What is cathode ray tube (CRT)? - Definition from WhatIs.com

Definition

cathode ray tube (CRT)

Part of the Electronics glossary:

A cathode ray tube (CRT) is a specialized vacuumtube in which images are produced when an electron beam strikes aphosphorescent surface. Most desktop computer displays make useof CRTs. The CRT in a computer display is similar to the"picture tube" in a television receiver.

A cathode ray tube consists of several basiccomponents, as illustrated below. The electron gun generates anarrow beam of electrons. The anodes accelerate the electrons.Deflecting coils produce an extremely low frequency electromagnetic field that allowsfor constant adjustment of the direction of the electron beam.There are two sets of deflecting coils: horizontal and vertical.(In the illustration, only one set of coils is shown forsimplicity.) The intensity of the beam can be varied. Theelectron beam produces a tiny, bright visible spot when itstrikes the phosphor-coated screen.

To produce an image on the screen, complexsignals are applied to the deflecting coils, and also to theapparatus that controls the intensity of the electron beam. Thiscauses the spot to race across the screen from right to left, andfrom top to bottom, in a sequence of horizontal lines called theraster. As viewed from the front of the CRT, the spot moves in apattern similar to the way your eyes move when you read asingle-column page of text. But the scanning takes place at sucha rapid rate that your eye sees a constant image over the entirescreen.

The illustration shows only one electron gun.This is typical of a monochrome, or single-color, CRT. However,virtually all CRTs today render color images. These devices havethree electron guns, one for the primary color red, one for theprimary color green, and one for the primary color blue. The CRTthus produces three overlapping images: one in red (R), one ingreen (G), and one in blue (B). This is the so-called RGB colormodel.

In computer systems, there are several display modes, or setsof specifications according to which the CRT operates. The mostcommon specification for CRT displays is known as SVGA (SuperVideo Graphics Array). Notebook computers typically use liquid crystal display.The technology for these displays is much different than that forCRTs.

This was last updated in September 2005
Posted by: Margaret Rouse

Related Terms

Definitions

  • signature analysis

    - Signature analysis has two meanings. It can involve scrutinizing human signatures in order to detect forgeries and it can be a troubleshooting technique in which an AC signal with a specific wavef... (WhatIs.com)

  • bioprinting

    - Although bioprinting is still in the experimental stage and is currently used primarily in scientific study rather than applied science, the possibility of creating functional replacement tissues o... (WhatIs.com)

  • flash storage

    - Flash storage, based on flash memory, is used for data repositories, storage systems and consumer devices, such as USB drives, smartphones and solid-state drives. Flash-based storage is faster than... (WhatIs.com)

Glossaries

  • Electronics

    - Terms related to electronics, including definitions about electrical components and words and phrases about computers, laptops parts, digital cameras, televisions and home appliances.

  • Internet applications

    - This WhatIs.com glossary contains terms related to Internet applications, including definitions about Software as a Service (SaaS) delivery models and words and phrases about web sites, e-commerce ...

Ask a Question About cathode ray tube (CRT)Powered by ITKnowledgeExchange.com

Get answers from your peers on your most technical challenges

Tech TalkComment

Share
Comments

    Results

    Contribute to the conversation

    All fields are required. Comments will appear at the bottom of the article.