Pulse-code modulation Variation in a signal that jumps sharply between two extremes Reclock The act of reasserting an original digital signal before too much degradation occurs 3.1 Data and Computers 55 Figure 3.2 An analog and a digital signal Threshhold Figure 3.3 Degradation of analog and digital signals information is lost. Since any voltage level within the range is valid, it’s impossible to know what the original signal state was or even that it changed at all. Digital signals, on the other hand, jump sharply between two extremes. This is referred to as pulse-code modulation (PCM). A digital signal can degrade quite a bit before any information is lost, because any voltage value above a certain threshold is considered a high value, and any value below that threshold is considered a low value. Periodically, a digital signal is reclocked to regain its original shape. As long as it is reclocked before too much degradation occurs, no information is lost. Figure 3.3 shows the degradation effects of analog and digital signals. Binary Representations
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