This document allows you to perform online Fourier filtering using an example of a signal consisting of two parts simulating pre-emergency and emergency modes. The pre-emergency mode is modeled by a sinusoidal signal, the emergency mode is modeled by a sinusoidal signal and an exponent. You can also perform online Fourier filtering for an arbitrary waveform from a waveform in the COMTRADE 1991 or 1999 format. You can see the essence of the Fourier transform here. Instructions for using the Fourier filter are given here.

**Please choose source of signal:**

Model signal

Oscillogram