Introduction

The intent of this introduction is to give the reader an idea about Signals and Systems as a field of study and its applications. But we must first, at least vaguely define what signals and systems are.

   Signals are functions of one or more variables .

   Systems respond to an input signal by producing an output signal .

Examples of signals include :

1 . A voltage signal: voltage across two points varying as a function of time.
2 . A force pattern: force varying as a function of 2-dimensional space.
3 . A photograph: color and intensity as a function of 2-dimensional space.
4 . A video signal: color and intensity as a function of 2-dimensional space and time.

Examples of systems include :

1. An oscilloscope: takes in a voltage signal, outputs a 2-dimensional image characteristic of the voltage signal.
2. A computer monitor: inputs voltage pulses from the CPU and outputs a time varying display.
3 An accelerating mass : force as a function of time may be looked at as the input signal, and velocity as a function of time as the output signal.
4 A capacitance: terminal voltage signal may be looked at as the input, current signal as the output.