al; and (c) a digital signal Introducing Telecommunications 1.3.2 Definitions An analog communication system is a communication system where the information signal sent from point A to point B can only be described as an analog signal. An example of this is Monica speaking to Carl over the telephone, as described in Section 1.2.2. A digital communication system is a communication system where the information signal sent from A to B can be fully described as a digital signal. For example, con- sider Figure 1.6. Here, data is sent from one computer to another over a wire. The computer at point A is sending 0s or 1s to the computer at point B; a 0 is being repre- sented by -5 V for a duration of time T and a 1 is being represented by a +5 V for the same duration T. As I show in that figure, that sent signal can be fully described using a digital signal. Signal sent is: Can be represented by: Figure 1.6 A computer sending information to another computer Chapter One 1.3.3 And Digital Became the Favorite Digital communication systems are becoming, and in many ways have already be- come, the communication system of choice among us telecommunication folks. Certainly, one of the reasons for this is the rapid availability and low cost of digital components. But this reason is far from the full story. To explain the full benefits of a digital communication system, we'll use Figures 1.7 and 1.8 to help. Let's first consider an analog communication system, using Figure 1.7. Let's pretend the transmitter sends out the analog signal of Figure 1.7(a) from point A to point B. This signal travels across the channel, which adds some noise (an unwanted signal). The signal that arrives at the receiver now looks like Figure 1.7(b). Let's now consider a digital communication system with the help of Figure 1.8. Let's imagine that the transmitter sends out the signal of Figure 1.8(a). This signal travels across the channel, which adds a noise. The signal that arrives at the receiver is found in Figure 1.8 (b). Noise Figure 1.7 (a) Transm