The reader is provided with essential knowledge of basic electronic circuits. A systematic presentation and clarity are prioritized. The functioning and application possibilities of circuits are illustrated with practical examples. Although primarily designed as a supplementary learning tool for schools and training courses, self-study is easily feasible. The oscilloscope as a versatile measuring instrument, rectifier circuits, amplifier circuits, circuits for stabilizing voltages and currents, transistor switching stages, circuits with multilayer diodes, Diac and Triac, flip-flop circuits, generator and pulse shaping circuits, fundamentals of control engineering, introduction to digital technology, digital codes/digital counting and storage technology.