. The Bell System technical journal. Telecommunication; Electric engineering; Communication; Electronics; Science; Technology. 560 BELL SYSTEM TECHNICAL JOURNAL in intensity with distance. The distance between successive maxima, or the wave-length, will vary inversely with the frequency of the applied alternating current. Figure 7 shows such a record of a speech wave and of sinusoidal waves of two different frequencies. The variations are superposed on a uniform component so as to avoid the difficulty of negative Fig. 7 The frequency of an alternating current is defined as the number o
. The Bell System technical journal. Telecommunication; Electric engineering; Communication; Electronics; Science; Technology. 560 BELL SYSTEM TECHNICAL JOURNAL in intensity with distance. The distance between successive maxima, or the wave-length, will vary inversely with the frequency of the applied alternating current. Figure 7 shows such a record of a speech wave and of sinusoidal waves of two different frequencies. The variations are superposed on a uniform component so as to avoid the difficulty of negative Fig. 7 The frequency of an alternating current is defined as the number of complete cycles which it executes in unit time. The analog of frequency in the corresponding alternating space wave is therefore the number of complete cycles or waves executed in unit distance. This is the reciprocal of the wave-length just as the frequency is the reciprocal of the period. Inasmuch as the term wave-number has been used by physicists to designate the reciprocal of wave-length, I shall use that term to designate the quantity corresponding to frequency in the steady state analysis of a magnitude-distance function. The distortion suffered by a picture in transmission may therefore be expressed in terms of the steady state amplitude and phase distortions as functions of wave number. Just as the transmission of a given amount of information requires a given product of frequency-range by time, so the preservation of a given amount of information in a picture requires a corresponding product of wave-number-range by distance. To illustrate, consider the effect of enlarging a picture without changing its detail or fineness of intensity discrimination. Suppose the enlargement to be made in two steps. In the first the. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original American Telephone and Telegraph C
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Keywords: ., bookcentury1900, bookdecade1920, booksubjecttechnology, bookyear1
