Computer Monitors
The computer monitor is an output device that is part of your computer's display system. A cable connects the monitor to a video adapter (video card) that is installed in an expansion slot on your computer’s motherboard. This system converts signals into text and pictures and displays them on a TV-like screen (the monitor).The computer sends a signal to the video adapter, telling it what character, image or graphic to display. The video adapter converts that signal to a set of instructions that tell the display device (monitor) how to draw the image on the screen.
Cathode Ray Tube (CRT)
The CRT, or Cathode Ray Tube, is the "picture tube" of your monitor. Although it is a large vacuum tube, it's shaped more like a bottle. The tube tapers near the back where there's a negatively charged cathode, or "electron gun". The electron gun shoots electrons at the back of the positvely charged screen, which is coated with a phosphorous chemical. This excites the phosphors causing them to glow as individual dots called pixels (picture elements). The image you see on the monitor's screen is made up of thousands of tiny dots (pixels). If you've ever seen a child's LiteBrite toy, then you have a good idea of the concept. The distance between the pixels has a lot to do with the quality of the image. If the distance between pixels on a monitor screen is too great, the picture will appear "fuzzy", or grainy. The closer together the pixels are, the sharper the image on screen. The distance between pixels on a computer monitor screen is called its dot pitch and is measured in millimeters. (see sidebar). You should try to get a monitor with a dot pitch of .28 mm or less.
Note: From an environmental point of view, the monitor is the most difficult computer peripheral to dispose of because of the lead it contains.
There are a couple of electromagnets (yokes) around the collar of the tube that actually bend the beam of electrons. The beam scans (is bent) across the monitor from left to right and top to bottom to create, or draw the image, line by line. The number of times in one second that the electron gun redraws the entire image is called the refresh rate and is measured in Hertz (Hz).
If the scanning beam hits each and every line of pixels, in succession, on each pass, then the monitor is known as a non-interlaced monitor. A non-interlaced monitor is preferred over an interlaced monitor. The electron beam on an interlaced monitor scans the odd numbered lines on one pass, then scans the even lines on the second pass. This results in an almost imperceivable flicker that can cause eye-strain.
Interlaced computer monitors are getting harder to find (good!), but they are still out there, so keep that in mind when purchasing a monitor and watch out for that "steal of a deal".
Keyboards
A computer's main input device is the keyboard, and it's almost impossible to imagine a computer without one. A computer keyboard looks alot like the keyboard for a typewriter but has added keys that provide many different features and enhancements. The keyboards sold today are called enhanced keyboards and have 101 to 106 individual keys. The layouts are basically the same with the odd key situated differently. They generally hook up to your computer with a DIN-5, PS2 (mini DIN-6), or USB connector.
Keyboards can definitely have a certain feel or touch to them and it's best to try one out before you buy. Some can be quite springy while others feel kind of mushy, others have a definite snap or click to them. Some actually make a clicking sound as you type (some people might like this, it drives me nuts). There are split keyboards and ergonomic keyboards meant to help reduce the possiblity of carpal tunnel syndrome.
Of course, you get a keyboard when you buy a computer, but it's not an overly expensive item and can easily be replaced with one more to your liking. When I say it's not an overly expensive item, I'm referring to the generic keyboards sold with the average computer system. The newer high-tech, exotic colored, ergonomic, split keyboards sporting extra buttons for the CD player and instant internet access with page-scroll and touchpad are starting to get up there in price.
Once you've found a keyboard that you find comfortable, one of your main concerns should be proper typing form. Repetative stress injuries are a concern and poor posture can also result in back and neck pain. Sit up straight and find yourself a chair that supports the natural curve in your back. It should be adjusted to your keyboard so that you don't have to lean forward or hunch to type. Your shoulders should be relaxed with your forearms and wrists fairly level, fingers slightly curved. Wrist pads are made for you to rest your wrists on while taking short breaks, your wrists shouldn't be on them while you type. Don't sit and type constantly, try to take a few breaks every now and then and have a stretch.
Troubleshooting
Keyboards are fairly trouble-free input devices. However, sometimes troubles do arise and there are a few relatively simple fixes.
No Response
If you can't seem to get any response from your keyboard, the first thing to check is the connection. Make sure the connector is plugged securely into the proper port. Sometimes it's possible to plug into the wrong port if both your keyboard and your mouse use a PS2 connector. Unless it attaches with a USB connector, make sure your computer is off before you plug or unplug your keyboard or mouse. If your keyboard is unplugged when you boot your computer, you'll get a 'keyboard error' that may or may not halt your system, depending on your computer's setup. Another thing that can cause this error is if there's a key stuck down or if something is resting on a key during bootup.
One more thing on this particular subject, computer cases used to have a keylock switch on them. They're not found on cases that often now, but some do still have them, especially network servers. This allows a person to lock out keyboard access to any unwanted users. This might be something else to check if you're not getting any response from your keyboard.
Sticking Keys
If you have a key or several keys that stick after being pressed, it may be a little difficult to pinpoint at first, but you'll probably soon figure it out. Have you maybe spilled coffee or coke on your keyboard recently? Do you eat over it, smoke a pipe or cigarettes at your computer? It is possible to rinse a keyboard with water, let it dry thoroughly, and use it again. If it's just a couple of keys, you can pop the caps off with a chip puller and try to clean underneath. Be careful of the longer keycaps like the Enter key, Shift keys, and spacebar, they have small metal hangers under them to keep them level when pressed. It's really easy to break these if you don't know how to get them off properly. Yes, it is possible to take all the keycaps off, take the keyboard apart and wash everything down, but consider what your time is worth too. By the time you've removed all the keys, washed everything, dried it properly, and replaced the caps, a new keyboard might have been a more economical answer. Then again, if you're going to replace it anyway, why not just try rinsing it under the sink or putting it through the rinse cycle in the dishwasher without any soap. After allowing it to dry thoroughly, test it out. If it works, great, if not, buy a new one.
Change the Settings
If you find your keyboard doing strange things, check out the Control Panel. If someone else uses your computer, maybe they've toyed with the Keyboard Settings or set some of the Accessability Options. If text is being overwritten instead of inserted when you type, check the Insert key, this toggles between insert and overwrite.
Although not all that common, keyboards can also have electrical shorts and wiring problems. It's nice to have a spare keyboard that you can swap in and out to eliminate the possibility.
Care and Cleaning
Keyboards can be cleaned with mild soap and water on a damp cloth that's been well wrung out. Turn your keyboard upside down and tap it on the bottom to knock out crumbs and ashes or food particles, then use canned air to blow the dust, grime and dead skin out from under the keys. I don't suggest using Isopropal Alcohol, but if you choose that route, try it on a small, unnoticable spot first to make sure it doesn't melt or smear the plastic finish. Keeping your keyboard covered when not in use can help keep out the dust. If your fingers are particularly grimy then you can buy keyboard 'skins' that fit over the keys to keep them clean and prevent dust, dead skin and other particles from getting underneath.
The Mouse
The mouse is a device that translates movements on a horizontal surface into movements of a pointer on the computer screen. While the keyboard is, by far, the most important input device attached to your computer, the mouse runs a close second, and may be the most used.
The mouse's popularity is due, of course, to the popularity of the graphical user interface (GUI). The first mouse was developed in the mid '60s. Looking back at the early computer interfaces, and even the physical number of computers in the '60s and '70s (or lack of numbers), it's obvious that the mouse was an animal before its time. When IBM's Personal Computers hit the market in the early '80s, with the DOS command line interface, more and more people found it possible to have a computer in their home. With the introduction of menu-driven programs, the mouse began to see limited use. When the Mac GUI OS was introduced, the mouse was recognized as a valuable tool by Macintosh users, but when Microsoft mass-marketed its Windows Operating system, the mouse truly became a household word.
I've got to admit, when I first saw a GUI (Graphical User Interface), I wasn't all that impressed. I thought it seemed a little mickey-mouse-like and made the computer look more like a toy than the high-tech, effective tool that I knew it to be. When I look back at it now, I think it was more the fact that I might have felt a little cheated. It took so much time and energy to master the computer, and now it appeared as though everyone was going to be able to use a device that, up to that point, had been the semi-private realm of the techie, DOS savvy minority. And actually, that's exactly what happened. The GUI and the mouse are probably the two most important factors leading to the household personal computer being second in popularity only to the television set. (Not to mention constantly improving, lightning fast technological advancements and intelligent, aggressive push-marketing.)
Types of Mice
There are basically three different types of mice: mechanical, optomechanical and optical.
The mechanical mouse has a small hard rubber ball underneath that moves against two rollers as it's passed across a flat surface. Mechanical sensors detect the movement of the rollers as an 'x' and 'y' axis and the cursor on screen is moved accordingly.
An optomechanical mouse works on the same principal. The rollers have wheels on the end of them with evenly spaced holes. As the wheels spin, a light-sensitive optical device counts the number of holes that pass by and convert those numbers to an 'x' and 'y' axis.
An optical mouse is more accurate or precise and has no moving parts. It uses a laser to detect movement and has to be paired with a special pad or mat that has an embedded optical reference grid.
Mouse Connections
The serial mouse is, by far, the most popular and the easiest to install. They connect to an RS-232C serial port; one of the COM ports on the back of the computer (a DB-9 or a DB-25 male connector). A serial port is an interface that transmits one bit at a time, and RS-232C is a standard that most serial ports conform to. The fact that they do take up a COM port (and it's respective IRQ) is the biggest problem with the serial mouse. Personal Computers are very limited to the number of COM ports available.
The bus mouse was originally developed to help alleviate the problem of the COM port shortage. It connects to the computer through a small round connector (female mini-DIN-9) on the back of an expansion card installed on the motherboard. Because an expansion card had to be configured and installed on the motherboard, these mice were considered much more difficult to install. Now they are pretty well obsolete. They did free up a COM port, but they still took up an IRQ as well as an expansion slot.
The PS/2 mouse seems to be the answer to both problems. It's a type of serial mouse but it connects to a PS/2 connector (female mini-DIN-6) that is hard-wired directly to IRQ 12. It installs as simply as any serial mouse, doesn't use up a COM port, and needs no expansion card installed. Not only that, but it uses a fairly obscure IRQ that was mostly unavailable to other devices.
A cordless mouse uses infrared technology to do away with the cord. It seems like it would be a good idea because the cord on a mouse can be a real pain. It drags across the top of the desk, gets caught and hangs up in the other cords, or anything that might be lying on your desktop. They also have a receptor that must be visible to the mouse (line of sight), if anything is in the way, the mouse won't respond. This can sometimes cause a little aggrivation unless you keep a very tidy desk. Cordless mice are more expensive than other types.
The USB mouse is, by far, my favorite. With Windows98, USB has become one of the most advanced (and one of the best) connections around for mice, printers and other peripherals. Installation is simple. It's hot-swappable, so you can plug it in even when your computer is running. The mouse is immediately recognized and you can use it right away.
Care & Maintenance
The most used and abused cord on your computer is the mouse cord. It's dragged, pulled, yanked and twisted everyday with normal use. Try to provide the cord free movement as much as possible and allow a little slack at all times.
The mousepad itself can make a difference in the amount of gunk that builds up on the inside rollers. The pad with the porous cloth surface will hold all kinds of dust, grime, dead skin and moisture that tends to transfer to the rollers via the rubber ball. Get a pad that has a harder, plastic type surface. It won't get loaded up with as much crap and it's a lot easier to clean, just wipe it with a damp cloth.
If your mouse cursor seems to jump or jerk across the screen, or actually stops as though its hit a wall and doesn't seem to want to move properly, it's probably dirty. This is caused by the buildup of gunk on the rollers that was mentioned earlier. The word gunk is a highly technical computer term that refers to the grime, dust, dead skin and debris that transfers onto the mouse rollers and can build up to the point where it touches the plastic edge of the mouse and actually stops the roller from turning. This is what makes the cursor on your screen stop dead in its tracks. While this can be very frustrating, it's an easy problem to solve. To clean these rollers:
Close out of Windows and shut the computer off. Disconnect the mouse and turn it upside down. You'll notice a faceplate around the ball. Remove the faceplate. It may twist a quarter turn or it may click forward (usually, there's arrows to indicate). Carefully turn it over and remove the ball. Don't try to see if the ball bounces! When it hits the floor, it will put it out of round and ruin it. And in case you're still wondering, they don't bounce too well at all. You can clean the ball with luke warm water and a lint free cloth. Don't use alcohol or cleaners on it. If you look inside the cavity left by the ball, you'll see the rollers. You'll also be able to see any buildup (gunk) on the rollers. Dab the buildup with a little isopropol alcohol and then gently remove the buildup with a toothpick or a small flathead screwdriver. Be careful not to scratch the rollers. When everything is completely dry, you can reassemble the mouse, plug it in and turn on your computer. There'll be a noticeable improvement.Ports & Connectors
The various connectors and ports on the computer allow it to communicate with the many different devices and peripherals attached. Because there are so many cables and cords attached to the back of the computer, and so many different types of connectors, it often seems a little intimidating to the newer user. Although there are some devices which may use the same connector or port, the individual devices and their cords can only physically attach to one certain type of connector; so don't feel nervous about hooking your system together.
There's really no way you can do any harm to your computer just by hooking it up, as long as you follow a few common sense rules:
The first thing to know is the difference between a male and female connector. The male connector fits inside the female connector. If the connector has pins protruding from it, its a male connector. If the connector has holes for the pins to fit into, then its a female connector. When you hook something up to your computer, the male and female connectors are hooked together. The connectors on the back of your computer are called input/output ports (i/o ports) or communication ports.
The second thing you should remember is that when you join a connector to a port, they must have the same shape and the same number of pins or holes. In other words, a square peg won't fit into a round hole, and its not wise to try to jam fifteen pins into nine holes (part of the 'common sense' thing I was talking about).Which brings us to another very important point, never force anything.
Here's one that's hard to do. Always make sure the computer is off before attaching connectors or cables to any of the ports. This can cause little power gliches (another technical word) that could corrupt an open file or cause a program to freeze. It can even cause a small short that could damage or ruin components inside your computer. I know, you've done it a hundred times and never had a problem. Well, that's good. If you want to continue to practice risk management, that's your perogitive, but be aware of the possibilities and don't be surprised when you finally get burned. USB ports are the only ports that should be considered hot-swappable (this means they can be plugged in or unplugged while the machine is on).
Only one more thing to remember. There are small hexagonal nuts on either side of many of the ports on your computer. These allow you to screw the connectors in so they don't accidentally fall out or loosen. They just have to be screwed down, they do not have to be tightened. These nuts are actually the heads of small bolts that pass through the back plate on your computer and are attached with a small nut on the other side. If you tighten the screws too much, then when they're undone, they may take the bolt with them and the small nut may fall off inside the computer (onto the motherboard or an expansion card). Not a good thing.
Now that we know the basic rules, let's take a look at some of the connectors or ports you might find on your computer.
DB Connector
The most common connector is the DB connector. It's sort of a 'D' shape and is sometimes called a D-shell connector (go figure). It's designated as DB-x, with 'x' being the number of pins or holes on the individual connector. So a DB-9 female connector would be a 'D' shaped connector with 9 holes. This would receive a cord with a DB-9 male connector (with 9 pins).
If you find a DB male connector port on the back of your computer, (either a DB-9 male or a DB-25 male) it's going to be a serial port. Serial ports are also called COM ports or RS-232 ports (Reference Standard #232 as referenced by IEEE*). Serial ports transmit data one bit at a time and are relatively slow compared to other ports. However, they are plenty fast enough for some external devices such as a mouse, or an external modem. Because only one bit at a time is passed along a serial cable, it can travel a fair distance before data integrity is challenged (or errors start to occur). A serial cable shouldn't be more than 50 feet in length.
Incidentally, in case you were wondering, if you have a device with only nine holes on its connector, and only a DB-25 male serial port to connect to, all you need is a 9 to 25 pin adapter. There's no difference between a 25-pin serial port and a 9-pin serial port other than the fact that the DB-25 male has sixteen extra pins that it doesn't use.
If you have an older computer, and see a DB-9 female connector on the back, it's probably a video connector for an older EGA or CGA monitor. My guess is that you won't see one on your computer. However, if the question should ever come up, it could also be a Token Ring network adapter port.
Look on the back of your computer, you may be able to find two different DB-15 female connectors. If you see three rows of five holes, then it's your VGA or SVGA video monitor adapter. If you see only two rows (one of eight holes and one of seven), then it's probably a joystick adapter.
A DB-25 female connector on the back of your computer is going to be a parallel port. Parallel ports can transmit data eight bits at a time which creates a noticeable speed increase over serial ports. Most commonly used as printer connections, several other devices now use the parallel port such as tape backup systems, Zip drives and scanners to name a few. These devices are generally fitted with what is referred to as a pass-through port. This means that you can hook up your scanner to the parallel port (DB-25 female) and then connect your printer to the DB-25 connector on the back of the scanner and have access to both devices. This usually works well but does pose some problems. First off, the device has to be turned on for the pass-through port to work. To take this one step further, the device often has to be turned on before the computer is booted, to be recognized properly and for the right drivers to be loaded at startup. Also, users tend to think that they can daisy-chain these devices. In other words, connect their scanner to the computer, attach their Zip drive to the back of the scanner, their tape drive to the back of the Zip drive, and then their printer to the pass-through port on the back of the tape drive. Believe it or not, I've seen this done and I've seen it work (more or less). I've also seen it work one day and not the next. It's a hit and miss sort of thing (more miss than hit) and I wouldn't trust the integrity of the data past the second device.
Another thing to keep in mind, is that the cable on a parallel device shouldn't be more than 10 feet long. Data errors can occur beyond this distance.
DIN Connector
The DIN connector is a small round connector, usually with a keyed slot for proper orientation. Again, it's designated as DIN-x, with 'x' representing the number of holes or pins on the connector. It comes in a couple of different sizes and it's been used on computers about as long as the DB connector has. It's a fairly popular connector because of its small size and solid connection.
The most common DIN connector would have to be the DIN-5 keyboard connector. Its the largest of the DIN connectors that you're going to find on your computer and its been around for a long time. If you own a newer computer, then the DIN-5 has probably been replaced with a DIN-6 (mini-DIN or PS/2) connector.
The PS/2, or DIN-6 connector, was mainly used by Macintosh computers for the longest time (Macintosh also used a DIN-8 connector for their printer). You may hear them referred to as a mini DIN-6 connector. They're smaller and more compact than the typical DIN-5 connector and have become the standard for both the keyboard and the mouse on newer PCs. If this is the case on your computer, then the two DIN-6 female ports on the back of your computer are going to look an awful lot alike, and you need to distinguish between the mouse port and the keyboard port before hooking them up. They may be color coded or they may have a little icon beside them representing their use. Whatever the case, you're not going to do any harm if you accidentally get these two devices switched. Your mouse won't work, or you'll get a keyboard error at boot up. Your first course of action for troubleshooting this type of problem should be to check the connection anyway.
Another port you could find on the back of an older computer is the DIN-9. It would be another mini DIN port with 9 sockets. A bus mouse or a hand-held scanner may use this type of port, but it's unlikely that you're going to find one on a newer computer.
RJ Connectors
The RJ connector is used for communication devices. If you live in North America and have a jack on your wall that your phone connects to, that's an RJ-11 connector. Now, the RJ-11 connector or port doesn't have 11 pins or 11 holes. As a matter of fact, it only connects 4 or 6 wires.
You may have an RJ-11 connector on the back of your computer if you have an internal modem. This is to hook a phone line up allowing communication with other computers and access to the Internet and the World Wide Web.
If you see two RJ-11 connectors side by side, it means that you can hook the phone line to your computer using the one jack, and then an extension phone can be plugged into the other jack. A lot of modems today allow for fax and voice capabilities. This means that you can fax from your computer, it can double as an answering machine that records messages and voice mail, and, if you have speakers and a microphone, you can even use it as a speakerphone.
An RJ-45 connector looks much like the RJ-11, only larger. It connects 8 wires and is used for network ethernet connections. If you see and RJ-45 connector or port on the back of your computer then there's two
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