This lecture covers the Fourier transformation, definition of the sign function, and the Dirac pulse train. It delves into the properties of the sign function, its Fourier transformation, and the application of scaling the Dirac pulse. The lecture also explores the development in series of Fourier, convergence of the Fourier series, and periodization with a Dirac comb. Additionally, it discusses the interpretation of Fourier series, convolutional shift, and the synthesis of a periodic signal using simple generators.