An impulse input, as shown in Figure 3-1, to a dynamic system is defineddifferently depending on whether the system is discrete or continuous. Fora continuous dynamic system, an impulse input is a unit-area signal with aninfinite amplitude and infinitely small duration occurring at a specifiedtime. At all other times, the input signal value is zero. For a discrete system,an impulse is a physical pulse that has unit amplitude at the first sampleperiod and zero amplitude for all other times.