Hardware budgets are feeling the pinch of our tepid economy, and many companies are making employees use their laptops longer. If you are starting to tell your folks to keep plugging along with their laptops for four or five years instead of just three, you might be running into an unexpected expense: dead laptop batteries.

Well, to be fair, your laptop’s batteries probably aren’t completely dead. But since Lithium Ion batteries tend to lose about 20% of their capacity each year, a typical three-year-old laptop might only get about an hour or so on a charge, which might not even get your folks through an entire meeting. Here are four simple tips to forestall the day that you need to replace those batteries:

Keep it cool. Heat is the primary killer of batteries. Tell your employees to be careful not to let their laptops overheat. One common way that happens is packing a running laptop into a backpack or briefcase. If the laptop fails to go to sleep (and let’s face it — sleep glitches are common), then the laptop can get crazy hot in an enclosed space. You can almost smell the loss of battery longevity.

Recondition your battery regularly. Most laptop manufacturers (except Apple) don’t generally tell you about this, but a simple process known as reconditioning (or occasionally, recalibrating) can breathe new life into your laptop battery and add capacity back. To do that, turn off your screen saver and any other power management tools which put your PC to sleep. Fully charge the laptop, and then let it run all the way down — right until it powers down due to lack of juice. Then charge it back up again and restore your power management stuff. Do this every few months (such as three times a year).

Remove it when you’re not using it. When you leave your laptop plugged in at your desk all day every day, the battery never gets a chance to discharge and recharge — which is critical to its long-term health. Thankfully, there’s a simple solution: Remove the battery. As long as your laptop is connected to AC power, the battery isn’t necessary; it’ll run without it. Just remember to pop it back in before you take your laptop on the go.

Start with a super-sized battery. When you purchase your next round of laptops, upgrade to the extended-life battery. Not only will it give you significantly longer runtime to start with — great for road warriors and anyone else who works away from the office a lot — but the inevitable loss of battery life will have a less pronounced effect. The added cost of the larger batteries is worth the investment, because they end up lasting significantly longer.

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1 – Keep Your Desktop and Hard Disk Tidy

Is your computer desktop your virtual dumping group? Storing files and/or lots of shortcuts on your computer’s desktop will demand more memory from the computer. It is ok to keep some commonly used items here (or better yet shortcuts) but don’t make a habit of sprawling out all of your work on the Desktop. If you deal with a lot of documents or files on a regular basis, create a temporary work folder instead of littering the desktop.

If you are big on downloading software, videos or music, be sure to clean up after yourself. Don’t leave setup programs or media files on your hard disk that you are never going to use again; this just wastes your computer’s valuable disk space. Likewise, do not let your recycle bin or various temporary file folders fill up and fill your hard disk. If your disk space gets too low for any of these reasons, performance problems are sure to follow.

To easily empty your recycle bin and various temporary file folders, such as your temporary Internet folder, use Window’s build in “Disk Cleanup” utility. Access the “Disk Cleanup” utility by clicking:

Start – > All Programs – > Accessories – > System Tools – > Disk Cleanup

The tool is very easy to use; simply check the boxes next to the categories of files you would like to remove from your computer. There is one option to avoid however: “Compress Old Files”. This is meant to save disk space if a drive is running very low, but for this option, saved space is traded for performance.
2 – De-fragment Your Hard Disk Regularly

The way your computer stores files to the hard disk is a lot less pretty than what you see in your Windows Explorer file browser. The Windows operating system translates the digital mess of what is actually recorded on your hard disk so you can understand it. It also translates your clicks, drags and keystrokes into instructions the hard disk understands. The hard disk is read and written to in a sequence and through references rather than through the directory tree structure you may be familiar with. There are also many hidden files and some abstract data recorded to your hard disk that Windows constantly accesses.

Over time, with perpetual reads and writes to the hard disk, the way that the data is organized there becomes less and less efficient. For example, a digital photo you have saved may be split up into a dozen or more segments and an instruction set for associating and locating those pieces. YES! WHAT A MESS! Also, files that your computer needs to access very frequently may be stored on a part of the hard disk that is the slowest to read, while your report on Dinosaurs from the 3rd grade (or some other equally obscure file you’ll never look at again) is stored on the fastest part of the disk. When your hard disk gets in this gross state of disorder it is said to be fragmented, and your computer begins to crawl.

Fortunately, Windows has a built in tool, “Disk Defragmenter”, which can correct the data fragmentation on your hard disk fairly quickly. The tool can be accessed by clicking:

Start – > Programs – > Accessories – > System Tools – > Disk Defragmenter

The program is very easy to use. Once you have started “Disk Defragmenter”, all you have to do is click the “Defragment” button and let it do its magic. The time the process takes to complete depends on how bad the fragmentation of your hard disk is. If you have not “defragged” your hard disk before, you will probably see an improvement in your computers performance as soon as the process is complete.

Note: Complete Step 1 before defragmenting your hard disk since there is no sense in rearranging data you are going to delete anyway. Failing to do so will also unnecessarily slow down the defragmentation process.

Note: You can defragment your hard disk as often as you like. The more often you do so, the less time it will take.
3 – Keep Your Computer Free from Viruses (and other unwanted software)

If you are connected to the Internet, it is just too easy to come into contact with malicious computer viruses. Some viruses will slow down your computer and maybe corrupting your favorite files, while others will complete destroy your computer’s software and render the machine useless. Therefore, it is essential that your computer be equipped with modern anti-virus software. There are many anti-virus packages to choose from, so consult with friends and hit the web to see which packages people have had the most success with.

Whether you pick a brand name or opt for a freebee, make sure you keep the anti-virus software’s “definitions” up to date. Virus definitions let the anti-virus software distinguish known viruses from other software. New virus threats are constantly emerging, so it is essential for your anti-virus software to have a feature that regularly updates these definitions.

Computer viruses are not the only annoyances that can plague your computer experience. Two other groups of unwanted software, adware and spyware, can slow down your system. These types of software are not technically viruses because their purpose is not purely malicious. Adware is designed to advertise products and services to you through your computer, while spyware is designed to capture information from your system and transmit it to someone else. Obviously, you do not want any of this software running on your computer, irregardless of the fact that it will contribute to a computer’s sluggish performance.

Some anti-virus software packages are bundled with anti-adware and spyware software, and there are other packages solely devoted to detecting and removing this type of software. Again, do some research because there are many choices. As with the anti-virus software, these detection and removal tools need to be kept up to date to be effective.
4 – Make All of the Above Easy

Even if you are fairly technically savvy, but especially if you’re not, you probably wondering, “how often do I have to do ALL of that?”, and “will it be worth it?” Well, you can make sure all of these things get done everyday, or even more often, with just a little up-front work. “Set it and forget it” sort-to-speak.

Everything mentioned in steps 1 through 3 can be automated using Window’s built in feature to schedule tasks, and a simple batch file. Batch files contain a set of instructions for your computer to follow, which can be called upon at a specific and recurring time by Window’s “Scheduled Tasks” manager.

How to Create a Batch Files:

To create a batch file:
Click Start – > Run
Enter “notepad”
Click “Ok”.

The notepad editor will appear.

Type out the commands you want completed, in order and each on a separate line.
(Specific commands will be mentioned below)

Next, save the file by clicking:

File – > Save

Save the file to a location and with a name you will remember. As an example, you could save the file under “C:\” and call it “maintenance.bat”.
Be sure to change the “save as type” from the default of “Text Documents” to “All Files”, and to include the “.bat” as part of the filename.
5 – Automatic Disk Cleanup:

So that “Disk Cleanup” can be included in your automated maintenance, you must first set the options you would like the “Disk Cleanup” utility to use when “Scheduled Tasks” executes it. To set these options:

Click Start – > Run
Type “cleanmgr /sageset:1″
Click the “ok” button

The “Disk Cleanup Settings” windows will appear.
Check off the items you want automatically cleaned up, as described in step 1 above.

Click the “ok” button

The settings are now saved.

To include “Disk Cleanup” in your automated process, save the command “cleanmgr /sagerun:1″ in your batch file.
6 – Automatic Defrag:

Including a hard disk defrag in your automated process simply requires another entry in your batch file. Include a line that reads, “defrag c:” in the batch and you are done. Remember to include this line after the “Disk Cleanup” command, as this will speed up your whole maintenance process.
7 – Stay Virus Free:

The specifics on how to include regular definition updates and scans for viruses, adwares and spywares is entirely dependant on the programs you have chosen for these tasks, but most can usually be initiated from a batch file. Consult with your vendors’ websites or support staff. If any of these products cannot be initiated from your batch file, they probably have a built in means of scheduling the same important tasks.
8 – Schedule It!:

Once your batch file is complete, you can easily test it. Simply double click the batch file and it should complete all of the tasks you included. Note that it may take some time for the process to complete. If you have trouble, it may help to add the command “pause” at the end of the batch file so you can see where you went wrong.

If there is no convenient and regular time for you to schedule your batch file, you can continue to manually execute just as you did to test it. Another option is to include the command, “shutdown -s -f” at the very end of the batch file, which will turn off your computer after all of the commands are complete. Each time you are done using your computer for the day, close all of your programs and double click your batch file; your computer will take care of its maintenance and then power-down.

If there is a convenient time for your maintenance to be performed, perhaps in the middle of the night if your computer is left on, you can use Window’s “Scheduled Tasks” feature to make your batch file execute automatically at that time. When scheduling, remember to allow enough time for all of the tasks to complete before you will need to use the computer again.

To schedule a task in Windows click:

Start – > All Programs – > Accessories – > System Tools – > Scheduled Tasks
Double-Click “Add Scheduled Task”
Click “Next”
Click “Browse”
Locate and select your batch file
Click “Open”
Select how often you would like your batch file executed
Click “Next”
Select the time you would like the batch file executed
Click “Next”
Enter the username and password for your computer if you have one
Click “Next”
Click “Finished”

The tasks you have defined will now run on a regular basis as you have specified. If you have included all of the tasks suggested above, you computer should run relatively trouble free for years to come.

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An optical mouse uses a light-emitting diode and photodiodes to detect movement relative to the underlying surface, unlike wheeled mice which use a set of one rolling ball and two chopper wheels for motion detection.

Early optical Mice

Early optical mice, first demonstrated by two independent inventors in 1980, came in two different varieties:

Some, such as those invented by Steve Kirsch of MIT and Mouse Systems Corporation, used an infrared LED and a four-quadrant infrared sensor to detect grid lines printed with infrared absorbing ink on a special metallic surface. Predictive algorithms in the CPU of the mouse calculated the speed and direction over the grid.

Others, invented by Richard F. Lyon and sold by Xerox, used a 16-pixel visible-light image sensor with integrated motion detection on the same chip and tracked the motion of light dots in a dark field of a printed paper or similar mouse pad.

These two mouse types had very different behaviors, as the Kirsch mouse used an x-y coordinate system embedded in the pad, and would not work correctly when the pad was rotated, while the Lyon mouse used the x-y coordinate system of the mouse body, as mechanical mice do.
Modern Optical Mice

Modern surface-independent optical mice work by using an optoelectronic sensor (essentially, a tiny low-resolution video camera) to take successive images of the surface on which the mouse operates. As computing power grew cheaper, it became possible to embed more powerful special-purpose image-processing chips in the mouse itself. This advance enabled the mouse to detect relative motion on a wide variety of surfaces, translating the movement of the mouse into the movement of the cursor and eliminating the need for a special mouse-pad.

The first commercially successful optical computer mouse was the Microsoft IntelliMouse® with IntelliEye™, introduced in 1999 using technology developed by Hewlett-Packard. It worked on almost any surface, and represented a welcome improvement over mechanical mice, which would pick up dirt, track capriciously, invite rough handling, and need to be taken apart and cleaned. Instead the reliable performance of the IntelliMouse® allowed relaxed grips which also were less likely to cause repetitive strain injury. Other manufacturers soon followed Microsoft’s lead using components manufactured by the HP spin-off Agilent Technologies, and over the next several years mechanical mice became obsolete.

The technology underlying the modern optical computer mouse is known as digital image correlation, a technology pioneered by the defense industry for tracking military targets. Optical mice use image sensors to image naturally occurring texture in materials such as wood, cloth, mouse pads and Formica. These surfaces, when lit at a grazing angle by a light emitting diode, cast distinct shadows that resemble a hilly terrain lit at sunset. Images of these surfaces are captured in continuous succession and compared with each other to determine how far the mouse has moved.

To understand how optical mice work, imagine two photographs of the same object except slightly offset from each other. Place both photographs on a light table to make them transparent, and slide one across the other until their images line up. The amount that the edges of one photograph overhang the other represents the offset between the images, and in the case of an optical computer mouse the distance it has moved.

Optical mice capture one thousand successive images or more per second. Depending on how fast the mouse is moving, each image will be offset from the previous one by a fraction of a pixel or as many as several pixels. Optical mice mathematically process these images using cross correlation to calculate how much each successive image is offset from the previous one.

An optical mouse might use an image sensor having an 18 x 18 pixel array of monochromatic pixels. Its sensor would normally share the same ASIC as that used for storing and processing the images. One refinement would be accelerating the correlation process by using information from previous motions, and another refinement would be preventing deadbands when moving slowly by adding interpolation or frame-skipping.

The invention of the modern optical mouse at HP was made more likely by a succession of related projects during the 1990s at its central research laboratory. In 1992 John Ertel, William Holland, Kent Vincent, Rueiming Jamp and Richard Baldwin were awarded US Patent 5,149,980 for measuring paper advance in a printer by correlating images of paper fibers. In 1998 Travis N. Blalock, Richard A. Baumgartner, Thomas Hornak, and Mark T. Smith were awarded US Patent 5,729,008 for tracking motion in a hand-held scanner by correlating images of paper fibers and document features, a technology commercialized in 1998 with the HP 920 Capshare handheld scanner. In 2002 Gary Gordon, Derek Knee, Rajeev Badyal and Jason Hartlove were awarded US Patent 6,433,780 for the modern optical computer mouse using image correlation.
Laser Mice

The laser mouse uses an infrared laser diode instead of a LED to illuminate the surface beneath their sensor. As early as 1998, Sun Microsystems provided a laser mouse with their Sun SPARCstation servers and workstations. However, laser mice did not enter the mainstream market until 2004, when Paul Machin at Logitech, in partnership with Agilent Technologies, introduced its MX 1000 laser mouse. This mouse uses a small infrared laser instead of an LED and has significantly increased the resolution of the image taken by the mouse. The laser enables around 20 times more surface tracking power to the surface features used for navigation compared to conventional optical mice, via interference effects.

Glass laser (or glaser) mice have the same capability of a laser mouse but can also be used on top of mirror or transparent glass with few problems.

In August 2009, Logitech introduced mice with two lasers, to track on glass and glossy surfaces better; they dubbed them “dark field” mice.
LED Color

The color of the optical mouse’s light-emitting diodes can vary, but red is most common, as red diodes are inexpensive and silicon is very sensitive to red light. Other colors are sometimes used, such as the blue LED of the V-Mouse VM-101 illustrated at right.
Power

Manufacturers often engineer their optical mice—especially battery-powered wireless models—to save power when possible. In order to do this, the mouse dims or blinks the laser or LED when in standby mode (each mouse has a different standby time). This function may also increase the laser / LED life. Mice designed specifically for gamers, such as the Logitech G5 or the Razer Copperhead, often lack this feature in an attempt to reduce latency and to improve responsiveness.

A typical implementation in Logitech mice has four power states, where the sensor is pulsed at different rates per second:
- 1500: full on condition for accurate response while moving, illumination appears bright.
- 100: fallback active condition while not moving, illumination appears dull.
- 10: standby
- 2: sleep state

Some other mice turn the sensor fully off in the sleep state, requiring a button click to wake.

Optical mice utilizing infrared elements (LEDs or lasers) offer substantial increases in battery life. Some Logitech mice, such as the V450 848 nm laser mouse, are capable of functioning on two AA batteries for a full year, due to the low power requirements of the infrared laser.
Optical Versus Mechanical Mice

Unlike mechanical mice, which can become clogged with lint, optical mice have no rolling parts; therefore, they do not require maintenance other than removing debris that might collect under the light emitter. However, they generally cannot track on glossy and transparent surfaces, including some mouse-pads, sometimes causing the cursor to drift unpredictably during operation. Mice with less image-processing power also have problems tracking fast movement, though high-end mice can track at 2 m/s (80 inches per second) and faster.

Some models of laser mice can track on glossy and transparent surfaces, and have a much higher sensitivity than either their mechanical or optical counterparts but are more expensive than their LED based or mechanical counterparts.

As of 2006, mechanical mice have lower average power demands than their optical counterparts. In practice this is only significant when the mouse is either used with a battery-powered computer, such as a notebook model, or is a battery-powered wireless mouse.

Optical models will outperform mechanical mice on uneven, slick, soft, sticky, or loose surfaces, and generally in mobile situations lacking mouse pads. Because optical mice render movement based on an image which the LED (or infrared diode) illuminates, use with multicolored mouse pads may result in unreliable performance; however, laser mice do not suffer these problems and will track on such surfaces. The advent of affordable high-speed, low-resolution cameras and the integrated logic in optical mice provides an ideal laboratory for experimentation on next-generation input-devices. Experimenters can obtain low-cost components simply by taking apart a working mouse and changing the optics or by writing new software.

The Basic Idea

Webcams, like most things, range from simple to complex. If you understand the essence of a simple Webcam setup, increasing the complexity is only a matter of adding functionality through software, custom code and/or equipment connections.
A simple Webcam setup consists of a digital camera attached to your computer, typically through the USB port. The camera part of the Webcam setup is just a digital camera — there’s really nothing special going on there. The “Webcam” nature of the camera comes with the software. Webcam software “grabs a frame” from the digital camera at a preset interval (for example, the software might grab a still image from the camera once every 30 seconds) and transfers it to another location for viewing. If you’re interested in using your Webcam for streaming video, you’ll want a Webcam system with a high frame rate. Frame rate indicates the number of pictures the software can grab and transfer in one second. For streaming video, you need a minimum rate of at least 15 frames per second (fps), and 30 fps is ideal. To achieve high frame rates, you need a high-speed Internet connection.

Once it captures a frame, the software broadcasts the image over your Internet connection. There are several broadcast methods. Using the most common method, the software turns that image into a JPEG file and uploads it to a Web server using File Transfer Protocol (FTP). You can easily place a JPEG image on any Web page (for information on creating Web pages and adding JPEG images, see How Web Pages Work).

If you don’t have your own Web server, lots of companies offer you a free place to upload your images, saving you the trouble of having to set up and maintain a Web server or a hosted Web site.

This is the simplest possible Webcam. Let’s see what you need to make it happen.

What You Need

In order to create a simple Webcam, you need three things:

•A camera of some sort connected to your computer
•A piece of software that can grab a frame from the camera periodically
•A way to broadcast your images on the Web

If you have your own Web server and Web site, you already have a way to post your Webcam images on the Web. At its most basic, a Web server is simply a piece of hardware that has the ability to deliver Web-based content to a Web browser. For some people, their home computer serves as their Web server. If that’s the case, a camera, a piece of software and your PC are all that you need. If you want to use a Web server that’s hosted elsewhere (for example, if you’re paying an ASP to host your Web server), you also need:
•The ability to move frames from your computer to the Web server, typically by File Transfer Protocol (FTP). For most Web servers, this is no problem; but occasionally, a hosting company will have policies in place that make this difficult.

•A relatively consistent connection between your computer and the Internet. A modem connection to an ISP is fine if it is something that you keep connected most of the time, which implies that you have a dedicated phone line for your computer. If you have something like a cable modem that is connected all the time, that’s perfect.
If you don’t have a Web server or a Web site, and you don’t want one, you can simply have someone else maintain your Webcam images. Lots of Webcam software comes complete with Web-based image access. They usually offer different access options, including remote access, which utilizes UDP protocol to transfer your Webcam images directly from your computer to another computer. This can be done:

•via Web browser, in which case the software itself establishes its own HTTP server so anyone using a Web browser can access the Webcam images on your PC
•via traditional FTP upload to a remote Web server
By using this type of service, you avoid having to host and/or maintain your own Web site. If you are using one of these services and you want the image to refresh itself constantly, you need a relatively consistent connection between your computer and the Internet. If your connection is not consistent, it won’t hurt anything. It just means that the image won’t always be up to date.

Setting It Up

In order to experiment with Webcams and go through the process of setting one up, HowStuffWorks got itself a Webcam. To set it up, here is what we did:

1.We went down to the local computer warehouse and bought the Intel Pro Video PC Camera.

2.We installed the software for the camera on a Windows XP machine.
3.We went to the Web site www.webcam32.com and downloaded a program called Webcam32. This is a popular software package for Webcams. You can get a free demo version or pay $39.95 for the full version. We went ahead and paid for a registered copy. (The complete user’s manual for this product is available on the Web site. Check it out to see the wide array of features available on today’s Webcam software.)

4.We installed Webcam32. It was a very easy installation.
5.After entering the address of the FTP site and a couple of other pieces of information, the Webcam showed its first signs of life!

6.We pointed the camera out the window.
7.We then tuned the software a bit to reduce the file size of the images and to enable the temporary-file copying feature.

There are many different features you can experiment with in Webcam32: streaming video, chat, captions, AVI files and different resolutions and compression ratios, to name a few. Webcam32 also supports the AutoCam feature, which allows you to create a Web page for your Webcam for free on the company’s server. The software makes it simple.
As you can see, setting up a basic Webcam is extremely easy. If nothing else, the setup described here is a fun, inexpensive and simple way to experiment with a Webcam and see what you can do with one of your own!

Advanced Features

Once you manage the simple system, you can look into other Webcam features and settings like:

•Motion sensing – The Webcam takes a new picture when it detects motion.
•Image archiving – You can create an archive that saves all of your Webcam images or only certain images at pre-set intervals.
•Video messaging – Some instant messenger programs support Webcam video.
•Advanced connections – Use wired or wireless methods to connect your home-theater A/V equipment to your Webcam.
•Automation – Robotic cameras let you set a series of pan/tilt positions and program frame-capture settings based on the position of the camera.
•Streaming media – For professional applications, a Webcam setup can use MPEG4 compression to achieve true streaming audio and video (this is the compression system used in most of the popular PC-based media players).
•Custom coding – Import your own computer code to tell the Webcam what to do.

One example of custom coding is a set of commands that makes a Webcam image automatically refresh. The simple Webcam system we’ve set up in this article produces a static image. Users have to refresh the image manually (by pushing the Refresh button in the browser) if they want to see any changes. There are three different techniques you can use to create automatic refreshing:

•You can add a meta tag to the HTML for the page so that the page refreshes at some frequency. The tag to add is:

<meta http-equiv=”refresh” content=”30″>

The “30″ is the number of seconds between each refresh and can be set to anything you like. The entire page will reload every 30 seconds, so it is beneficial to keep the page short.

•You can add a Java applet to your site. The Webcam32 and Java Applets page explains how to obtain and install the free applet. The applet is a program that automatically fetches the image periodically. The advantage is that only the image refreshes, not the entire page. Most browsers support Java applets, so most of your viewers will have no problem.

•You can use JavaScript, as demonstrated on The JavaScript Source: Refresh (look at the source code on this page). You can also check out How Java Works for a detailed look at Java programming.

Webcam Networking

One problem with using a camera hooked to a computer via a USB cable is the limited cable length. What if the room you want to capture is at the other end of the house, or outside? In that case, you need to purchase a camera with external connections. You have a few options:

•You can place a standard camera anywhere in the house and run a video cable with RCA jacks on it from the camera to the computer. There are all sorts of places on the Web that sell small pinhole video cameras, either on their own or embedded in things like clocks and smoke detectors. You can find small security cameras for less than $100. (Click here to use the HowStuffWorks search engine to search for security cameras.)

•You can avoid the cable by using a radio link (X10: XRay Vision is one example of this type of product), an Ethernet connection or a WiFi setup. If you already have a home network, connecting an external Webcam to your computer probably won’t require any additional networking.

Monitoring your home and sharing images via the Web are only a couple of the things you can do with your Webcam. There are any number of ways to make use of a camera that’s connected to your computer. You can get software that will let you make video phone calls with a friend who also has a Webcam. You can hold a video-conferencing session with business associates on the other side of the world. You can conduct a video interview and broadcast it live on your blog. Some Webcam software will even deliver images directly to your Web-enabled PDA or smartphone. Other products let you connect your camcorder to your Webcam setup so you can let everybody watch your vacation footage via the Internet. The possibilities are endless.

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LED TV’s and monitors are part of the new High Definition generation. Quite simply, LED (Light Emitting Diode) technology uses individual backlights which in many cases can be tuned on or off in areas to allow for precision control of the lighting emitted from the TV screen or monitor. This differs from traditional backlighting which uses a CCFL (Cathode Fluorescent Lamp) that involves several fluorescent tubes placed horizontally across the screen. The enhanced benefits of LED technology allow for a sleeker screen design plus improved brightness potential, colour reproduction and viewing contrast.

The following guide will help you get to grips with LED technology so you can decide for yourself whether it deserves the must-have hype.

Types of LED Lighting

The first thing to understand is that there are two distinct types of LED TV screens or monitors based on how the LED backlighting is arranged:

Edge-lit screens

This type of TV screen or monitor has a row of LED backlights placed around the edges of the screen panel, which shine into a multi-layered diffuser panel creating a uniform view. Because the lights surround the perimeter of the screen instead of being behind it, edge-lit models allow for an ultra sleek design.

Full-matrix screens

These models have their LED lights arranged across the back of the display, which then feed through a diffuser panel to make the backlighting even. The most effective LED TV’s or monitors of this range have a feature called ‘local dimming’ or ‘smart dimming’ – this allows you to dim or switch off particular sections of the lighting elements while leaving other areas at full brightness. The result is enhanced picture contrast of black levels and other colours. It must be said that without this ability to fine tune the LED lighting to your tastes, LED TV’s are generally very similar to traditional LCD TV’s.

LED Viewing Quality

Colours

For on-point colour accuracy, LED TV’s and monitors with coloured backlighting are the best option. The display is still impressive however with the other type of LED lights which are white.

Definition & Contrast

As explained above, LED TV and monitors with the ‘local dimming’ feature gives you the power to control the backlighting arrangement for an improved picture quality in terms of definition and colour contrast. The result of being able to dim or switch off certain sections of the LED lights allows for darker blacks and enhanced definition while viewing dark-lit images. The other models that don’t have this feature are still high in viewing quality to the eye of the average person, but a true visual connoisseur will notice that uniform LED backlighting causes some areas of the screen to be better lit than others.

Angle of View

Because of the flat screen used by LED technology, it must be noted that this design suffers slightly from contrast degradation when the screen or monitor is viewed at angles of more than approximately 30 degrees from the centre. This issue has been significantly improved on over the past few years and has now advanced sufficiently to offer better viewing quality than plasma screens.

Size and Cost of LED TV’s

Televisions with LED backlights are currently on offer in sizes that range from 46 to 70 inches. While they generally cost a fair amount more than their traditional LCD television counterparts, many people are happy to pay the extra cost to have the best picture quality possible.

Life Expectation

As a general rule of thumb, TV manufacturers say their products have the longevity of approximately 100 000 hours. Since LED TV’s are quite new to the marketplace, this life expectation has not been fully confirmed as yet, however LED lights are known to last for a reasonably long period of time. LED backlighting technology is also said to suffer less degradation in colour over time than LCD models.

Power Usage

LED backlights offer better energy efficiency than CCFL-based backlights. It must be said however that a LED TV with the local dimming feature will use more electrical power than a traditional or edge-lit LCD TV that has the same screen size.
Whether you’re looking to buy a LED TV or LED monitor, the above information gives you the key facts about this new technology so you can make the right choice when shopping around for your viewing needs. As there are now an increasing amount of models available from different manufacturers, it’s crucial to do your research so you can be sure of finding the manufacturer and model that offers the best quality for your money.

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The cd-rom is an external support for memory, with superior characteristics than floppy disk drives. Cd-rom stands for Compact Disk Read Only Memory and has special facilities, because of the updated fabrication techniques and the way of organizing and data accessing.

The stocking and data accessing is easily obtained using high speeds optical techniques, that’s why the number of mechanical components is little and the reliability is high.

Cd-rom history began in 1980, when this activity domain started to grow as a result of collaboration between Philips and Sony. Before that, each of them tried to provide a solution, but after the collaboration start, they set the standards of cd-rom (in 1982).

Cd-rom and audio CD are similar, only they have to deal some differences. The base is the same, also the reading principle, the physical format and the capacity. The differences are in the field of informational contents, and also in the hardware that reads and writes.

An audio CD can be easily read by the hardware of a CD-ROM.

The main performances of a CD-ROM:

- stocking capacity;

- access time;

- transfer rate;

- working speed.

The stocking capacity

A CD-ROM has a 650 MB capacity, much more than the diskette, but less than the HDD.

The access time

The access time is the time that occurs between the read or write request and the starting operation. This is defined as in the HDD case (<20ms), only that cd-rom access time is greater: between 100ms and 400ms, maybe less than 100ms. The great access time is the explanation of the fact that every accessing needs to get the CD to a certain rotation speed. The HDD has a constant rotation speed.

The CD-ROM reading head is a little bit heavier than the HDD’s one, because it contains lots of components: the laser, the photo cell etc.)

The transfer rate

This is the amount of information that is transferred in a second. It can be between 150KB and >3000KB (at the modern units). The transfer rate depends on the access time and the working speed of CD unit.

CD-ROM

The working speed

This is the parameter that directly influences the transfer rate and the access time. The working speed is set according to the first type of CD-ROM unit, which was named single speed and which has a transfer rate of 150 KB/sec. After that the 2x, 4x and so on came out.

The CD-ROM is superior to the diskette, but also has some disadvantages. It permits only the reading operation. For a writing operation, you must have a CD-writer unit.

The stocking capacity of a CD-ROM is sometimes not enough. Many programs or games have greater dimensions. There are encyclopedias or applications that need four or five CDs. This is not a problem anymore, because another support came out, the DVD – the next step from the CD-ROM.

DVD-ROM

The DVD-ROM technology has already replaced some of the video cassettes. A DVD looks exactly like the usual CD, only that the points containing binary information (0 and 1) are little, and the space between them is smaller. That is why a DVD can stock 4,7GB of information.

On a DVD you can use the both sides for your information, so you gain another 4,7 GB of information.

The future promises a disk with many inside layers to stock as many as 15GB.

The DVD-ROM is better, because you can add segments of information and has a better quality of video and sound than the CD-ROM.

To read the DVD-ROM you need a DVD-ROM unit that looks exactly like the CD-ROM unit. It has two lasers: one for the CDs and the other for DVDs.

The great capacity of DVD is important for stocking pictures and sound with a high quality. The Hollywood actually has an important role from the beginning of DVDs, because they started to release movies on DVD support, not only on video cassettes. mportant role from the beggininng.sound with a great qualityound than the CD-ROM

You need a Video-DVD decoding device to view the Video-DVDs. This device works simultaneously with the video device of your PC. A stronger PC doesn’t need a separate device to fulfill these needs, because the whole activity is set by the processor.

You can write information on a DVD-ROM, or you can even erase it. This happens when you need to free space on your HDD.

The DVD history starts in 1990 when the Japanese corporation – Sony – collaborated with Philips to create a new digital disk (Digital Versatile Disk) with a greater capacity. Other corporation didn’t agree with the standard set by those two, trying to find a better standard. Sony and Philips agreed and opted to licentiate the results of the global corporation.

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Function keys are that row of keys along the top of your keyboard labeled F1 through F10 (or F12, depending on the keyboard). These keys have flexible definitions and can be redefined by an application or operating system. Function keys typically carry out popular or repetitive tasks, saving you from having to type (or remember) several commands or keystrokes.

The Function Keys And You
In Microsoft Windows, key functions vary from application to application. There is, however, some common functionality between programs. Common function key tasks include:

F1: The F1 key is almost universally used to access help files. By pressing WINDOWS KEY + F1, you can access the Windows help and support center.
F2: The F2 key is used to rename the selected file or object.
F3: The F3 key is often used to access the search function of an application. On the desktop, F3 will call up the detailed Search Results window.
F4: Typing ALT + F4 will close the currently active program.
F5: This key will refresh the contents of a dialog box (e.g., Save As). In most browsers, F5 will refresh the currently displayed Web page.
F7: Sometimes used to call the Spell Check function of an application. Microsoft Word and Open Office both support this command.
F10: The F10 key makes a program’s Menu Bar active. SHIFT + F10 will display an item’s shortcut menu-the equivalent of right clicking on an item.
F11: This key is used in most browser programs to switch into full-screen mode

A Trick with Windows Function Keys
Windows doesn’t use all of the function keys. You can take advantage of this by assigning a program to an “empty” function key. F8, F9 and F12 are good candidates. To assign a function key, follow these steps:

Right click on the program’s shortcut, either on the desktop or in the Start menu.
Click on the Shortcut tab.
Click on the Shortcut Key text box.
Press the function key you want to assign to the program. The function key name will appear in the text box.
Click Apply or Ok and close the dialog box.

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Different usb connectors. From left to right: male Micro USB B-Type, proprietary (not USB), male Mini USB (5-pin) B-type, female A-type, male A-type, male B-type. Shown with a centimeter ruler. Female A-type connector (4th from left) is "upside down" to show the pins.

There are several types of USB connectors, including some that have been added while the specification progressed. The original USB specification detailed Standard-A and Standard-B plugs and receptacles. The first engineering change notice to the USB 2.0 specification added Mini-B plugs and receptacles.

The data connectors in the Standard-A plug are actually recessed in the plug as compared to the outside power connectors. This permits the power to connect first which prevents data errors by allowing the device to power up first and then transfer the data. Some devices will operate in different modes depending on whether the data connection is made. This difference in connection can be exploited by inserting the connector only partially. For example, some battery-powered MP3 players switch into file transfer mode and cannot play MP3 files while a USB plug is fully inserted, but can be operated in MP3 playback mode using USB power by inserting the plug only part way so that the power slots make contact while the data slots do not. This enables those devices to be operated in MP3 playback mode while getting power from the cable.

To reliably enable a charge-only feature, modern USB accessory peripherals now include charging cables that provide power connections to the host port but no data connections, and both home and vehicle charging docks are available that supply power from a converter device and do not include a host device and data pins, allowing any capable USB device to be charged and/or operated from a standard USB cable.

Standard Type A and B

Standard USB connectors, types A and B

• Standard type AThe USB 2.0 Standard-A type of USB plug is a flattened rectangle which inserts into a “downstream-port” receptacle on the USB host, or a hub, and carries both power and data. This plug is frequently seen on cables that are permanently attached to a device, such as one connecting a keyboard or mouse to the computer via usb connection.USB connections eventually wear out as the connection loosens through repeated plugging and unplugging. The lifetime of a USB-A male connector is approximately 1,500 connect/disconnect cycles
• Standard type BA Standard-B plug—which has a square shape with bevelled exterior corners—typically plugs into an “upstream receptacle” on a device that uses a removable cable, e.g. a printer. A Type B plug delivers power in addition to carrying data. On some devices, the Type B receptacle has no data connections, being used solely for accepting power from the upstream device. This two-connector-type scheme (A/B) prevents a user from accidentally creating an electrical loop.

USB Mini and Micro connectors

Mini usb AB

Various connectors have been used for smaller devices such as PDAs, mobile phones or digital cameras. These include the now-deprecated (but standardized) Mini-A and the currently standard Mini-B, Micro-A, and Micro-B connectors. The Mini-A and Mini-B plugs are approximately 3 by 7 mm.

The micro-USB plugs have a similar width but approximately half the thickness, enabling their integration into thinner portable devices. The micro-A connector is 6.85 by 1.8 mm with a maximum overmold size of 11.7 by 8.5 mm. The micro-B connector is 6.85 by 1.8 mm with a maximum overmold size of 10.6 by 8.5 mm.

Micro B USB Plug

The Micro-USB connector was announced by the USB-IF on January 4, 2007. The Mini-A connector and the Mini-AB receptacle connector were deprecated on May 23, 2007. As of February 2009, many currently available devices and cables still use Mini plugs, but the newer Micro connectors are being widely adopted and as of December 2010, the Micro connectors are the most widely used. The thinner micro connectors are intended to replace the Mini plugs in new devices including smartphones and personal digital assistants. The Micro plug design is rated for at least 10,000 connect-disconnect cycles which is significantly more than the Mini plug design. The Universal Serial Bus Micro-USB Cables and Connectors Specification details the mechanical characteristics of Micro-A plugs, Micro-AB receptacles, and Micro-B plugs and receptacles, along with a Standard-A receptacle to Micro-A plug adapter.

The cellular phone carrier group, Open Mobile Terminal Platform (OMTP) in 2007 have endorsed Micro-USB as the standard connector for data and power on mobile devices. These include various types of battery chargers, allowing Micro-USB to be the single external cable link needed by some devices.

As of January 30, 2009 Micro-USB has been accepted and is being used by almost all cell phone manufacturers as the standard charging port (including HTC, Motorola, Nokia, LG, Hewlett-Packard, Samsung, Sony Ericsson, Research In Motion) in most of the world.

On June 29, 2009, following a request from the European Commission and in close co-operation with the Commission services, major producers of mobile phones have agreed in a Memorandum of Understanding (“MoU”) to harmonise chargers for data-enabled mobile phones sold in the European Union. Industry commits to provide charger compatibility on the basis of the Micro-USB connector. Consumers will be able to purchase mobile phones without a charger, thus logically reducing their cost. Following a mandate from the European Commission, the European Standardisation Bodies CEN-CENELEC and ETSI have now made available the harmonised standards needed for the manufacture of data-enabled mobile phones compatible with the new common External Power Supply (EPS) based on micro-USB.

In addition, on October 22, 2009 the International Telecommunication Union (ITU) has also announced that it had embraced micro-USB as the Universal Charger Solution its “energy-efficient one-charger-fits-all new mobile phone solution”, and added: “Based on the Micro-USB interface, UCS chargers will also include a 4-star or higher efficiency rating—up to three times more energy-efficient than an unrated charger.”

USB Micro-AB Socket OTG

An OTG device is required to have one, and only one USB connector: a Micro-AB receptacle. This receptacle is capable of accepting either a Micro-A plug or a Micro-B plug attached to any of the legal cables and adapters as defined in Micro-USB1.01.

The OTG device with the A-plug inserted is called the A-device and is responsible for powering the USB interface when required and by default assumes the role of host. The OTG device with the B-plug inserted is called the B-device and by default assumes the role of peripheral. An OTG device with no plug inserted defaults to acting as a B-device. If an application on the B-device requires the role of host, then the HNP protocol is used to temporarily transfer the host role to the B-device.

OTG devices attached either to a peripheral-only B-device or a standard/embedded host will have their role fixed by the cable since in these scenarios it is only possible to attach the cable one way around.

Proprietary connectors and formats

• Microsoft’s original Xbox game console uses standard USB 1.1 signalling in its controllers and memory cards, but uses proprietary connectors and ports. The Xbox 360 (pre Xbox 360 S) has two Memory Unit ports which are USB compliant with proprietary connectors.
• IBM UltraPort uses standard USB signalling, but via a proprietary connection format.
• American Power Conversion uses USB signalling and HID device class on its uninterruptible power supplies using 10P10C connectors.
• HTC manufactured Windows Mobile and Android-based Communicators which have a proprietary connector called HTC ExtUSB (Extended USB). ExtUSB combines mini-USB (with which it is backwards-compatible) with audio input as well as audio and video output in an 11-pin connector.
• Nokia includes a USB connection as part of the Pop-Port connector on some older mobile phone models.
• Sony Ericsson used a proprietary connector called FastPort from 2005 to 2009.
• The second, third, and fourth generation iPod Shuffle uses a TRRS connector to carry USB, audio, or power signals.
• iriver added a fifth power pin within USB-A plugs for higher power and faster charging, used for the iriver U10 series. A mini-USB version contains a matching extra power pin for the cradle.
• Apple has shipped non-standard USB extension cables with some of their computers, for use with the included Apple USB keyboards. The extension cable’s socket is keyed with a small protrusion to prevent the insertion of a standard USB plug, while the Apple USB keyboard’s plug has a matching indentation. The indentation on the keyboard’s plug does not interfere with insertion into a standard USB socket. Despite the keying, it is still possible to insert standard USB plugs into the extension cord. The protrusion can also be shaved off with an appropriate blade, or crushed with locking pliers.
• Apple also uses a proprietary USB 30-pin dock connector on its iPods, iPhones, and the iPad.
• HP Tablet computers use non-standard connectors to transmit the USB signals between the keyboard/mouse unit and the Computer Tablet Unit.
• PDMI (Portable Digital Media Interface) is a 30-pin docking connector for portable devices standardized by ANSI/CEA which includes USB 3.0 “SuperSpeed” and USB 2.0 “High/Standard Speed” with USB-on-the-go, as well as DisplayPort, HDMI CEC, 5 V power, and analog audio.
• Some digital cameras have their own USB connectors, like the Panasonic Lumix DMC-FT2.
• The United States Army’s Land Warrior system uses standard USB signalling with 15.6 V power using a ruggedized Glenair connector.
• The ExpressCard interface includes a USB2 port as well as the express bus port.

Pop-Port connector of an original Nokia HS-5 headse