Snapshot 1: lowpass filter, with the cutoff frequency
Snapshot 2: highpass filter, with the cutoff frequency
Snapshot 3: bandpass filter, centered at frequency and with width
For the lowpass and highpass filters, you specify the cutoff frequency ; for the bandpass filter, you specify the frequency that the passband is centered about and the width of the passband . Changing for the lowpass or highpass filters has no effect on the system, so the slider is disabled in those cases.