ABSTRACT
A signal processing system is a functional unit with one or more inputs to which we can supply signals, and one or more outputs where we can take off signals. An example of such a system is the harmonic oscillator that we got to know in chapter 3. In this chapter we will deal in the first place with the general properties of systems and we will treat the system as a ‘black box’ because we are only interested in the relation between the output and the input signals. Later in this chapter and particularly in the next chapter the ‘inside’ will be dealt with.
