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2-35 In figure 2-32, observe the relative time for individual rf cycles. The time for each cycle is the same in views (A) and (B). Since this time is the same, we can assume that the carrier frequency is the same. But in view (C) the time for each cycle is about half that in views (A) and (B). Therefore, the frequency of the carrier in view (C) is nearly twice that of the other two. This illustration shows that carrier frequencies in pulse systems can vary. Figure 2-32A.—Carrier frequency. Figure 2-32B.—Carrier frequency. Figure 2-32C.—Carrier frequency. The carrier frequency is not the only frequency we must concern ourselves with in pulse systems. We must also be concerned with the frequency that is associated with the repetition rate of groups of pulses. Figure 2-33 shows that a specific time period exists between each group of rf pulses. This time is the same for each repetition of the pulse and is called the PULSE-REPETITION TIME (prt). To find out how often these groups of pulses occur, compute PULSE-REPETITION FREQUENCY (prf) using the formula: