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Input / Output & Peripherals
For starters, input/output is the computers equivalent to our sight, hearing, speech, etc., simple enough. But computers are not as sophisticated as humans and the input/output processes of computers are a lot more pedestrian. Strictly speaking, most devices listed on this page do not really belong into the frame of 'Build your own PC', but since there is more to building a modern computer than putting it's intestines together, I am listing some brief information about popular input/output peripherals as well.
There is not much to say about keyboards. The most important thing to watch out for is the connector. If you build an ATX system, you'll need a keyboard with a PS/2 connector, if you build an AT system, you'll need one with a DIN connector. Or you can get yourself an adapter. Most new keyboards you come across these days have a nice non-click touch and feel and are as ergonomic as possible, hence eliminating the need for a wrist pad. You can still get click keyboards though if you prefer to "hear" your own stokes, but I would not recommend them, they will only drive you crazy. The difference between click and non-click keyboards is their design. Click keyboards are mechanical, whereas non-click keyboards use soft rubber membranes to close contact. If you like ergonomic designs, have a lookout for a genuine economic keyboard, but the fully ergonomic shape is difficult to get used to and unless you can touch-type you will only get confused. I always prefer a straight one. There are also a lot of keyboards out there with fancy programmable buttons and add-ons. At the end of the day it really depends on your own personal taste. If you go for the plain and simple type, make sure you don't pay more than £10.00 or £15.00. Depending on the market and where you buy, you can get them even cheaper than that.
Pointers, such as mice, trackballs or touch pads, come in all sorts of different shapes and designs. As with keyboards, on of the most important things to look out for is the type of connector. ATX systems and almost all newer ATs want a PS/2 connector, anything older, up to the actual IBM PS/2, needs a serial type connector. If you have the choice, always go for PS/2, especially if you've got an internal modem. Modems are serial devices, and an internal modem might request the same interrupt than your mouse, hence causing a conflict, which, in best case, slows down your connection. A standard mouse uses a ball inside the housing at the bottom to represent movement. Two rollers rest against the surface of the ball, one for the X axis and one for the Y axis. The X axis detects the movements for left and right, the Y axis the movement for up and down. As the ball moves, the rollers for each axis rotate turning a wheel that is attached to the end of each roller. As the wheel turns according to the movement of the mouse, an LED (Light Emitting Diode) shines at a pair of photo transistors at the other side of the wheel. Because the wheel has small slots in it, the light appears to blink as it shines through the slots. The photo transistors use this 'code' to read the turning of the wheel and convert it into binary code. Other types of mouse pointers use potentiometers and capacitors to detect the movement, but the opto-mechanical approach seems to be the most common one these days. In all cases the pointer is used to move the cursor around the screen. There are a variety of pointers on the market and it is entirely a matter of preference whether you decide to buy a conventional mouse a trackball, a touch pad or something completely out of this world. Just as long as you are happy with the device. Be aware of the impact a wrong design can have on your health though. The bigger the device, the more strained will be your wrist, so make sure your pointer fits the size of your hand and is easy to maneuver. Whichever supplier you favour for your decision, basically all mice work in the same way. You can get a standard mouse from as low as £5.00 or £10.00. One good tip is to go for a mouse with a wheel, such as the Microsoft IntelliMouse or the Genius NetMouse Pro. The wheel enables the user to quickly zoom in and out or scroll up and down a page in a browser in order to speed up operations. Well worth a consideration and only a little more expensive than conventional mice. Most pointer manufacturers have now adopted the middle wheel or scroll buttons as standard.
Computer speakers differ from conventional speakers only in two ways: they are normally self amplified and magnetically shielded. Depending on the power of your sound card it might be possible for you to get some half decent sound out of non-amplified speakers, but the "On" switch really makes all the difference. Most speakers can take standard AC power supplies and have separate volume and tone controls. Others come with a power connector that plugs into your PSU or monitor. Some monitors offer build in speakers - just like TVs, but if you want some real hi-fi power, chances are you are going to spend another £15.00 or £20.00 for a decent pair of speakers. If you have a sound card with quadraphonic capabilities you need to fork out over £50.00 for a decent four-point subwoofer sound system, the result, however, is really breathtaking. There are two main types of joysticks available:
Since joysticks are mostly used for game play, it really depends on the type of games that you are interested it. Digital joysticks behave rather like the keyboard would, in that the movement that is controlled is rather rapid than smooth. You go left, right, up and down bit by bit, where every bit of movement is as big (or small) as the other. Analogue joysticks behave rather differently in that they are essentially X/Y controllers, where every axis can be controlled variably. This makes analogue joysticks much smoother for games where fine control is important. The actual movement of the joystick is is controlled in much the same way that some mouse pointers use. The actual stick extends into a metal shaft with two metal yokes reading the movement of each axis for a 90 degrees angle, rather like a cross. The yokes have pivots at the end that allow them to swing freely back and forth. The metal shaft is also pivoted where it enters the base, and when you move the stick in your hand, the other end that sits in the housing moves in the opposite direction. As the shaft moves from end to end, the potentiometers at the end of each yoke take a precise reading of the movement and convert it into binary signals. Digital joysticks simply have switches, rather than yokes and potentiometers. You might remember potentiometers from the time you used to play with your electric train or racing track. Potentiometers are variable resistors and the amount of current that is let though is directed by the amount of movement that is detected. In a joystick, each potentiometer is connected to a capacitor. When the joystick is moved into one direction, the potentiometer turns and the resistance within the capacitor increases. When the joystick is moved into the other direction, the resistance within the capacitor decreases. When the resistance increases, the capacitor takes longer to discharge, and when the resistance decreases, the capacitor discharges faster. The time the capacitors need to discharge is measured by the PC, which uses the times between the successive discharges to determine the position of the joystick and so the degree and direction of its movement. Basic joysticks are available for the price of a standard mouse pointer, but if you're into heavy game play, you're want something like a force feedback joystick. I admit I am not into games that much, but I have always been very happy with my Gravis Game Pad. I prefer game pads to joysticks because they offer more controls and are much smaller, i.e. easier to handle.
Basically, digital cameras are not that much different than conventional cameras. Both expose light sensitive materials to light and both use the same exposing techniques. But whereas conventional cameras use light sensitive film for the exposure, digital cameras use CCD (Charge Coupled Device). Within the digital camera the CCD sits in the same place where the film is in conventional cameras, exposing thousands of light sensitive pixels to the light. Each pixel converts the received information (i.e. colour, intensity, etc.) into an analogue electrical signal which is converted into binary by the ADC (Analogue to Digital Converter). Very much in the same way that the DAC on your graphics card converts digital information into analogue. The resolution (i.e. quality) of the stored picture depends largely on the amount of pixels on the CCD. After the ADC has converted the analogue information into digital, the DSP (Digital Signal Processor) enhances the contrast and detail of the image and sends it to the camera's storage medium in compressed format. Storage usually takes place on CF (Compact Flash) cards, which are of the same type than the ones used in palmtops and handheld PCs. Depending on the capacity of the CF, the digital camera can store up to dozens of images which later can be uploaded to a computer for further processing or printing. Major factors to consider when buying a digital camera are:
If you are into photography, you will probably already own a photo editing suite like Paint Shop Pro or Adobe Photoshop. Which package you use in the end is not as important as you being able to make proper use of it. Most photo suites are capable of delivering quite astounding features and effects. I have been asked many, many times what I think of digital cameras, so here's my piece of advice for you: If you're a 'Polaroid' kind of person who needs pictures done quickly, of if you need your images in digital format (i.e. for the Web, multimedia presentations, etc.), then a digital camera is probably just what you want. They take good quality pictures and are not even expensive any more. Just as long as you are aware that, with digital cameras more than with anything else, you get what you pay for. So don't be too tight with your purse. If you're really into photography and want high quality output, there is still nothing better out there as the good old trusted Single Lens Reflex. Safe you money and get a good scanner instead, they are much cheaper and produce generally better digital input.
There is not that much to say about PC microphones. They are essentially exactly the same kind of microphones than any other you can buy. The recording quality depends more on the quality of your sound card than on the microphone itself. Depending whether you have a stronger or a weaker soundcard, you might need a microphone with a higher impedance. There are some microphones available that feature their own little amplifier, which is powered by a lithium battery. When making any kind of recording, make sure that the background noise of your environment (i.e. your living room) is as low as possible. Especially if you are making telephone calls over the Internet or are in a video/audio conference. Audio signals transmitted over the Internet are not as good by far than what you are used to from your telephone. I recommend you buy a microphone though. Internet phone calls are getting more and more common, and if, like me, you have relatives abroad, chatting away over the Internet will not stretch your purse anywhere near an international telephone call.
Unmistakably, scanners are input devices. Images are scanned in and can be processed by the computer, may it be in form of graphics or text documents which can be read directly into a word processor. The first flatbed scanners used complex mirror and lens arrangements, but improvements in technology have made scanner constructions a lot simpler and cheaper.
When you decide to buy a scanner, ease of use and the software features should play as much of a role as image quality. The expansion of the World Wide Web and desktop publishing have made the scanner more common, even indispensable. Today's mid range scanners put the high end scanner of yesterday to shame, and come in at very reasonable prices. Most scanners these days are flatbed devices, don't buy handheld scanners or printer add-ons, they are inferior in quality and comparatively expensive. All flatbed scanners are basically just a rectangular plastic box with glass on the top and a reading slider inside. The quality of a scanner depends on its maximum resolution and colour depth.
Colour Depth Colour depth is measured by how many layers of each of the three primary colours (red, green, blue) the scanner can read. It is exactly the same principle as monitors use to output colours. A 24 bit scanner, for example, will scan each of its primary colours at 8 bits, that is 256 levels. 256 levels of each colour equals 16.7 million combinations of colour. That's pretty accurate, and if a 24 bit scanner could actually attain 8 bits at each colour, they would produce extremely high quality images. The problem is that they only get about the first six bits of each colour exactly right. There is a lot of data to be recorded, and in the attempt to process it all, some data is lost, therefore the image quality, especially in the highlights, suffers. A 30 or 36 bit scanner records 10 or 12 bits per colour. If the last two don't come in so well, so what? That still leaves 8 to 10 bits per colour. 30 bit scanners are what the 24 bit scanners should be. In theory, the more bits, the better. However, image quality varies tremendously, so not all 36 bit scanners are equal in quality. These days even the cheapest of scanners offer 36 bit and, unless you really need 100% accuracy, they do just fine. Mine was £65.00 and it does exactly what it's supposed to do.
Resolution A scanner's resolution is generally reported in two planes. A 600x1200 dpi scanner collects 600 dpi (Dots Per Inch) on the horizontal plane and 1200 vertical. Although scanners actually only collect data at their optical resolution, the software can interpolate other resolutions, down to a few bits per pixel or up to tremendously fine detail. The software fills in the gaps and softens the jagged edges, providing a simulation of higher resolution. Today's budget scanners offer true scanning resolutions of about 1200x1200 dpi with software enhancements of 9600 dpi or higher.
Parallel or SCSI I have already mentioned the SCSI interface in the Hard Disk Drive section. SCSI scanners are generally scanning a lot faster and produce a higher true scanning resolution. The benefit of deciding for a scanner that simply plugs into the parallel port is its much lower price. Parallel scanners have a slower scanning speed and suffer from lower quality input. However, you will never be able to get the most out of a SCSI scanner unless you are producing professional reproductions. For all us mortals a parallel scanner will do the job as superbly as can be expected. If you decide for a parallel scanner, you can either plug your scanner straight into your PC and your printer into the scanner, or you can opt for a second parallel port. The choice is yours.
Scanning Tips Whatever the capabilities of your scanner are, the input that it can achieve will be a lot better than the best output quality of your printer. Generally, scanning at 300 dpi for printing is a good setting for most images and documents. Even for photographic reproductions, I would never scan at higher than 600 dpi. The best file format for those sort of scans is .jpg with 15 to 25 percent compression. If you are scanning documents in black and white only, don't scan at a higher than 200 dpi resolution. Everything above only wastes space. If you are scanning images for your Web Site (i.e. for the monitor to be output), scan at 72 to 100 dpi. The resolution of your monitor is only 72 dpi, so keep your images as small as possible in order for your pages to load fast. Text for OCR (Optical Character Recognition) will not scan well at low resolutions. Chances are, if you are scanning text for OCR, you will not keep the original scan anyway, so scan at least at 300 dpi. The more accurate your scans are, the more accurate the recognition will be.
There are lots of different printer types on the market, so I will probably extend on printers at a later time, or even give them a section of their own. But for now, here are just the basics. The Most commonly use types of printers in a domestic environment are:
Dot Matrix printers are still around, but are now really only used in commercial environments for invoice and report printing, where quality and speed are not important. As the name implies, inkjet printers use tiny dots of ink to generate the output. Before making a choice of what printer to go for, there are a variety of questions you should ask yourself. For starters, how important high quality output? Is the printer mend to be for your children to print their pictures, or do you intend to achieve near photographic output? These days all printers produce resolutions of at least 360x360 dpi as standard and that kind of resolution will normally do for any kind of domestic printout. For near photo realistic quality you need at least 720x720 dpi, so watch out for the highest possible resolution that the printer of your choice can produce. Speed is another factor to consider. If you need high speed and/or high volume prints, then you should not even consider an inkjet printer but opt for a laser jet. But even inkjets can be quite fast. Some achieve up to eight pages per minute in grayscale, some need 30 seconds for a single page. All inkjet printers need a lot longer to print once colour is involved but even there you have big speed differences. One of the most important things to consider is how many cartridges it holds. This is important for ease of use and for output quality alike. A printer that takes two cartridges (colour and black) will by default produce much better results of black prints. Inkjet printers that only take one cartridge at a time will either not be able to print in colour (when the black cartridge is inserted) or have to produce the colour black by heavily mixing its primary colours cyan, yellow and magenta. This will slow down the printing process and achieve less quality, these type of inkjets are cheaper to buy. Don't be mislead though, as the individual cartridges can be more expensive and they don't last as long, making the printer less economical in the long run. I recommend a printer that takes two cartridges. They're also easier to use and less troublesome. It is commonly known that ink cartridges can be refilled. If you intend to take up the challenge and get your hands dirty, make sure that the ink you buy matches the criteria of the ink that your printer uses. Most printers use water based ink, but Epson printers, for example, use spirit based ink in order to achieve higher quality output. I won't tell you how to refill your cartridges, you can read that up in the instructions that come with the refill pack, but I tell you that much: be careful with that syringe!
There is not much to say about Input/Output cards. Typically you shouldn't need to buy an I/O Card as your motherboard usually supports all necessary devices. However, if a device on your motherboard fails, you'll need to make this extra purchase. When talking I/O cards, always think of IDE cards. I/O cards have brought about the Integrated Drive Electronics standard in the first place, after which IDE became so popular that is was considered standard not long after. All Input/Output cards normally support:
Chances are you never need bother with an I/O card though, unless you want to go for additional ports. Don't be mislead though, the only ports you can make use of in a working system are the serial ports and the parallel port. All other ports find their limit defined in the BIOS and can only be enabled if a device on the motherboard fails and has been disabled.
From the earliest beginnings of personal computer systems until now, every computer has at least two serial ports and one parallel port. AT motherboards provide the connectors in which the ribbon cables plug it, whereas ATX boards feature the ports as part of the board. Serial data transmission uses a single wire which addresses each BIT of a transmission sequence individually. The transmission speed is therefore measures in bits per second (baud). The maximum transmission rate of a standard RS-232 serial port is 115200 baud. The actual connector in which you plug your serial device (i.e. modem, comms cable, et.) is a male 9 pin or 25 pin D-type connector. Parallel data transmission works basically just line serial data transmission, but instead of addressing one BIT at a time, it addresses one BYTE at a time. As you know, one BYTE has eight BITs, making the data transmission of the parallel port eight times faster than the serial ports. The maximum throughput, however, is limited to 512kbps. Parallel ports use a female 25 pin D-type connector.
USB (Universal Serial
Bus) is a newer input/output
specification than serial and parallel, but it does essentially the same
job, only much better. Serial and parallel signals get lost within very
short distances, and daisy chaining only two or three devices can already
cause difficulties and conflicts as each device still wants its own
interrupt. USB allows up to 127 devices to run at the same time on the
bus, with hubs connecting the devices to the bus and all devices happily
sharing one single interrupt. USB also provides a much higher
transfer The reason why USB works in two speed modes are the speeds of the various devices that will use the standard. Keyboards, mice and joysticks are among the low speed devices and work happily with 1.5Mbps. Zip drives, scanners and printers are among the high-speed devices and need throughput rates of up to 12Mbps. USB is also designed to meet Microsoft PnP (Plug and Play) specification, meaning users can install, and hot-swap devices without long installation procedures and reboots. Within the next few years USB will replace the traditional serial and parallel ports.
FireWire was originally developed by Apple as a technology for Local Area Networks, but it was soon realised that it was much more useful as a digital interface for connecting PC peripherals. So Apple handed FireWire over to the Institute of Electrical and Electronical Engineers (IEEE1394). For a while it was seen as yet another technology set to enter mainstream computing in order to replace traditional serial and parallel transmission standards. It really found it's way into computing only for connecting digital video devices though. However, the throughput of 400Mbps has potential enough for it to be reckoned with. For now, FireWire/DV editing is clearly the future of video. With DV (Digital Video) you get perfect copies and perfect video quality. All you need is a FireWire plug in card, but at the moment they still cost hundreds of pounds and are only aimed at the professional market or those of you with big pockets. Don't give up on FireWire though. It's been slow catching on for a few years, but with proposals before the IEEE to increase throughput to the order of gigabits per second and increased cable length, it looks as though IEEE1394 will be the interface of the future.
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A completely new approach to mouse
technology has recently been awarded with great success. Microsoft's
IntelliMouse Explorer is the first generation of a completely new mouse
breed. Microsoft have done away with the traditional ball and implemented
an optical sensor which scans the surface of the desktop at a rate of 1500
times per second. A digital Signal Processor compares the tiny changes of
the scanned images and translates them into cursor movement on the screen.
Using a sensor instead of a ball means that the IntelliMouse Explorer is
the first mouse without any moving parts. No more cleaning, no more
worrying about breadcrumbs on the desktop and good bye mouse mat.
Additionally, Microsoft have implemented five programmable buttons
(including the now obligatory wheel) and a neon-glowing underbelly.
The IntelliMouse Explorer is a
major breakthrough in mouse technology and will no doubt revolutionise
your desktop.
Scanners are not that much different than digital cameras, in
that both use light sensitive pixels to read the image. The digital camera
exposes the pixel plate to the object to be photographed, the scanner uses
its own light source in order to achieve and exposure. Also, as with
digital cameras, the maximum resolution and colour depth of scanners
depend on the amount of light sensitive elements used for scanning. A
scanner with 600 light sensor elements will scan at a maximum of 600dpi
resolution, which the scanning software can further enhance.
rates than the traditional RS-232 or
parallel-port devices. The dual-speed data transfer of USB delivers 1.5Mbps at low data transfer rate and
12Mbps at high data transfer rate, and it even can provide a maximum 500mA
of current to devices attached on the bus.
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