 recap (and I'll be brief), in this chapter we defined the words communication and telecommunication system. Next, I presented a whole gang of examples, to give you a feel for a few key communi- cation and telecommunication systems. Finally, we talked about analog and digital communications, discovering that most telecommunication engineers dream in digital. Meet you in Chapter 2! Introducing Telecommunications Problems 1. Briefly describe the following: (a) telecommunication system (b) communication system (c) the difference between a communication system and a telecommunication system. (d) digital communications (e) analog communications (f) the main reason why digital communications is preferred (to analog communications). 2. Describe the function of the following: (a) source coder (b) quantizer (c) sampler (d) symbol-to-bit mapper. Chapter Telecommunication Networks first, and always first, a definition. A telecommunication network is a telecommuni- cation system that allows many users to share information. 2.1 Telecommunication Network Basics 2.1.1 Connecting People with Telephones Let's say I have six people with telephones. I want to connect them together SO they can speak to one another. One easy way to connect everyone is to put copper wires everywhere. By that, I mean use a copper wire to connect person 1 to person 2, a wire to connect person 1 to person 3, ..., a wire to connect person 1 to person 6, ..., and a wire to connect person 5 to person 6. I've shown this solution in Figure 2.1. But, ugh, all these wires! In general, I need N(N-1), /2 wires, where N is the number of people. So with only six people I need 15 wires, with 100 people I need 49,950 wires, and with a million people I need 499,999,500,000 wires. Too many wires. Let's consider another way to connect users: put a switching center between the people, as Copper wire shown in Figure 2.2. The early switchboards worked like this: Gretchen picks up her phone to call Carl. A connection is immediately made to Mavis, a sweet elderly operator se