This is a filter passing specified band domain with use of FFT algorithm, enabling pass of frequency band domain what you want. It is very useful in selecting specific frequency band of signals and analyzing it.
Select data you want to apply this method in Analysis Window and click the icon of Band Pass FFT-Filtering in Analysis Tool Bar. This will display a dialogue box for frequency setting as shown in the below. Input frequency band domain as you want and click Apply button. Then, you can get results from pass of the specified frequency band in Display Window, which are registered at Analysis Window.