| CRT Monitors |
| A CRT monitor contains millions of tiny red, green, and blue phosphor dots that glow when struck by an electron beam that travels across the screen to create a visible image. The illustration below shows how this works inside a CRT. |
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| The terms anode and cathode are used in electronics as synonyms for positive and negative terminals. For example, you could refer to the positive terminal of a battery as the anode and the negative terminal as the cathode. |
| In a cathode ray tube, the "cathode" is a heated filament. The heated filament is in a vacuum created inside a glass "tube." The "ray" is a stream of electrons generated by an electron gun that naturally pour off a heated cathode into the vacuum. |
| Electrons are negative. The anode is positive, so it attracts the electrons pouring off the cathode. This screen is coated with phosphor, an organic material that glows when struck by the electron beam. |
| There are three ways to filter the electron beam in order to obtain the correct image on the monitor screen: shadow mask, aperture grill and slot mask. These technologies also impact the sharpness of the monitor's display. |
| Display History 101 |
| Displays have come a long way since the blinking green monitors in text-based computer systems of the 1970s. Just look at the advances made by IBM over the course of a decade: |
| • In 1981, IBM introduced the Color Graphics Adapter (CGA), which was capable of rendering four colors, and had a maximum resolution of 320 pixels horizontally by 200 pixels vertically. |
| • IBM introduced the Enhanced Graphics Adapter (EGA) display in 1984. EGA allowed up to 16 different colors and increased the resolution to 640x350 pixels, improving the appearance of the display and making it easier to read text. |
| • In 1987, IBM introduced the Video Graphics Array (VGA) display system. The VGA standard has a resolution of 640x480 pixels and some VGA monitors are still in use. |
| IBM introduced the Extended Graphics Array (XGA) display in 1990, offering 800x600 pixel resolution in true color (16.8 million colors) and 1,024x768 resolution in 65,536 colors. |
| CRT Features and Attributes | ||||||||||||||||||||||||
| To evaluate the specifications of CRT monitors, here are a few more things you need to know: | ||||||||||||||||||||||||
| Shadow-mask | ||||||||||||||||||||||||
| A shadow mask is a thin metal screen filled with very small holes. Three electron beams pass through the holes to focus on a single point on a CRT displays' phosphor surface. The shadow mask helps to control the electron beams so that the beams strike the correct phosphor at just the right intensity to create the desired colors and image on the display. The unwanted beams are blocked or "shadowed." | ||||||||||||||||||||||||
| Aperture-grill | ||||||||||||||||||||||||
| Monitors based on the Trinitron technology, which was pioneered by Sony, use an aperture-grill instead of a shadow-mask type of tube. The aperture grill consists of tiny vertical wires. Electron beams pass through the aperture grill to illuminate the phosphor on the faceplate. | ||||||||||||||||||||||||
| Most aperture-grill monitors have a flat faceplate and tend to represent a less distorted image over the entire surface of the display than the curved faceplate of a shadow-mask CRT. However, aperture-grill displays are normally more expensive. | ||||||||||||||||||||||||
| Slot-mask | ||||||||||||||||||||||||
| A less-common type of CRT display, a slot-mask tube uses a combination of the shadow-mask and aperture-grill technologies. Rather than the round perforations found in shadow-mask CRT displays, a slot-mask display uses vertically aligned slots. The design creates more brightness through increased electron transmissions combined with the arrangement of the phosphor dots. | ||||||||||||||||||||||||
| Dot pitch | ||||||||||||||||||||||||
| Dot pitch is an indicator of the sharpness of the displayed image. It is measured in millimeters (mm), and a smaller number means a sharper image. How you measure the dot pitch depends on the technology used: | ||||||||||||||||||||||||
| • In a shadow-mask CRT monitor, you measure dot pitch as the diagonal distance between two like-colored phosphors. Some manufacturers may also cite a horizontal dot pitch, which is the distance between two-like colored phosphors horizontally. | ||||||||||||||||||||||||
| • The dot pitch of an aperture-grill monitor is measured by the horizontal distance between two like-colored phosphors. It is also sometimes are called stripe pitch. | ||||||||||||||||||||||||
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| The smaller and closer the dots are to one another, the more realistic and detailed the picture appears. When the dots are farther apart, they become noticeable and make the image look grainier. | ||||||||||||||||||||||||
| Unfortunately, manufacturers are not always upfront about dot pitch measurements, and you cannot necessarily compare shadow-mask and aperture-grill CRT types, due to the difference in horizontal and vertical measurements. | ||||||||||||||||||||||||
| The dot pitch translates directly to the resolution on the screen. If you were to put a ruler up to the glass and measure an inch, you would see a certain number of dots, depending on the dot pitch. Here is a table that shows the number of dots per square centimeter and per square inch in each of these common dot pitches: | ||||||||||||||||||||||||
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| Refresh Rate | ||||||||||||||||||||||||
| In monitors based on CRT technology, the refresh rate is the number of times that the image on the display is drawn each second. If your CRT monitor has a refresh rate of 72 Hertz (Hz), then it cycles through all the pixels from top to bottom 72 times a second. | ||||||||||||||||||||||||
| Refresh rates are very important because they control flicker, and you want the refresh rate as high as possible. Too few cycles per second and you will notice a flickering, which can lead to headaches and eye strain. | ||||||||||||||||||||||||
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| Because your monitor's refresh rate depends on the number of rows it has to scan, it limits the maximum possible resolution. Most monitors support multiple refresh rates. Keep in mind that there is a tradeoff between flicker and resolution, and then pick what works best for you. | ||||||||||||||||||||||||
| This is especially important with larger monitors where flicker is more noticeable. Recommendations for refresh rate and resolution include 1280x1024 at 85 Hertz or 1600x1200 at 75 Hertz. | ||||||||||||||||||||||||
| Multiple Resolutions | ||||||||||||||||||||||||
| Because a CRT uses electron beams to create images on a phosphor screen, it supports the resolution that matches its physical dot (pixel) size as well as several lesser resolutions. For example, a display with a physical grid of 1280 rows by 1024 columns can obviously support a maximum resolution of 1280x1024 pixels. | ||||||||||||||||||||||||
| It also supports lower resolutions such as 1024x768, 800x600, and 640x480. As noted previously, an LCD monitor works well only at its native resolution. |
| LCDs vs. CRTs |
| If you are looking for a new display, you should consider the differences between CRT and LCD monitors. Choose the type of monitor that best serves your specific needs, the typical applications you use, and your budget. |
| Advantages of LCD Monitors |
| • Require less power - Power consumption varies greatly with different technologies. CRT displays are somewhat power-hungry, at about 100 watts for a typical 19-inch display. The average is about 45 watts for a 19-inch LCD display. LCDs also produce less heat. |
| • Smaller and weigh less - An LCD monitor is significantly thinner and lighter than a CRT monitor, typically weighing less than half as much. In addition, you can mount an LCD on an arm or a wall, which also takes up less desktop space. |
| • More adjustable - LCD displays are much more adjustable than CRT displays. With LCDs, you can adjust the tilt, height, swivel, and orientation from horizontal to vertical mode. As noted previously, you can also mount them on the wall or on an arm. |
| • Less eye strain - Because LCD displays turn each pixel off individually, they do not produce a flicker like CRT displays do. In addition, LCD displays do a better job of displaying text compared with CRT displays. |
| Advantages of CRT Monitors |
| • Less expensive - Although LCD monitor prices have decreased, comparable CRT displays still cost less. |
| • Better color representation - CRT displays have historically represented colors and different gradations of color more accurately than LCD displays. However, LCD displays are gaining ground in this area, especially with higher-end models that include color-calibration technology. |
| • More responsive - Historically, CRT monitors have had fewer problems with ghosting and blurring because they redrew the screen image faster than LCD monitors. Again, LCD manufacturers are improving on this with displays that have faster response times than they did in the past. |
| • Multiple resolutions - If you need to change your display's resolution for different applications, you are better off with a CRT monitor because LCD monitors don't handle multiple resolutions as well. |
| • More rugged - Although they are bigger and heavier than LCD displays, CRT displays are also less fragile and harder to damage. |
| So now that you know about LCD and CRT monitors, let's talk about how you can use two monitors at once. They say, "Two heads are better than one." Maybe the same is true of monitors! |
| Dual Monitors |
| One way to expand your computer's display is to add a second monitor. Using dual monitors can make you more productive and add a lot to your computing experience. |
| With two monitors, you can: |
| • View large spreadsheets |
| • Make changes to a web page's code on one monitor and view the results on the second |
| • Open two different applications, such as a Word document on one monitor and your web browser on the second |
| Besides two displays and two sets of the appropriate video cables, the only other thing you need is a video adapter with two display connections. The connections can be analog or digital; they need only to match the type of connections on the monitors. |
| It does not matter what type of monitor you use; two LCDs, two CRTs, or one of each works fine as long as the video adapter has compatible connections. |
| If you don't have a video adapter with two connections, you can purchase one and replace your current adapter. This generally works better than simply installing another video card with a single connection. Combination cards also come with more features, such as a TV-out port. |
| In addition to verifying your hardware, you should also double-check your computer's operating system to be sure it supports the use of dual monitors. For example, Windows 98 SE, Me, 2000, and XP support multiple monitors. |
| If you really want to increase your screen real estate, especially for applications such as financial trading or 3-D design, you can even implement three or more monitors. |
| Other Technologies |
| Touch-screen Monitors |
| Displays with touch-screen technology let you input information or navigate applications by touching the surface of the display. The technology can be implemented through a variety of methods, including infrared sensors, pressure-sensitive resistors or electronic capacitors. |
| Wireless Monitors |
| Similar in looks to a tablet PC, wireless monitors use technology such as 802.11b/g to connect to your computer without a cable. Most include buttons and controls for mousing and web surfing, and some also include keyboards. The displays are battery-powered and relatively lightweight. Most also include touch-screen capabilities. |
| Television and HDTV Integration |
| Some displays have built-in television tuners that you can use for viewing cable TV on your computer. You can also find displays that accept S-video input directly from a video device. Additional features include picture-in-picture or picture-on-picture capability, a remote control and support for high-definition television (HDTV). |