The concepts of signals and systems appear in a wide variety of fields. The physical nature of the signals to be acquired and the measurement systems may differ from application to application, but they all have in common that the signals contain information about the observed phenomenon and secondly, the systems respond to particular signals by producing other signals or certain behavior as output. This course discusses how to characterize a linear time-invariant system and how it will respond to various inputs. The unit impulse response or - its equivalent in the frequency domain - the frequency response characterizes a linear time-invariant system. This course discusses convolution. The Fourier series representation and the Fourier transform with their properties are introduced. The Laplace transform and Z-transform generalize the Fourier transform for continuous-time and discrete-time systems, respectively. Techniques for sampling and reconstruction of sampled signals are discussed. Furthermore, the course focuses on how to design systems to process signals in particular ways, that is filtering techniques. Besides signal enhancement and signal restoration, the course looks into the design of systems to extract specific pieces of information from signals. Finally, the course discusses the design of systems that allow for modifying or controlling the characteristics of another system.