3-3 Figure 3-2.—Square wave. One alternation is called a PULSE. The time for one complete cycle is called the PULSE-REPETITION TIME (prt). The number of times in 1 second that the cycle repeats itself is called the PULSE-REPETITION FREQUENCY (prf) or PULSE-REPETITION RATE (prr). If each alternation in figure 3-2 is 200 microseconds (µs), the prt will be 400 microseconds, and the prf will be 2,500 hertz. The following examples are provided to illustrate the mathematical relationship between prf and prt: You should readily see that prt is just the inverse of prf. Therefore: Given: