the signal. Digital quantities on the other hand arerepresented by binary numbers (ONES and ZEROS).The binary ONES and ZEROS indicate the value at aparticular instant in time. Each bit position representsa portion of the overall quantity. The summation of thevalue of the set bits (ONES) is normally the quantity tobe represented. By setting or clearing particular bitpositions in the binary word, different values within aset of limits maybe expressed.ANALOG AND DIGITAL QUANTITYCOMPARISONSLet’s compare an analog quantity and a digitalquantity representing the same range of values, sayfrom 1 to 31 miles. The analog signal will be a linearsingle-phase ac sine wave. The ac signal is variablebetween 2 volts and 34 volts peak to peak. Anamplitude of 2 volts peak to peak will indicate 0 miles,the minimum limit value, and an amplitude of 34 voltswill indicate a value of 31 miles, the maximum limit.In this example, the increasing signal amplitudeindicates an increase in range in miles.The digital value will be expressed by five binarybits. Each bit position when set (a binary ONE)indicates a portion of the quantity. Bit 2^{0 }indicates avalue of 1 mile, bit 2^{1 }a value of 2 miles, bit 2^{2 }a valueof 4 miles, bit 2^{3 }a value of 8 miles, and bit 2^{4 }a valueof 16 miles. Zero miles is indicated when all bits areclear (binary ZEROs). The maximum of 31 miles isindicated when all bits are set (binary ONES), 31 milesbeing the sum of the value of all the set bits(1+2+4+8+16=31).Figure 13-1 shows the analog and digitalrepresentations of the same quantity through the rangeFigure 13-1.—Analog and digital quantity comparisons.13-2

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