TABLE OF CONTENTS This author believes that the most important communication service we have is the telephone. This is especially true since the development of cellular telephone systems. Conventional telephones are used not only for voice communication, but also for computer communications via modems, Internet access, fax transmissions, and other services. Additional discussion of cellular telephone systems is provided in Section 1.4. Much of the information presented in this chapter is quoted or adapted from [1] [2] [3] [4] [5] [6] [7] [8] [9] [10].
Figure 1.1 shows the main elements of a telephone system. On the left are the customer location and a number of telephone sets. The sets are connected by wire lines to a protector block. A single twisted pair of small-gauge wire known as the local loop connects each customer telephone system to a central office. Local loops from customers are combined in a cable. A typical cable has 1,400 pairs of copper wires carried in a single plastic-sheathed cable of about 3 inches in diameter.
The central offices or central switching center...
