 of discrete values: any small fluctuation of the signal is important. Radio waves are analog, as are power waves. Sound is also analog. When you speak, you create waves of air that hit people's eardrums. The sound waves are an analog signal. Chapter 20: Telecom Nomenclature Digital refers to a signal that has discrete values. If you analyze a sound wave, and then assign a value to each sample of the wave at specific time intervals, you will create a digital representation of the analog wave. Because digital involves discrete values and analog does not, converting analog signals to digital will always result in loss of information. While increasing the rate at which the signal is sampled (among other things) can increase the quality of the final reproduction, technically, the signal cannot be reproduced exactly the same way. Bandwidth Bandwidth is one of those terms that is thrown around a lot by people who don't really know what it means. A range of frequencies is called a band. The width of the band is referred to as bandwidth. For those of you who aren't old enough to remember FM radios with analog dials, I've drawn one in Figure 20-1. 2 MHz FM radio dial 20 MHz Figure 20-1. True bandwidth example An FM radio dial displays the range of frequencies allocated by the US government for stereo radio broadcasts. The exact range of frequencies is 87.9 MHz to 107.9 MHz. The bandwidth of this range is 20 MHz. The frequency range of 90 MHz to 92 MHz inclusive has a bandwidth of 2 MHz. What we're really referring to when we talk about bandwidth on digital links is the throughput. On a digital link, the number of possible state transitions per second is how we measure throughput. Figure 20-2 shows how the number of state transitions can vary based on link speed. The signal on the left shows six possible state changes in the time depicted. Two concurrent equal values do not require a change of state, SO only five state changes occurred, though six were possible. The signal on the right shows 19 pos- sible state changes in 