications networks, plus a basic electronics refresher, are provided. Subsequent chapters offer a complete overview of existing network infrastructure, with discussion of analog and digital signals concepts, frequency spectra, plus modulating and multiplexing techniques. System hardware is also introduced, including transmission and reception technology, switching systems and more.