- The document is about signals and systems, a course taught by Tania Stathaki. - The course consists of 20-22 lectures over 9 parts of theory and 9 tutorial sheets. It is assessed solely by exam, with no coursework. - Signals refer to variations in physical states over time or space. Examples of signals include electrical, speech, images, physics, mechanics, astronomy, biomedicine, economics, and more. - Signals are classified as continuous or discrete time, analog or digital, periodic or aperiodic, causal/anticausal/noncausal, even/odd, deterministic or stochastic, finite or infinite length. Examples of different types of signals are provided.