The book contains: Concept Introduction of Signals, Classification of Signals, General Signal Characteristics, Signal energy & Power, Continuous-Time Signals, Discrete-Time Signals Basic System Properties, Systems with and without memory, Invertibility, casuality, Stability, Time invariance, Linearity, Linear Time Invariant (LTI) Systems, Discrete Time LTI Systems, Convolution Representation of Linear Time-Invariant Discrete-Time Systems Convolution of Discrete-Time Signals Convolution Representation of Linear Time-Invariant Continuous-Time Systems Convolution of Continuous-Time Signals, Properties of LTI Systems, Casual systems. Fourier Representations for Signals: Representation of Discrete Time Periodic signals, Continuous Time Periodic Signals, Discrete Time Non Periodic Signals, Continuous Time Non-Periodic Signals, Properties of Fourier Representations, Frequency Response of LTI Systems, Fourier Transform representation for Periodic and discrete time Signals, Sampling, reconstruction, Discrete Time Processing of Continuous Time Signals, Fourier Series representation for finite duration Non-periodic signals.