The square wave Fourier series provides fundamental insight into the nature of Fourier series expansions. You will learn the relationship between the width or duty cycle of a square wave and the concentration of the Fourier series coefficients. You will also be introduced to the sinc function, a function that has widespread significance in all forms of Fourier analysis. You will encounter both the square wave and sinc function repeatedly in your signal-processing studies. Developing your insight and understanding of the square wave Fourier series and the sinc function will pay dividends as you work in this field.