CRO stands for:

Cathode Ray Oscilloscope (CRO)

CRO is a device that is used for the measurement of parameters of electrical quantities like frequency, amplitude, time period, and phase difference. 

Components of CRO:

1.) Electron Gun

• The electron gun is used to produce a narrow beam of electrons. It consists of a filament enclosed in a cylindrical cathode, a ring-shaped electrode called the control grid, and Two cylindrical anode electrodes known as the focusing anode and accelerating anode.
• The filament is heated when current flows through it. It is used to heat up the cathode.

2.) Deflection System

• The deflection system allows the electron beam to be deflected from its straight-line path when it leaves the electron gun.
• The deflection system consists of two sets of parallel plates. One set which is arranged vertically is known as X-plates and the other set which is arranged horizontally is known as Y-plates.

3.) Fluorescent Screen

• The fluorescent screen is coated on the inside surface with some fluorescent material such as phosphor or zinc sulfide.
• When electrons in the beam strike the screen, the material fluoresces and becomes luminous or glows. This enables a bright spot to appear wherever an electron beam strikes the screen.
• When these high-energy electrons strike the screen, the fluorescent coating on the screen converts the kinetic energy of the electrons into light energy.