Chapter 17 Summary: What Causes Them and What They Do to a Signal Reflections occur when the impedance of a transmission line changes for one reason or another, causing some of the energy in the electromagnetic field to be reflected back toward the source. This chapter provides details on how to calculate the amount of reflection and its polarity, and the difference between overshoot reflection and undershoot reflection. Readers will also develop an understanding of how to use termination resistors to manage upstream impedances and downstream impedances. Previous Chapter | Next Chapter