This unique compendium consists of two parts - electric circuit and fundamentals of transmission theory. The first part contains all the necessary materials to understand electric circuit and emphasizes on numerical method and calculation using Python program. The crucial second part starts with Maxwell equations to treat the electromagnetic phenomena of conducting materials and derives the Heaviside equation for transmission theory in distributed-parameter circuit. Boundary condition of the lumped and distributed circuits are introduced. The boundary condition enables readers to understand the source of electric noise from circuit.This useful reference text will benefit researchers, professionals, engineers, advanced undergraduate and graduate students in the field of circuits & systems.