The three-volume introduction helps to understand electrical engineering as a cohesive field that can be described according to unified principles. Volume 3 expands network knowledge to time-varying processes, of which alternating current technology serves as an important technical foundation of electrical engineering. Furthermore, it provides the basis for transforming the network through transformations (Fourier, Laplace) into a more abstract system perspective, leading to continuous-time systems. These are essential as the foundation of digital signal processing. The fundamental knowledge required for this is provided.