This document discusses control systems and Bode diagrams. It includes: 1. An outline of the document with sections on frequency response and an introduction to Bode diagrams. 2. Descriptions of how frequency response is used to analyze systems and determine stability. It also describes how sinusoidal inputs produce harmonic outputs. 3. An introduction to Bode diagrams including how they were developed and that they consist of magnitude and phase plots versus log frequency. Bode diagrams provide a standard way to represent frequency response.