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Dome-switch keyboard

Dome-switch keyboards are kind of a hybrid of membrane and mechanical keyboards. They bring two circuit board traces together under a rubber "dome" or bubble. The inside of the top of the bubble is coated in some conductive substance. When a key is pressed, it collapses the dome, which shorts out the two circuit traces and completes the connection to enter the character. The pattern on the PC board is often gold-plated.

This is a common switch technology used in mass market keyboards today. It is considered very quiet, but purists tend to find it "mushy" because the collapsing dome does not provide as much positive response as a hard closing switch. These are also a good choice for office or consumer environments because they are generally fairly quiet. This switch technology also happens to be most commonly used in handheld controllers, such as those used with home video game consoles.

Dome-switch keyboards are also called direct-switch keyboards.

Capacitive keyboard

In this type of keyboard, pressing the key changes the capacitance of a pattern printed on a PC board. Usually this permits a pulse or pulse train to be sensed. Unlike "dome switch" keyboards, the pattern will be covered by a thin, insulating film. Capacitive keyboards are inexpensive, and resist wear, water, foreign objects and dirt. They are common in PC keyboards.

Mechanical-switch keyboard

Mechanical-switch keyboards use real switches, one under each key. Depending on the construction of the switch, these keyboards have varying responses and travel times. Notable keyboards utilizing this technology are the Apple Extended II, and its modern imitator, the Matias Tactile Pro. These two keyboards use ALPS switches. Cherry Corporation of Germany also makes mechanical switches used in special purpose and high end keyboards. In India, the TVS Gold mechanical keyboard is very popular in spite of the fact that it costs about five times what a membrane keyboard costs. The Matias Tactile Pro is a decent approximation of the Apple Extended II keyboard, however the grade of the plastic is noticeably cheaper. Its construction , besides having decent quality key-switches, is less than par, with flimsy keyboard risers on the bottom of the keyboard and USB ports that are too tight. Although the keyboard has these quality flaws, it`s still better than most available keyboards today, except probably the IBM Model M replacements.

Buckling-spring keyboard

It is a common misconception that the IBM Model M and its derivates are mechanical-switch keyboards. In fact, the Model M uses membrane-sheet switches, much like those found in a dome-switch keyboard. The buckling spring mechanism ( U.S. Patent 4,118,611 ) atop the switch is responsible for the tactile and aural response of the keyboard. This mechanism controls a small hammer that strikes the membrane switch. For more information, see an examination of buckling-spring technology.

In 1993, two years after spawning Lexmark, IBM transferred its keyboard operations to the daughter company. New Model M keyboards continued to be manufactured for IBM by Lexmark until 1996, when Unicomp purchased the keyboard technology. Today, Unicomp manufactures new buckling-spring keyboards and repairs old IBM and Lexmark keyboards. Unfortunately, the later Lexmark-manufactured Model M keyboards are of inferior quality to the original IBM-manufactured Model M. The plastic used is of lower grade (density) and other features such as a detachable heavy duty keyboard cord were replaced by cheap substitutes.

Hall-effect keyboard

Hall effect keyboards use magnets and Hall effect sensors instead of an actual switch. When a key is depressed, it moves a magnet, which is detected by the solid-state sensor. These keyboards are extremely reliable, and are able to accept millions of keystrokes before failing. They are used for ultra-high reliability applications, in locations like nuclear powerplants or aircraft cockpits. They are also sometimes used in industrial environments. These keyboards can be easily made totally waterproof. They also resist large amounts of dust and contaminants. Because a magnet and sensor is required for each key, as well as custom control electronics, they are very expensive.

Laser keyboard

A laser projection device approximately the size of a computer mouse projects the outline of keyboard keys onto a flat surface, such as a table or desk. When the laser is interrupted in the position of a key, a keystroke is registered. This type of keyboard is very portable, and many models have retractable cords and wireless capabilities. However, sudden or accidental disruption of the laser will register unwanted keystrokes. Also, if the laser malfunctions, the whole unit becomes useless, unlike conventional keyboards which can be used even if a variety of parts (such as the keycaps) are removed. This type of keyboard can be cumbersome to use since it is susceptible to errors, even in the course of normal typing, and its complete lack of tactile feedback makes it even less user-friendly than the cheapest membrane keyboards.

Membrane keyboard

Main article: Membrane keyboard

Membrane keyboards are usually flat. They are most often found on appliances like microwave ovens or photocopiers. A common design consists of three layers. The top layer (and the one the user touches) has the labels printed on its front and conductive stripes printed on the back. Under this it has a spacer layer, which holds the front and back layer apart so that they do not normally make electrical contact. The back layer has conductive stripes printed perpendicularly to those of the front layer.

When placed together, the stripes form a grid. When the user pushes down at a particular position, his finger pushes the front layer down through the spacer layer to close a circuit at one of the intersections of the grid. This indicates to the computer or keyboard control processor that a particular button has been pressed.

Membrane keyboards do not generally have much of a "feel", so many machines which use them issue a beep or flash a light when the key is pressed. They are often used in harsh environments where water or leak proofing is desirable. Although used in the early days of the personal computer (on the ZX80, ZX81 and Atari 400), they have been supplanted by the more tactile dome and mechanical switch keyboards. However, membrane keyboards with interchangeable key layouts, such as the IntelliKeys and Discover:board are still commonly used by people with physical, visual, or cognitive disabilities as well as people who require assistive technology to access a computer.

Roll-up keyboard

Some keyboards are designed out of flexible materials that can roll up in a tight (but not too tight) bundle. Normally the external materials are either silicone or PU. It is important to note that although many manufacturers claim that the keyboards are foldable, they cannot be folded without damaging the membrane that holds the circuitry.

Typically they are completely sealed in rubber, making them watertight like membrane keyboards. Like membrane keyboards, they are reported to be very hard to get used to, as there is little tactile feedback.

See Roll-away computer.

Waterproof Keyboards

Waterproof keyboards are designed to prevent the ingress of water from interfering with operation. Membrane keyboards are inherently waterproof due to their absence of areas in which water can enter. Other designs consist of sliding contacts or flexible rubber seals between the deck plate openings and the key stems.

Other parts of PC keyboard

The modern PC keyboard is more than just the switch technology, however. It also includes a control processor and indicator lights to provide feedback to the user about what state the keyboard is in. Depending on the sophistication of the controller`s programming, the keyboard may also offer other special features.

The processor is usually a single chip 8048 microcontroller variant. The keyboard switch matrix is wired to its inputs and it processes the incoming keystrokes and sends the results down a serial cable (the keyboard cord) to a receiver in the main computer box. It also controls the illumination of the " caps lock", " num lock" and " scroll lock" lights.

A common test for whether the computer has crashed is pressing the "caps lock" key. The keyboard sends the key code to the BIOS code running in the main computer; if the main computer is operating, it commands the light to turn on. All the other indicator lights work in a similar way. The BIOS also tracks the shift, alt and control state of the keyboard.

When pressing a keyboard key, the key "bounces" like a ball against its contacts several times before it settles into firm contact. When released, it bounces some more until it reverts to the uncontacted state. If the computer was watching for each pulse, it would see many keystrokes for what the user thought was just one.

To resolve this problem, the processor in a keyboard (or computer) "debounces" the keystrokes, by aggregating them across time to produce one "confirmed" keystroke that (usually) corresponds to what is typically a solid contact. It could be argued that the dome switch technology outlined above owes its popularity to the ability of the processor to accurately debounce the keystrokes. Early membrane keyboards limited typing speed because they had to do significant debouncing. Anyone who ever tried word processing on a ZX81 will recall this.

External links

  • Taking apart a dome-switch keyboard
Retrieved from "http://en.wikipedia.org/wiki/Keyboard_technology" Category: Computer keyboards
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Beware of Spyware - By Nowshade Kabir

 

One day, you suddenly realize that your computer started to work noticeably slower than it used to. You decide to run de-fragmentation of your hard drive and add more virtual memory to the system. No luck! May be, it?s probably some viruses, you reckon turning on your virus scanning software. Even after running the anti-virus program you notice that the problem won?t resolve. Not understanding what?s happening frustrated you pick up the phone. It?s time to call your tech-support. Sounds familiar? You are not alone! Each day, thousands of users are facing similar problems caused by malicious software called Spyware. According to Dell technical support, nowadays 12 percent of their support calls involve problems related to some kinds of Spyware. Microsoft reports that fifty percent of all computer crushes are caused by Spyware, viruses and Trojans.

What is a Spyware?

Spyware ? also named Malware or Adware ? are malicious software programs, which most of the time get installed on your computer without your knowledge. These programs are capable of doing many outrageous, sinister things to your computer such as changing computer settings, tracking your online behavior, monitoring and controlling your computer, recording your keystrokes, displaying unwanted advertisement and reporting needed information back to the person behind it.

The main types of Spyware are:

Key loggers: This type of Spyware copies everything you type to a file and send it to the hacker. The more sophisticated type, which is used for identity theft, copies the information you provide when you are connected to a secure website.

Browser hijacker: It modifies browser settings without your permission. This Spyware is capable of changing your start page, search page, search tool bar and redirect your url to specific pages.

Email redirector: Surreptitiously copies all your incoming and outgoing emails and sends to the hacker.

Dialers: This spyware install themselves to your dial-up settings and dials numbers without your knowledge, often to out of country numbers.

Collectware: The purpose of this Spyware is to track your surfing habit and transmitting the statistical data to the hacker. This information later gets sold to advertisement companies.

Adware: This Spyware downloads all sorts of banner advertisements every time you take some action such as typing a word on your search tool.

Why my antivirus program does not block a Spyware?

Although, Spyware uses same tactics like ?Trojan? virus, technically it is not a virus. A virus is a program written to create trouble or possibly harm your computer system. Viruses are capable of replicate, evolve and cause severe damages to your computer files, registry or even hardware. Spyware, on the other hand, does not harm your computer intentionally. Any nuisance like system slow down is the collateral damage, which occurs while the Spyware serves its mission of monitoring your activities and making unwanted changes to your user experience.

People rarely read the fine prints of the user agreements while downloading a file, a program, a game or other free stuffs from the Internet. Unethical sites use this to their advantage and add tiny Spyware with the file you are downloading.

The anti-virus programs can not be sure, whether this program is installed deliberately by you or it?s a malicious Spyware. This makes identifying and blocking a Spyware difficult for an Anti-virus program. However, things are started to change! Major anti-virus companies are planning to integrate anti-spyware programs to their existing products very soon.

How did I get infected with a Spyware?

There are numerous ways how you might end up with having a Spyware on your system.

- When you download and install programs, games, smilies, pictures, screensavers from dubious sites, there is a big chance that you might install a sneaky Spyware along the way.

- Some websites and pop-up windows try to download and install Spyware while you are there. According a recent analysis of sex-based websites, up to 80 percent of these sites are now being used to upload Spyware, worms and Trojans to unsuspecting visitors.

- Some add-ons to you browser that is supposed to enhance your browser experience may secretively install Spyware.

- The most cynical method of infecting you with Spyware is when you receive a sudden pop-up ad, which claims that your computer is contaminated and you have to run certain program to cure your system. If you are credulous enough to run this program, it just installs a Spyware instead of eliminating any.

How to fight back?

If you carefully follow the instructions outlined below, your chances of getting infected with Spyware are pretty slim.

Update your Windows

Allow your version of Windows to update it automatically. Ensure that you have all the latest security patches installed.

Use Firefox as your default browser

Since Internet Explorer is the main target for many Spyware, you will be better of with Mozilla Firefox. Moreover, it is a better browser than IE in many aspects.

Be extremely careful with your downloads

Try not to download anything from a unknown site. If you still feel like getting a shareware or freeware program check it out on one of these online Spyware database. Spychecker (http://www.spychecker.com/) is one such service, and Camtech 2000`s Spy Chaser (http://camtech2000.net/Pages/SpyChaser.html) is a nifty downloadable database of nearly 1000 spyware-infested programs.

Use an Anti-Spyware application

Download and install one of the following anti-spyware programs:

Ad-aware (http://www.lavasoftusa.com/software/adaware/), Spybot (http://www.safer-networking.org/en/spybotsd/index.html) and Microsoft AntiSpyware. Although, Microsoft?s Anti-Spyware

(http://www.microsoft.com/athome/security/spyware/software/default.mspx) is still at beta stage, I am using it and very happy with its performance.

Get a Firewall

If you are using Windows XP with Service Pack 2, you are probably fine! In other cases, if your computer is connected to the Internet directly you should get a firewall and install it. Zone alarm

(http://www.zonelabs.com/store/content/home.jsp) is a great firewall you can download for free.

A recently conducted survey of the Top Network Security threats in 2005 reveals that two-thirds of IT managers and administrators believe that Spyware will be the number one threat to network security. So don?t take any chance! Make sure that you are protected!


Nowshade Kabir is the founder, primary developer and present CEO of Rusbiz.com. A Ph. D. in Information Technology, he has wide experience in Business Consulting, International Trade and Web Marketing. Rusbiz is a Global B2B Emarketplace with solutions to start and run online business. You can contact him at mailto:nowshade[at]rusbiz.com http://ezine.rusbiz.com

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