This app contains the all below topics in a very good and maintained ways. 1- Introduction of Signals and system 2- Classification of Signals 4- General Signal Characteristics 5- Operation on signals 6- Fundamentals of Systems 7- System properties 8- Linear Time Invariant System 9- Properties of LTI Systems, Casual systems 10- Fourier Representations 11- Frequency Response of LTI Systems 12- Fourier Transform representation for Periodic and discrete time Signals 13- Sampling 14- Reconstruction 15- Discrete Time Processing of Continuous Time Signals 16- Fourier Series representation for finite duration Nonperiodic signals 17- Modulation Types and Benefits 18- Full Amplitude Modulation 19- Pulse Amplitude Modulation 20- Multiplexing 21- Phase and Group delays 22- Representation of Signals using Continuous time Complex Exponentials: Laplace Transform 23- Unilateral Laplace Transform, its inversion 24- Laplace Transform Properties 25- Representation of Signals using Discrete time Complex Exponentials: The Z-Transform 26- Properties of Region of convergence 27- Inverse Z-Transform 28- Z-Transform Properties 29- Transform Analysis of LTI Systems