Principles of Synchronous Digital Hierarchy

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Advent of Digital Technology

In the previous chapter, we have seen how telecommunication began, the

basic components of a telecommunication system, how the need for expan-

sion of telecom services drove the world to develop manual and automatic

exchanges, and how they worked. Further proliferation of services led to the

development of long-distance telephony for intercity, interstate, and nally

international calls. The various media used for long-distance communica-

tion, the need for multiplexing, analog multiplexing principles and applica-

tions, and modern digital multiplexing technologies were discussed.

This chapter concerns the problem ...