This textbook explains the fundamentals of electric circuits and uses the transfer function as a tool to analyze circuits, systems, and filters. The author avoids the Fourier transform, since this topic is often not taught in circuits courses. General transfer functions for low pass, high pass, band pass and band reject filters are demonstrated, with first order and higher order filters explained in plain language. The author's presentation is designed to be accessible to a broad audience, with the concepts of circuit analysis explained in basic language, reinforced by numerous, solved examples.