Figure 3-3.Input signals 180º out of phase.
The circuit and the input and output signals are shown at the top of the figure. The lower portion of
the figure is a comparison of the input signals and the output signal. Notice the vertical lines marked "T0"
through "T8." These represent "time zero" through "time eight." In other words, these lines provide a way
to examine the two input signals and the output signal at various instants of time.