Introduction to Signal Information converted into an electrical form suitable for transmission is called a signal.  Schaum Series on Signals and systems states that A signal is a function representing a physical quantity or variable, and typically it contains information about the behaviour or nature of the phenomenon. For instance, in a RC circuit the signal may represent the voltage across the capacitor or the current through the resistor. Mathematically, a signal is represented aas a function of an independent variable ‘t’. Usually t represent time. Thus a signal is denoted by x(t). Types of Signals: Continuous vs discrete signals Analogvs digital signals Real vs complex signals Deterministic vs Random signals Even vs Odd Signals Continuous vs Discrete Signals Continuous Signal Discrete Signal A signal is  continuous-time