ELEC 320
Prof. Rich Kozick

## Classes of Systems:

1. Linear and nonlinear systems

2. Constant-parameter (time-invariant) and time-varying-parameter (time-varying) systems

3. Instantaneous (memoryless or static) and dynamic (with memory) systems

4. Causal and noncausal systems

5. Lumped-parameter and distributed-parameter systems

6. Continuous-time and discrete-time systems

7. Analog and digital systems
These are the most common and important classes of systems.

Exercises:

1. Consider a system that plays an audio tape at half-speed. Let x(t) represent the audio signal at full-speed, and y(t) be the output signal from the half-speed system. Assume x(t) begins at time t=0 and is defined for t>0.

• Can the system be modeled as y(t) = x(2t), or y(t) = x(t/2), or neither?
• Is the system linear? Is it time-invariant? Is it causal? Please explain.

2. For each of the following system classification properties, try to think of at least one example of a system with that property.

Linear, nonlinear, time-invariant, time-varying, memoryless, with memory, causal, non-causal.