Computer Monitors Seeing , Hearing , and Printing Data || Video & Sound Monitors

Introduction Reaching Our Senses with Sight and Sound In the beginning, computing was anything but a feast for the senses. The earliest computers were little more than gigantic calculators controlled by large panels of switches, dials, and buttons. Today, nearly every computer features some kind of visual display, but display screens were uncommon until the 1960s. Now, computers can communicate information to you in several ways, but the most exciting types of output are those that appeal to the senses. It is one thing to read text on a printed page, but it is very different to see a document take shape before your eyes. It can be very exciting to watch moving, three-dimensional images on a large, colorful screen while listening to sounds in stereo. Modern display and sound systems make the computing experience a more inviting one. Because of these sophisticated output technologies, computers are easier to use, data is easier to manage, and information is easier to access. These technologies enable us to play games and watch movies, experience multimedia events, and use the PC as a communications tool. This lesson introduces you to monitors and sound systems. You will learn about the different types of monitors commonly used with computers and how they work. You also will learn some important criteria for judging a monitor's performance. This les- son also shows you how computers can output sounds.

What is Monitors The keyboard is the most commonly used input device and the monitor is the most commonly used output device on most personal computer systems. As you use your computer-whether you are typing a letter, copying files, or surfing the Internet-hardly a moment goes by when you are not looking at your monitor. In fact, people often form an opinion about a computer just by looking at the monitor. They want to see whether the image is crisp and clear and how well graphics are displayed on the monitor. Two important hardware devices determine the quality of the image you see on any monitor: the monitor itself and the video controller. In the following sections, you will learn about both of these devices in detail and find out how they work together to display text and graphics. In general, two types of monitors are used with PCs. The first is the typical monitor that comes with most desktop computers, it looks a lot like a television screen and works in much the same way. This type of monitor uses a large vacuum tube, called a carded ray tube (CRT). The second type, known as a flat panel display, was used primarily with portable computers in the past. Today, flat-panel monitors are a popular feature with desktop computers. All monitors can be categorized by the way they display colors: Monochrome monitors display only one color (such as green, amber, or white) against a contrasting background, which is usually black. These monitors are used for text-only displays where the user does not need to see color graphics. Grayscale memes display varying intensities of gray (from a very light gray to black) against a white or off-white background and are essentially a type of monochrome monitor. Grayscale flat-panel displays are used in low-end portable systems-especially handheld computers-to keep costs down. (color monitors can display between 16 colors and 16 million colors. Today, most new monitors display in color. Many color monitors can be set to work in monochrome or grayscale mode.

What is CRT Monitors The typical CRT monitor works. Near the back of a monitor's housing is an electron gun, The gun shoots a beam of electrons through a magnetic coil (sometimes called a yoke), which aims the beam at the front of the monitor. The back of the monitor's screen is coated with phosphors, chemicals that glow. when they are struck by the electron beam. The screen's phosphor coating is organized into a end of dots. The smallest number of phosphor dots that the gun can focus on is called a prel, a contraction of the term picture element. Each pixel has a unique address, which the computer uses to locate the pixel and control its appearance.  Some electron guns can focus on pixels as small as a single phosphor dot. Actually, the electron gun does not just focus on a spot and shoot electrons at it. It systematically aims at every pixel on the screen, starting at the top left corner and scanning to the right edge. Then it drops down a tiny distance and scans another line. Like human eyes reading the letters on a page, the electron beam follows each line of pixels across the screen until it reaches the bottom of the screen. Then it starts over. As the electron gun scans, the circuitry driving the monitor adjusts the intensity of each beam In a monochrome monitor, the beam's intensity deter mines whether a pixel is on (white) or off (black). In the case of a grayscale monitor, the beam's intensity determines how brightly each pixel glows A color monitor works like a monochrome one, except that there are three electron beams instead of one. The three guns represent the primary additive colors (red, green, and blue), although the beams they emit are colorless.  Ina color monitor, each pixel includes three phosphors-red, green, and blue arranged in a triangle. When the beams of each of these guns are combined and focused on a pixel, the phosphors light up. The monitor can display different colors by combining various intensities of the three beams.

What's Inside A Computer Program System

One pixel A CRT monitor contains a shadow mask, which is a fine mesh made of metal, fitted to the shape and size of the screen. The holes in the shadow mask's mesh are used to align the electron beams, to ensure that they strike precisely the correct phosphor dot. In most shadow masks, these holes are arranged in triangles. CRT monitors have long been the standard for use with desktop computers because they provide a bright, clear picture at a relatively low cost. There are two major disadvantages, however, associated with CRT monitors: Because CRT monitors are big, they take up desktop space and can be difficult to move. A standard CRT monitor may be more than 16 inches deep and weigh about 30 pounds. (A new breed of "thin" CRTs is significantly thinner and lighter than old-fashioned CRT monitors, but they are still relatively deep and heavy.) By contrast, flat-panel monitors are gaining popularity because they are only a few inches deep and usually weigh less than 10 pounds. CRT monitors require a lot of power to run; therefore, they are not practical for use with notebook computers. Instead, notebook computers use flat-panel monitors that are less than one-half-inch thick and can run on battery power that is built into the computer.

How Does A Computer Program Process Input From A Keyboard And Mouse?

What is Flat-Panel Monitors Although flat-panel monitors have been used primarily on portable computers, new generation of large, high-resolution, flat-panel displays is gaining popularity among users of desktop systems. These new monitors provide the same viewable area as CRT monitors, but they take up less desk space run cooler than traditional CRT monitors.  There are several types of flat-panel monitors, but the most common is the liquid crystal display (LCD)monitor. The LCD monitor creates images with a special kind of liquid crystal that is normally transparent but becomes opaque when charged with electricity.  One disadvantage of LCD monitors is that their images can be difficult to see in bright light. For this reason, laptop com purer users often look for shady places to sit when working outdoors or near windows. A bigger disadvantage of LCD monitors, however, is their limited viewing angle-that is, the angle from which the display's image can be viewed clearly. With most CRT monitors, you can see the image clearly even when standing at an angle to the screen. In LCD monitors, however, the viewing angle shrinks; as you increase your angle to the screen, the image becomes fuzzy quickly. In many older flat-panel systems, the user must face the screen nearly straight on to see the image clearly. Technological improvements have extended the viewing angles of flat-panel monitors. There are two main categories of liquid crystal displays: The passive main LCD relies on transistors for each row and each column of pixels, thus creating a grid that defines the location of each pixel. The color displayed by a pixel is determined by the electricity coming from the transistors at the end of the row and the top of the column. Although passive matrix monitors are inexpensive to manufacture, they have a narro viewing angle. Another disadvantage is that they don't "refresh" the pixels very quickly. (Refresh rate is described in more detail later in this lesson.) If you move the pointer too quickly, it seems to disappear, an effect known as submarining. Animated graphics can appear blurry on a passive matrix monitor. Most passive matrix screens now use dual-scan LCD technology, which scans the pixels twice as often. Submarining and blurry graphics are less troublesome than they were before the dual-scan technique was developed. The active matrix LCD technology assigns a transistor to each pixel, and each pixel is turned on and off individually. This enhancement allows the pixels to be refreshed much more rapidly, so submarining is not a problem Active matrix screens have a wider viewing angle than passive matrix screens. Active matrix displays use thin-film transistor (TFT) technology, which employs as many as four transistors per pixel. Today, most note- book computers feature TFT displays.

Importance Program Of Computer In Today Era

Other Types of Monitors While CRT and flat-panel monitors are the most frequently used types of displays in PC systems, there are other kinds of monitors. These displays use specialized technologies and have specific uses: Paper-white displays are sometimes used by document designers such as desktop publishing slim ageists, newspaper or magazine compositors, and other persons who create high-quality printed documents. A paper-white display produces a very high contrast between the monitor's white background and dis played text or graphics, which usually appear in black. An LCD version of the paper-white display is called a page white display. Page-white displays unlike a special technology, called supertwist, to create higher contrasts. Electroluminescent displays (CLDs) are similar to LCD monitors but use a phosphorescent film held between two sheets of glass. A grid of wires sends current through the film to create an image. Plasma displays are created by sandwiching a special gas (such as neon or xenon) between two sheets of glass. When the gas is electrified via a grid of small electrodes, it glows. By controlling the amount of voltage applied at various points on the grid, each point acts as a pixel to display an image.

What is Comparing Monitors If you need to buy a monitor, go comparison shopping before making a purchase. Look for a monitor that displays graphics nicely and is easy on your eyes, allowing you to work longer and more comfortably A poor monitor can reduce your productivity and may even contribute to eyestrain. When shopping for a monitor, first look at a screen full of text and examine the crispness of the letters, especially near the corners of the screen. In standard CRT monitors, the surface of the screen is curved, causing some distortion around the edges and especially in the corners. In some low-cost monitors, this distortion can be bothersome. Thin CRT displays have flat screens so, like flat-panel LCD monitors, they eliminate this problem. Next, display a picture with which you are familiar and see whether the colors look accurate. If possible, spend some time surfing the World Wide Web to display different types of pages. Even if the monitor looks good (or if you are buying it through the mail), you need to check several specifications. The following are the most important: Size Resolution Refresh rate Dot pitch Monitors Size A monitor's size affects how well you can see images. With a larger monitor, you can make the objects on the screen appear bigger, or you can fit more of them on the screen. Monitors are measured diagonally, in inches, across the front of the screen. A 17-inch monitor measures 17 inches from the lower left to the upper right corner. However, a CRT monitor's actual viewing arahant is, the portion of the monitor that actually displays images-is smaller than the monitor's overall size. The viewing area of a flat-panel display will be somewhat larger than the viewing area of a comparably sized CRT monitor. As a rule of thumb, buy the largest monitor you can afford.

Computer Programming Language

Monitors Resolution The term resolution refers to the sharpness or clarity of an image. A monitor's resolution is determined by the number of pixels on the screen, expressed as a matrix. The more pixels a monitor can display, the higher its resolution and the clearer its images appear. For example, a resolution of 640 × 480 means that there are 640 pixels horizontally across the screen and 480 pixels vertically down the screen. Because the actual resolution is determined by the video controller- not by the monitor itself-most monitors can operate at several different resolutions. The five commonly used resolution settings: (a) 640 x 480, (b) 800\times600 (c) 1024\times768. (d) 1152\times864 and (e) 1280\times1024 Note that, as the resolution increases, the image on the screen gets. There are various standards for monitor resolution. The Video Graphics Array (VGA) standard is 640\times480 pixels. The Super VGA (SVGA) standard expanded the resolutions to 800\times600 and 1024\times768 Today, nearly any color monitor can be set to even higher resolutions. Higher settings are not always better, how- ever, because they can cause objects on the screen to appear too small, resulting in eyestrain and squinting. Compare the two screens shown in. Both were taken from the same 17-inch monitor. The first image is displayed at 640×480 resolution, the second image shows the same screen at 1280 × 1024.

Monitors Refresh Rate A monitor's refresh rate is the number of times per second that the electron guns scan every pixel on the screen (). Refresh rate is important be- cause (b) 800\times600 (c) 1024\times768. (d) 1152\times864 and (e) 1280\times1024 Note that, as the resolution increases, the image on the screen gets. There are various standards for monitor resolution. The Video Graphics Array (VGA) standard is 640\times480 pixels. The Super VGA (SVGA) standard expanded the resolutions to 800\times600 and 1024\times768 Today, nearly any color monitor can be set to even higher resolutions. Higher settings are not always better, how- ever, because they can cause objects on the screen to appear too small, resulting in eyestrain and squinting. Compare the two screens shown in Figure 3A.16. Both were taken from the same 17-inch monitor. The first image is displayed at 640\times480 resolution, the second image shows the same screen at 1280\times1024.

Monitors Refresh Rate A monitor's refresh rate is the number of times per second that the electron guns scan every pixel on the screen. Refresh rate is important be- cause phosphor dots fade quickly after the electron gun charges them with electrons. If the screen is not refreshed often enough, it appears to flicker, and flicker is one of the main causes of eyestrain.  Refresh rate is measured in Hertz (Hz), or dots fade quickly after the electron gun charges them with electrons. If the screen is not refreshed often enough, it appears to flicker, and flicker is one of the main causes of eyestrain. Refresh rate is measured in Hertz (Hz), or in cycles per second. This means that if a monitor's refresh rate is 100 Hz, it refreshes its pixels 100 times every second. When purchasing a monitor, look for one with a refresh rate of 72 Hz or higher. The high refresh rate can help you avoid eyestrain. Note that some monitors have different refresh rates for different resolutions. Make sure the refresh rate is adequate for the resolution you will be using.

Monitors Dot Pitch The last critical specification of a color monitor is the dot perch, the distance between the like-colored phosphor dots of adjacent pixels. In other words, if you measure the distance between the red dots of two adjacent pixels, you are measuring the monitor's dot pitch. Dot pitch is measured as a fraction of a millimeter (mm), and dot pitches can range from 15 mm (very fine) to 40 mm or higher (coarse). As a general rule, the smaller the dot pitch, the finer and more detailed images will appear on the monitor. Most experts agree that, when shopping for a color monitor, you should look for a dot pitch no greater than 0.28 millimeter (28 mm). That number generally applies to 15-inch monitors. If you want a larger monitor, look for an even finer dot pitch, such as 22 mm or less.

Video Cards Monitors The quality of the images that a monitor can display is defined as much by the Video card (also called the video controller or the video adapter) as by the monitor itself. As shown in Figure 3A.19, the video controller is an intermediary device between the CPU and the monitor. It contains the video-dedicated memory and other circuitry necessary to send information to the monitor for display on the screen. In most computers, the video card is a separate device that is plugged into the motherboard. In many newer computers, the video circuitry is built directly into the mother- board, eliminating the need for a separate cards video signal that controls magnetic yoke travels the video controller monitor. In the early days of personal computing, PC screens dis played only text characters and usually only in one color These displays took little processing power because there were only 256 possible characters and 2,000 text positions there are 307,200 pixels to control.  If you run your monitor at 256 colors, each pixel requires one byte of information. Thus, the computer must send 307,200 bytes to the monitor for each screen. The screen changes constantly as you work-the screen is up- dated many times each second, whether anything on the screen actually changes or not If the user wants more colors or a higher resolution, the amount of data can be much higher. For example, for "high color" (24 bits, or 3 bytes, per pixel will render millions of colors) at a resolution of 1024 x 768, the computer must send 2.359.296 bytes to the monitor for each screen. The result of these processing demands is that video controllers have increased draws magically in power and importance. Today's video controllers feature their own built-in microprocessors, which frees the CPU from the burden of making the millions of calculations required for dis playing graphics. The speed of the video controller's chip determines the speed at which the monitor can be refreshed. Video controllers also feature their own built-in video. PAM, or VRAM (which is separate from the RAM that is connected to the CPU) VRAM is dual-ported, meaning that it can send a screen full of data to the monitor and at the same time receive the next screen full of data from the CPU. Today's most sophisticated video controllers, which are fine-tuned for multimedia, video, and 3-D graphics, may have as much as 256 MB or more of video RAM.

Ergonomics and Monitors As you saw in Chapter 2, a number of health-related issues have been associated with computer use. Just as too much keyboarding or improper typing technique can lead to hand or wrist injuries, too much time at a monitor can endanger your eyesight. Protecting your eyesight means choosing the right kind of monitor and using it correctly.

Eyestrain Eyestrain is one of the most frequently reported health problems associated with computers, but is also one of the most easily avoided. Eyestrain is basically fatigue of the eyes, caused by focusing on the same point for too long. When you look at the same object (such as a monitor) for too long, the eye's muscles become strained. Think of how your arms would feel if you held them straight out for several minutes. Your shoulders and upper arms would soon begin to ache and feel weak; eventually you would have to rest your arms, or at least change their position. The same kind of thing occurs in eyestrain. Experts say that eyestrain does not pose any long-term risks to eyesight, but it can lead to headaches. It also can reduce your productivity by making it harder to concentrate on your work. Luckily, you can take several steps to reduce eyestrain when using a computer: Choose a monitor that holds a steady image without flickering. The dot phi should be no greater than 28 mm a the refresh rate should be at least 72 Hz.. Position your monitor so it is 2-2% feet away from your eyes, so that the screen's center is a little below your eye level. Then tilt the screen's face upward about 10 degrees. This angle will enable you to view the monitor comfortably without bending your neck. If you have vision problems that require corrective lenses, however, ask your optometrist about the best way to position your monitor. Place your monitor where no light reflects off the screen. If you cannot avoid reflections, use an antiglare screen to reduce the reflections on the screen. Keep your screen clean. Avoid looking at the monitor for more than 30 minutes without taking a break. When taking a break from the monitor, focus on objects at several different distances. It is a good idea to simply close your eyes for a few minutes, to give them some rest. Do not let your eyes become dry. If dryness is a problem, ask your optometrist for advice. Flat Video Is Anything But You may find it hard to believe, but it wasn't too long ago that a full 50 percent of my usable desk space was monopolized by my PC's monitor. And it wasn't just me. Since the first days of the PC, computer users have turned to video displays to see their work. Unfortunately, video displays are large, and big ones are huge. A video display with a 21-inch diagonal view was commonly in a case that was about two feet square! You lose desk real estate pretty quickly with hardware like that, but video monitors had one undeniable advantage: They were the only game in town. If you needed to use a PC and see what you were doing-always helpful- there was no alternative but to place what amounted to an overpriced television set smack in the middle of your work- space.  (In fact, early models of Apple brand personal com- puters actually did use television sets as their displays.) Early relocatable PCs weighed in at about 25 pounds, so the success of portable computing relied entirely on the success of making components lighter and smaller. Video displays were quickly replaced with a variety of panel-type screens. Batteries weigh more than most anything else, but small batteries were drained powerless in as little as 30 minutes by early flat panels. Flat panel screens are also delicate to manufacture, and yields-the number of usable products a factory makes (as opposed to the total number of a product that it tries to make that aren't useable for whatever rea- son)-were originally very low. This kept costs very high, which suppressed demand, which dismount in cheaper methods, and on and on. courage invest. It was around this time that the first freestanding flat panel displays for desktop PCs were marketed. For a variety of reasons-they were generally larger than notebook flat panel displays, and so were more expensive and difficult to manufacture, and they required a different type of video interface than was standard on every desktop PC at the time-desktop flat panels were priced well out of the reach of the average user. It was not at all uncommon for a desk- top flat panel to retail for twice what the entire desktop PC cost. They were, however, sharp and colorful and produced clear, vibrant images. Desktop flat panels definitely possessed the marketing "Wow!" factor (and they gave you your desk back). Demand increased and production technology improved. Slowly, prices began to fall. Now, roughly half way through the first decade of the twenty-first century, flat panels are everywhere. They re- main a bit more expensive than comparably-sized CRT video monitors, but that gap continues to shrink, and the so- called average PC system usually now includes a flat panel instead of a CRT.  As flat-panel displays for television and home theatre increase in popularity, technology will continue to improve and prices will continue to drop. Already, what was once a $2,000 desktop flat panel now costs less than one-third of that. But flat panels are in no danger of becoming boring technology. Already, people are transitioning from CRT- based home televisions to flat-panel screens.  A number of technologies are sparring for preeminence, and it's likely that several types of flat panel will continue to co-exist to meet the tastes and price-points of the world market. One of the newest developments in the flat-panel world might even herald the most significant change in home entertainment since the introduction of color television. Sharp Corporation recently introduced the world's first notebook computer with a true 3D display.  (By "true 3D" I mean a display that shows images in three dimensions without special glasses.) An innovative way of producing the flat panel itself (a matter of parallax, if you're curious) makes it possible for Sharp to send a slightly different image to a user's left eye than to his or her right eye. When the brain com- bines the images, it's tricked into perceiving depth. What this technology could mean for medical diagnostics, for pharmaceutical and genetic research, and for education is staggering.  What it could mean for entertainment-think "3D TV"-is astounding. For years, researchers have tried to develop practical three-dimensional television, most of which was based on dubious holographic processes or required cumbersome wired goggles or glasses. Displaying 3D content on this new screen simply requires the user press a button labeled "3D."  Already, at least one producer of the very successful IMAX3D movies has released their films on DVD, A number of major game manufacturers, including the ubiquitous Electronic Arts, also have agreed to develop 3D games for this new way of seeing. Sharp itself has created a 3D slide creator/ viewer that allows any user to create 3D images of family, friends, and places with an existing digital camera. Of course, there is no guarantee that any particular in- novation or technology will be the one that gets adopted universally and changes major aspects of our lives. There's also no publicly available evidence at the time of this writing that this system will work on the "living room" scale, as a three-dimensional entertainment system for whole families.  But Sharp has the distinction of having the first three- dimensional video system that is practical, convenient, and affordable. We may all need to come up with a replacement name for "flat panels." That old name just may not seem appropriate for long.

Electromagnetic Fields Monitors Electromagnetic fields (EMFs) are created during the generation, transmission, and use of low-frequency electrical power. These fields exist near power lines, electrical appliances, and any piece of equipment that has an electric motor. A debate has continued for years whether EMFs can be linked to cancer. Conclusions vary depending on the study and criteria used, but many people remain convinced that EMFs pose a health threat of some kind. EMFs have an electrical component and a magnetic component. Of the two, the magnetic fields raise the health concern because they can penetrate many kinds of materials. These fields, how- ever, lose strength rapidly with distance. To reduce your exposure to EMFs, take the following steps: Take frequent breaks away from the computer. Sit at arm's length away from the system unit, monitor, and other equip mend If possible, use a flat-panel display, which does not radiate EMFs

Data Projectors Monitors Portable computers have all but replaced old-fashioned slide projectors and over- head projectors as the source of presentations. Instead of using 35-millimeter photographic slides or 8.5- by 11-inch overhead transparencies, more and more people are using software to create colorful slide shows and animated presentations. These images can be shown directly from the computer's disk and displayed on the PC's screen or projected on a wall or large screen. To get these presentations onto the "big screen," data projectors are becoming increasingly common. (Data projectors also are called digital light projectors and video projectors.) A data projector plugs into one of the computer's ports and then projects the video output onto an external surface.  These small devices weigh only a few pounds and can display over 16 million colors at high resolution. Many projectors can work in either still-video (slide) mode or full-video (animation) mode, and can display output from a VCR or DVD drive as well as from a computer disk. Most projectors use LCD technology to create images. (For this reason, these devices are sometimes called LCD projectors.) Like traditional light projectors, LCD projectors require the room to be darkened. They display blurry images in less-than-optimal lighting conditions. Newer models use digital light processing DLP technology to project brighter, crisper images. DLP devices use a special microchip called a digital micromirror device, which actually uses mirrors to control the image display. Unlike LCD- based projectors, DLP units can display clear images in normal lighting conditions

Sound Systems Monitors Microphones are now important input devices, and speakers and their associated technologies are key output system. Today, nearly any new multimedia-capable PC includes a complete sound system, with a microphone, speakers, a sound card, and a CD-ROM or DVD drive. Sound systems a especially useful to people who use their computer to create or use multimedia pro ducts, watch videos or listen to music, or participate in online activities such as videoconferences or distance learning. The speakers attached to these systems are similar to those you connect to a stereo. The only difference is that they are usually smaller and may contain their own amplifiers. Otherwise, they do the same thing any speaker does: They transfer a constantly changing electric current to a magnet, which pushes the speaker cone back and forth. The moving speaker cone creates pressure vibrations in the air-in other words, sound.

Sound Cards Monitors The most complicated part of a computer's sound system is the sound card A computer's wind is a circuit board that converts sound from analog to digital form, and vice versa, for recording or playback. A sound card has both input and output functions.  If you want to use your computer's microphone to record your voice, for instance, you connect the microphone to the sound card's input jack. Other audio input devices connect to the sound card as well, such as the computer's CD ROM or DVD drive. You may be able to attach other kinds of audio devices to your sound card, such as tape players, record players, and others. As you learned in Chapter 2, the sound card accepts sound input (from a microphone or other device) in the form of analog sound waves. You can think of analog signals as fluctuations in the intensity of an electrical current.  The sound card measures those signals and converts them into a digital format, which the computer can use. To play back audio, the sound card reverses the process. That is, it translates digital sounds into the electric current that is sent to the speakers, which are connected to the card's output jacks. With the appropriate software, you can do much more than simply record and play back digitized sound. Sound editing programs provide a miniature sound studio, allowing you to view the sound wave and edit it. In the editing, you can cut bits of sound, copy them, and amplify the parts you want to hear more loudly, cut out static, and create many exotic audio effects.

Headphones and Headsets Monitors Many computer users prefer listening to audio through headphones or a headset, rather than using speakers. These devices are helpful when using portable computers, which do not have very high-quality speakers, or when playing audio might disturb other people. Headphones include a pair of speakers, which are attached to an adjust- able strap that can be custom-fitted to the wearer's head. Today, even inexpensive headphones (such as those that come with portable CD players) have reasonably high- quality speakers, are lightweight, and are comfortable to wear.  Nearly any set of standard headphones can be plugged into the output jack of a computer's sound card, as long as they have a "mini" stereo plug. For head- phones equipped with larger plugs, adapters are available.  A headset includes one or two speakers and a microphone, all mounted to an adjustable head strap.  The headset's microphone plugs into the sound card's microphone input, and the speakers connect to the sound card's speaker jack Headsets replace both remote microphones and speakers and are useful for speech-recognition applications, or when using the computer to make phone calls or participate in video confer phones.

Call of Wild Bioacoustics' Research Using high-tech hardware and software to "bug" the Earth's wild places from the African savannah to the ocean floor, scientists are gaining a better understanding of the secret lives of animals.  Bioacoustics Research gives scientists and researchers new insight into animal biodiversity by recording animal vocalization. This valuable statistical information yields a wealth of data about the health and behavior of indigenous animal populations. Those listening to the calls of the wild hear sounds ranging from clicks and rumbles to squawks and whines, as they try to interpret and analyze the sounds the creatures they study make. These Bioacoustics Researchers use sound to understand everything from the spawning habits of fish to the migratory path of herons to the social behaviors of humpback whales. The Bioacoustics Research Program (BRP) at Cornell University is one of the world's leading Bioacoustics pro rams. The computer software, techniques, and equipment developed at BRP for recording and analyzing sounds are used by scientists both at Cornell and around the world to study animal communication. One of the key tools used by the Cornell team is an ARU-an autonomous acoustic recording device-which consists of a microphone (or hydrophone), amplifier, frequency filter, programmable computer, and specially developed software that schedules, records, and stores the acoustic data.  The crucial features of the ARU are its small size, low power consumption, and large storage capacity (an ARU can collect up to 60 gigabytes of digital recordings). One exciting application of the technology is the ongoing study of whale communication. BRP has several projects underway recording ocean sounds in locations ranging from Southern California to the North Atlantic to the southern ocean. Subjects include the study of Blue, Finback, Bow- head, Minka, Humpback, and the highly endangered North Atlantic Right whale. For the collection of whale sounds, researchers use a special ARU device, called a "pop-up," for undersea deployment.  The pop-up is carried out to sea by ship or small boat and released, sinking to the ocean floor, where it hovers like a balloon tied to a brick. It contains a computer microprocessor, enough hard disks for up to six months of data. storage, acoustic communications circuitry, and batteries, all sealed in a single 17-inch glass sphere. An external hydrophone is connected to the internal electronics through a waterproof connector.  At the conclusion of a mission, the sphere separates itself from its anchor and "pops up" to the surface where it is recovered. Scientists then extract the data and process it to quantify ocean noises, detect endangered species, and describe the densities and distributions of different whale species. Back on land, the computer workstation used by Cornell is powered by RAVEN, a software application for the digital acquisition, visualization, measurement, manipulation, and analysis of sound. RAVEN was developed by BRP with sup- port from the National Science Foundation to provide a low- cost, user-friendly research and teaching environment tailored to the needs of biologists working with acoustic signals. Together, this combination of technologies have given scientists some of "the best profiles of any endangered species yet," according to BRP.

Summary  Computer monitors are roughly divided into two categories: CRT and flat-panel displays. Monitors also can be categorized by the number of colors they display. Monitors are usually monochrome, grayscale, or color. A CRT monitor uses an electron gun that systematically aims a beam of electrons at every pixel on the screen. Most LCD displays are either active matrix or passive matrix. >> When purchasing a monitor, you should consider its size, resolution, refresh rate, and dot pitch. The video controller is an interface between the monitor and the CPU. The video controller determines many aspects of a monitor's performance; for example, the video controller lets you select a resolution or set the number of colors to dis play. The video controller contains its own on-board processor and memory, called video RAM. A digital light projector is a portable light projector that connects to a PC. This type of projector is rapidly replacing traditional slide projectors and overhead projectors as a means for displaying presentations. Many digital light projectors provide the same resolutions and color levels as high-quality monitors, but they project the image on a large screen. The newest projectors use digital light processing to project bright, crisp images. A DLP projector uses a special microchip that contains tiny mirrors to produce images. Multimedia PCs generally come with sound systems, which include a sound card and speakers. The sound card translates digital signals into analog signals that drive the speakers. Many people prefer to listen to audio output through headphones or a headset, instead of using speakers.

Review Questions : 1. There are two basic types of monitors used with PCs. List them. 2. How does a color CRT monitor produce images on the screen? 3. What are two disadvantages of CRT monitors, compared to flat-panel displays? 4. What are two disadvantages of LCD monitors, compared to CRT monitors? 5. How does a plasma display monitor work? 6. List the four factors you should consider when comparing monitors. 7. As it relates to monitors, what does the term "resolution" refer to? 8. What is dot pitch? 9. How should you position your monitor, if you want to avoid eyestrain? 10. How does digital light processing (DLP) technology work? 11. How are monitors categorized based on the color features? 12. What is a pixel? Explain. 13. What is LCD? Expand and explain. 14. Explain the term "submarining". 15. What is VRAM?