This document provides an overview of cathode ray oscilloscopes (CROs). It discusses the basic components and workings of a CRO, including the electron gun assembly, deflection plates, and screen. It describes how multi-input oscilloscopes can have two or more input channels displayed in alternate or chopped mode. Lissajous patterns produced by two sinusoidal signals are also covered. Digital storage oscilloscopes are introduced, with key differences from analog storage oscilloscopes noted. Applications of CROs include frequency, amplitude, and phase measurement.