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CRT Monitors


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crt monitor Are you wondering how all those colors are displayed on your CRT computer monitor?  In a nutshell, dots of red, blue, and green chemicals blend into millions of colors and end up as the graphics you see on your screen.  Via something called a "bitmap," the colors are arranged and mapped out in terms of position, size, and color.  While there are several ways of doing it, one of the most common ways of storing and displaying bitmaps is through a CRT — or cathode-ray tube — monitor.

How do these monitors work?  To begin with, signals from either operating system or application software are sent to something called the super video graphics array adapter (SVGA).  This adapter then sends the signal through a digital-to-analog converter (DAC) circuit.  This circuit is usually comprised of three DACs, each of which is assigned to either red, blue, or green.

The DAC then decides, by using a conversion table, the voltage levels for each of the three primary colors that are needed to create the color in a display pixel.

Next, the adapter sends its message to three electron guns that represent each of the three primary colors.  These guns are located in the monitor's CRT, which is how the monitor gets its name.  Based on the signal, each gun sends out a stream of electrons in a certain intensity.

But how do the electrons know where to go?  Well, the display adapter communicates with a device in the monitor — a magnetic deflection yoke — that aims the stream.  The signals sent will not only determine the resolution, which is the number of pixels displayed, but will also determine how often the image on the screen is refreshed.

The sharpness of the image depends upon the monitor's dot pitch, which is the screen through which the beams pass through.  The closer the dots on the screen, the clearer the image that appears on your monitor.

Once the beams pass through the dot screen, they hit a phosphor coating on the inside of the screen.  The phosphors, which glow when they are hit by the electrons, are specific to each color.  The intensity of the beam affects the amount of light the phosphor emits.  The colorful image that ends up on the monitor depends upon the combination of the beams and their different intensities.

Once the color sweeps horizontally across the screen, the process starts all over again and the image is redrawn.  Of course, you can't see this with the naked eye because it happens too quickly.  Most CRT screens are refreshed about 60 times per second!

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CRT Computer Monitors - LCD Computer Monitors

old crt monitor ready for recycling
Old CRT Monitor Being Recycled