In the development of telecommunication networks throughout the world,
digital transmission has now replaced analog transmission as the
predominant choice for new transmission facilities. This trend began in
the early 1960s when the American Telephone and Telegraph Company first
introduced pulse code modulation as a means of increasing capacity in
their cable plant. Since that time, digital transmission applications
have grown dramatically, notably in the United States, Canada, Japan,
and Western Europe. With the rapidity of digital transmission
developments and imple- mentation, however, there has been a surprising
lack of textbooks written on the subject. This book grew out of my work,
research, and teaching in digital transmission systems. My objective is
to provide an overview of the subject. To accomplish this end, theory
has been blended with practice in order to illustrate how one applies
theoretical principles to actual design and imple- mentation. The book
has abundant design examples and references to actual systems. These
examples have been drawn from common carriers, manufac- turers, and my
own experience. Considerable effort has been made to include up-to-date
standards, such as those published by the CCITT and CCIR, and to
interpret their recommendations in the context of present-day digital
transmission systems.