Cathode Ray Tube (CRT):

Cathode Ray Tube (CRT):

Hey there, tech enthusiast, have you ever wondered how those old CRT monitors and TVs worked? You know, the bulky ones with the curved screens that were all the rage before flat panels took over. Cathode ray tube or CRT technology was behind it all, and despite being mostly obsolete today, it’s still fascinating to understand. In this article, we’ll explore how CRTs were able to take electronic signals and turn them into moving images right before our eyes.

We’ll go over how electron guns, phosphorescent screens, and high-voltage circuits all combined to make CRTs possible. Even though CRTs have gone the way of the dodo, their technology reminds us of how innovative the old days were. So sit back, relax, and get ready to dive into the technology behind those retro screens. This beginner’s guide to CRTs will have you seeing those old monitors and TVs in a whole new light.

Cathode Ray Tube (CRT):

What Is a Cathode Ray Tube?

A cathode ray tube or CRT is the technology behind those old chunky TVs and computer monitors. Simply put, it’s a vacuum tube that shoots streams of electrons across a screen to create images.

How CRTs Work

How CRTs Work

CRTs have three main parts:

  1. Electron gun – This shoots out beams of electrons. It The cathode is heated, causing electrons to boil off. The anode then accelerates and focuses them into a beam.
  2. Deflection plates – These metal plates bend and direct the electron beam, controlling where the beam strikes the screen. By manipulating the plates, the beam can be made to scan across and down the screen.
  3. Screen – The wide end of the tube is covered with a fluorescent screen that glows when struck by the electron beams. By aiming the beams at the right color phosphors, images and text are displayed.

CRTs were once king but fell out of favor due to their bulkiness, high energy needs and tendency to cause eye strain. Although obsolete, cathode ray tube technology paved the way for modern flat panel displays like LCDs and OLEDs that now dominate the market. Still, for those nostalgic for the warm glow of a CRT, a few specialty manufacturers continue making them for retro gamers and enthusiasts.

How Does a Cathode Ray Tube Work?

A cathode ray tube or CRT monitor contains millions of tiny parts, but how do they all come together to display an image on your screen?

How Does a Cathode Ray Tube Work?

At the back of the CRT, an electron gun shoots out a focused beam of electrons. This beam first passes through a mask with tiny holes that shapes it into the correct pattern.

Next, the beam is accelerated down the narrow neck of the tube by an anode. At the end of the tube, it hits the screen, which is coated with phosphorescent dots that glow when struck by electrons.

By controlling the electron beam, the CRT can illuminate certain dots and leave others dark, creating patterns that form images. But two more components are needed to produce a full color image:

  1. Shadow mask – A plate with holes that ensure each electron beam only strikes the correct color of dots.

The beam scans across the screen, illuminating the dots from left to right and top to bottom many times per second. By doing this repeatedly, the CRT can keep the image refreshed and prevent flickering. With the proper control and variation of the electron beams, photorealistic images and motion pictures can be displayed on the screen.

While cathode ray tube technology has mostly been replaced by LED and LCD screens, CRTs were pivotal in developing modern display technology and ushering in the age of television and computer monitors. Understanding how they work helps us appreciate all the engineering that went into creating the screens we now enjoy every day.

The Invention and History of the Cathode Ray Tube

The cathode ray tube or CRT was a pioneering technology that enabled the rise of televisions, computer monitors and other display devices for decades.

The Discovery of Cathode Rays

In the mid-1800s, scientists began experimenting with vacuumed tubes and noticed a glow emitted from the negative electrode or “cathode” when high voltage was applied. British scientist William Crookes investigated these mysterious “cathode rays” and found they traveled in straight lines, could cast shadows, and caused certain substances to fluoresce.

Crookes and others speculated these cathode rays were streams of negatively charged particles. This was confirmed in 1897 when J.J. Thomson measured the electron’s charge-to-mass ratio. We now know cathode rays are beams of electrons emitted by the cathode in a vacuum tube.

The Cathode Ray Tube is Born

Around the same time, German scientist Karl Ferdinand Braun created the first cathode ray tube. It was a vacuumed glass tube with a cathode that emitted electrons and a fluorescent screen that glowed when struck by the electron beam. By controlling the beam’s position with magnetic or electrostatic fields, a visible spot could be produced on the screen.

This was a breakthrough that enabled the first electronic display technologies. In the early 1900s, CRTs were used in some of the first oscilloscopes to visualize electronic signals. By the 1920s, CRTs were being developed for the earliest television prototypes. After WWII, CRT TVs and later CRT computer monitors became widely available, dominating the display market for decades.

Though CRTs have been superseded by flat-panel technologies like LCDs, we have cathode ray tubes to thank for pioneering the displays that shaped the 20th century. Their invention marked the first time humans could visually represent electronic signals and ultimately share information around the world.

Cathode Ray Tube Applications Over the Years

Cathode ray tubes (CRTs) have been used in many technologies over the decades. Early on, CRTs enabled some of the first television screens, computer monitors, and oscilloscopes.


The first commercially available televisions used CRTs to display images. CRT TVs were popular for decades until the early 2000s when flat-panel displays like LCDs and plasmas took over. CRT TVs produced bright, high-contrast images but were heavy, bulky, and consumed a lot of power.

Computer Monitors

CRT monitors were used with early desktop computers from the 1970s through the 1990s. Like CRT TVs, they produced crisp images but were large and cumbersome. As computers transitioned into homes and offices, the demand grew for smaller, lighter monitors. CRTs eventually gave way to LCD displays which were more compact and energy efficient.


CRTs had excellent performance for displaying waveforms and were ideal for use in oscilloscopes. Oscilloscopes with CRT displays were used by engineers and technicians to visualize and measure the waveform of electronic signals. They allowed the operator to view attributes like frequency, time intervals, voltage levels, and distortion.

Advantages and Disadvantages of CRT:

CRT displays have some advantages over newer display technologies, but also some significant drawbacks. Let’s look at the pros and cons of cathode ray tube monitors.

Pros of CRT Displays

CRT monitors produce great image quality with deep blacks and accurate color reproduction. They have wide viewing angles so the picture looks good even if you’re viewing the screen from the side. CRTs also have very fast response times which means less blurring for things like gaming or watching action movies.

Cons of CRT Displays

The biggest downside of CRTs is that they are bulky and heavy. The large cathode ray tube and associated electronics require a big, heavy enclosure. They also consume a lot of energy relative to modern display types like LCDs.

CRT monitors can suffer from image distortion and the screen may become curved over time. They are also more prone to flickering and the image can become permanently burned into the screen if the same static image is displayed for a long time.

While CRTs have benefits for certain uses like high-end color critical work or retro gaming, for most people the disadvantages outweigh the advantages. Modern flat panel display technologies like LCDs, LEDs and OLEDs provide many of the same benefits of CRTs without the bulk, weight and other issues. So, unless you have a specific need for a CRT, you’re probably better off with a newer display type.


And there you have it – a beginner’s guide to cathode ray tube technology. CRTs may be old tech, but they paved the way for modern display devices that power our TVs, phones, computers and more. Though bulkier than today’s sleek LCD and OLED screens, CRTs were instrumental in bringing images and information into our lives. Next time you’re watching your favorite shows or browsing online, take a second to appreciate how far display technology has come, and remember that it all started with a tube, some electrons, and a whole lot of innovation. You’ve now joined the ranks of those in the know about this historic display tech. Congratulations, you’re well on your way to becoming a display device expert! Keep learning and exploring; there’s a whole world of technology out there, just waiting to be discovered.

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