The study course is intended for power engineering students and is focused on signals theory aspects, required for power systems design, control and fault protection. Fourier and Laplace transforms are concerned both in continual and discrete form, as required by circuit steady state and transient analysis, application of numerical Laplace transform is taken in conjunction with network topological analysis. Resonant circuits are presented to form a basis, required to understand related overvoltage problems of high voltage networks. Numerical filtration is mostly limited to power systems protection applications, such as orthogonal components and symmetrical components filters. In the area of modulated signals basic modes (AM, FM, PM) and power line carrier applications are presented, pulse width modulations applications in power electronics is concerned to. Systems with feedback and their stability are presented. Hilbert’s transformation scope is limited by application for power control. Special aspects, related to polyphase networks, such as harmonics flow and modal transformations are specific to the study course.