You may have heard the term “CRT,” and you might know that it has something to do with TVs, monitors, video games, or computers, but what does “CRT” actually mean? We’ll explain.
What Is a CRT?
In the context of electronics, CRT stands for “cathode ray tube.” It’s a technical term for the glass picture tube inside of a vintage TV set or computer monitor—the kind used before flat-screen displays became common. CRTs are electronic image display devices that have the advantage of showing information dynamically without the need for moving parts.
When someone says “a CRT,” they might also be referring to a TV set or monitor that uses a CRT instead of the actual cathode ray tube itself.
Why “cathode ray?” Before the discovery of the electron, scientists called streams of electrons “cathode rays,” because these mysterious rays were first seen being emitted by a cathode (a negatively charged electrode), casting shadows inside a vacuum tube. In 1897, a German engineer named Karl Ferdinand Braun added a phosphorescent screen and magnetic deflection control to create the first cathode ray tube, which he used to display the waveform of AC current like an oscilloscope.
Over time, other scientists discovered that CRTs could be used to display moving images without the need for mechanical moving parts, providing a key element to the commercialization of television. Later, computers began to use CRT monitors as output devices as well, making them more interactive and eliminating the need for continuous printed paper output.
How Do CRTs Work?
CRTs are sealed glass vacuum tubes that contain three major components: an electron source (often called an electron gun), an electromagnetic deflection system (that steers the electron beam), and a phosphorescent screen that glows when hit by the electron beam.
In the case of a color CRT display, there are three electron guns: one each for red, green, and blue, and they are aimed at colored phosphors that glow with those colors when hit by the corresponding beams. The intensity of the beam can be modulated as well, which changes the brightness in certain parts of the image.
CRT televisions and most CRT computer monitors draw an image on the screen line by line, from top to bottom, in a raster pattern, 30 or 60 times a second. This is called a raster display. Other CRTs, such as those used in oscilloscopes and insome early arcade video games, directly plot an image by tracing lines on the phosphor screen with a single electron gun, more like an electronic Etch-A-Sketch. These are called vector displays.
Obviously, we’re just simplifying things here. CRTs need a lot of additional supporting circuitry, such as a power supply and logic to receive and generate the image signals that will be displayed on the screen. Those components vary by display size, type, and manufacturer.
Why Don’t We Use CRTs Anymore?
Sure, some people still use CRTs for specialized cases—including for legacy electronics (such as in some older airplane cockpits) and for retro gaming—but otherwise, the CRT’s time has come and gone.
CRTs were most popular between the 1950s and the mid-2000s, first in television sets and then in computer monitors as well. In the United States, commercial CRT television production ceased largely in the mid-2000s, with some holdouts continuing into the 2010s. Today, a few specialized firms still make or refurbish CRTs, but largely for non-consumer markets.
Most people don’t use CRTs anymore because flat-screen display technology (led largely by LCDs) has significant commercial and physical advantages. In general, flat-screen displays are cheaper to manufacture, are lighter and thinner, use less electricity, and produce less heat than CRT displays. They also provide opportunities for digital sharpness, clarity, and resolution far beyond that of a CRT display, and flat screens can be manufactured in much larger screen sizes than CRTs.
Are There Any Advantages to CRTs?
In the 2000s and 2010s, CRTs still offered advantages over flat-panel technologies in some categories, such as better color richness, better response time, and better multi-sync resolution support, but recent advances in flat-screen tech have closed most of those gaps.
Still, there are people who prefer CRTs for vintage computer and video-gaming applications, since CRTs were the intended display technologies in use at the time. There are three main reasons why CRTs are often better than flat-panel displays for retrogaming.
The first reason is that CRTs handle the odd, non-standard display resolutions of old game consoles better than modern digital displays. When used with modern HDTVs, old game console graphics can look stretched, washed out, jagged, or blurry. But when viewed on a vintage CRT, everything is crisp and correctly proportioned.
Second, some video game accessories, such as light guns, only work with CRT displays. You can’t play Nintendo’s Duck Hunt on an HDTV with an original light gun, because the technology works in perfect synchronization with a CRT’s video signal timing.
Third, the visual artifacts created when images are displayed on a CRT can be considered part of the original intended art style of some video games. In fact, some games took advantage of the properties of an NTSC signal or the CRT itself to blend colors or provide the illusion of more depth, shading, and transparency than would be the case on a pixel-perfect display. (For excellent examples of this, check out this deep thread on Twitter.)
Most of those positive graphical artifacts are lost when modern games are presented in pixel-perfect formats through emulators or on modern digital displays. You’ll lose the blending of colors, and the aspect ratio might be off as well, since not all pixels were intended to be square.
With CRTs on the endangered species list, there is some fear that we may lose touch with this important 20th-century technology for good. But when it comes to supposedly obsolete technology, don’t count anything out forever. Just look at the success of vinyl and the Impossible Project, which brought Polaroid instant film back into production.
Some day, we may see the rise of CRTs again for boutique applications, but until then, it’s up to today’s technicians to keep examples of this culturally important display technology alive so that future generations can see how it worked for themselves.