What is "digital telephony"? To the authors, the term digital telephony denotes the technology used to provide a completely digital telecommunication system from end-to-end. This implies the use of digital technology from one end instru ment through transmission facilities and switching centers to another end instru ment. Digital telephony has become possible only because of the recent and on going surge of semiconductor developments, allowing microminiaturization and high reliability along with reduced costs. This book deals with both the future and the present. Thus, the first chapter is...