. For the quantization process, we want to present to the coder a discrete voltage value. Suppose our quantization steps were in 0.1-V increments and our voltage measure for one sample was 0.37 V. That would have to be rounded off to 0.4 V, the nearest discrete value. Note here that there is a 0.03-V error, the difference between 0.37 V and 0.40 V. Figure 6.3 shows one cycle of the PAM wave appearing in Figure 6.1, where we use a 4-bit code. In the figure a 4-bit code is used that allows 16 different binary-coded possibilities or levels between +1 V and -1 V. Thus we can assign eight possibilities Range 0 standard values 3 141515 15 14 14 12 1110 Coded values Figure 6.3 Quantization and resulting coding using 16 quantizing steps. DIGITAL NETWORKS above the origin and eight possibilities below the origin. These 16 quantum steps are coded as follows: Number Number Examining Figure 6.3 shows that step 12 is used twice. Neither time it is used is it the true value of the impinging sinusoid voltage. It is a rounded-off value. These rounded-off values are shown with the dashed lines in Figure 6.3, which follows the general outline of the sinusoid. The horizontal dashed lines show the point where the quantum changes to the next higher or lower level if the sinusoid curve is above or below that value. Take step 14 in the curve, for example. The curve, dropping from its maximum, is given two values of 14 consecutively. For the first, the curve resides above 14, and for the second, below. That error, in the case of 14, from the quantum value to the true value is called quantizing distortion. This distortion is a major source of imperfection in PCM systems. Let's set this discussion aside for a moment and consider a historical analogy. One of my daughters was having trouble with short division in school. Of course, her Dad was there to help. Divide 4 into 13. The answer is 3 with a remainder. Divide 5 into 22 and the answer is 4 with a remainder. Of course, she would tell what the remainders were. But for you, the reader, I