As an illustration of a general method for calculating the circuit response of a network subjected to a periodic signal, the case of an RC circuit driven by a square-wave generator is worked out in complete detail for three values of a circuit parameter. A computer is used to add a sufficient number of Fourier sinusoidal terms and to plot out the circuit response. A criterion for the number of terms needed is given. For comparison, the exact solution is also presented. Experimental verification is achieved by photographing the screen of an oscilloscope which is connected across the proper circuit element. The resulting photographs are enlarged (in effect) to the exact size of the computer plots onto transparent film. An overlay of the transparencies on the computer plots give excellent agreement.