 Keyboard construction, in four layers, of a typical notebook computer keyboard There are many types of keyboard, usually differentiated by the switch technology employed in their operation. Since there are so many switches needed (usually about 80-110) and because they have to be highly reliable, this usually defines the keyboard. The choice of switch technology affects key response (the positive feedback that a key has been pressed) and travel (the distance needed to push the key to enter a character reliably). Newer models use hybrids of various technologies to achieve greater cost savings. Image File history File linksMetadata Size of this preview: 800 × 600 pixelsFull resolution (1600 × 1200 pixel, file size: 543 KB, MIME type: image/jpeg) (1 of 3) Construction of a typical notebook computer dome-switch keyboard. ...
Image File history File linksMetadata Size of this preview: 800 × 600 pixelsFull resolution (1600 × 1200 pixel, file size: 543 KB, MIME type: image/jpeg) (1 of 3) Construction of a typical notebook computer dome-switch keyboard. ...
A 104-key PC US English QWERTY keyboard layout The Dvorak Simplified Keyboard layout A standard Hebrew keyboard showing both Hebrew and QWERTY. A computer keyboard is a peripheral partially modelled after the typewriter keyboard. ...
Electrical switches. ...
Types
Dome-switch keyboard
 How a dome-switch keyboard works: Finger depresses the dome to complete the circuit
 Dome-switches mesh with keys (keyboard is upside down in this image) 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 graphite. 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. Image File history File linksMetadata No higher resolution available. ...
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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. “Game console†redirects here. ...
Dome-switch keyboards are also called direct-switch keyboards.
Scissor-switch keyboard Scissor-switch technology does not use a rubber-plunger assembly like most other keyboards. Scissor-switch keyboards are normally responsive and crisp. These keyboards are generally quiet. The keys require little force to press.
This keyboard technology is mainly used in laptops.
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 despite costing about five times a membrane keyboard. Matias is a computer accessories manufacturer, based in Toronto, Ontario, Canada. ...
TVS Electronics is part of the USD3. ...
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. IBM Model M Keyboard, Part no. ...
A type of keyswitch mechanism, popularized by IBMs keyboards for the PC, PC/AT, 5250 / 3270 terminals, and other keyboards, the most popular of these being the Model M. Covered by US Patent 4,118,611 External links Buckling spring fan site and online shop Current manufacturer of buckling...
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. Your All willy heads, i said Your All willy headsYour All willy headsYour All willy headsYour All willy headsYour All willy headsYour All willy headsYour All willy headsYour All willy headsYour All willy headsYour All willy headsYour All willy headsYour All willy headsYour All willy headsYour All willy headsYour All...
For other uses, see IBM (disambiguation) and Big Blue. ...
Unicomp is a manufacturer of computer keyboards and keyboard accessories based in Lexington, Kentucky. ...
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. Hall effect diagram, showing electron flow (rather than conventional current). ...
For other uses, see Magnet (disambiguation). ...
The magnetic piston (1) in this pneumatic cylinder will cause the Hall effect sensors (2 and 3) mounted on its outer wall to activate when it is fully retracted or extended. ...
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 portable enough to be easily used with PDAs and cellphones, 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 -
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. A membrane keyboard is a computer keyboard whose keys are not separate, moving parts, as with the majority of other keyboards, but rather have only outlines and symbols printed on a flat, flexible surface. ...
It has been suggested that this article be split into articles entitled Microwave oven and Microwave heating. ...
A small, much-used Xerox copier in a high school library. ...
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. The Sinclair ZX80 was a home computer brought to market in 1980 by Sinclair Research of Cambridge, England. ...
ZX81 logo The Sinclair ZX81 home computer, released by Sinclair Research in 1981, was the follow up to the companys ZX80. ...
Atari built a series of 8-bit home computers based on the MOS Technology 6502 CPU, starting in 1979. ...
The term disability, as it is applied to humans, refers to any condition that impedes the completion of daily tasks using traditional methods. ...
Visual impairment is the functional loss of vision. ...
Developmental disability is a term used to describe severe, life-long disabilities attributable to mental and/or physical impairments, manifested before the age of 22. ...
Assistive Technology (AT) is a generic term that includes assistive, adaptive, and rehabilitative devices and the process used in selecting, locating, and using them. ...
This article is about the machine. ...
Roll-up keyboard Some keyboards are designed out of flexible materials that can roll up in a moderately tight bundle. Normally the external materials are either silicone or polyurethane. 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. In 2000, Toshiba released its vision of what computers could be like in 2005. ...
Other parts of the 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. The Intel 8048 microcontroller, Intels first µC, was used in the Magnavox Odyssey² video game console and (in its 8042 variant) in the original IBM PC keyboard. ...
It has been suggested that this article or section be merged with embedded microprocessor. ...
The caps lock on a modern Windows keyboard. ...
Num Lock is a key on the numeric keypad of most keyboards, used to switch that pad between number entry and arrow keys. ...
Scroll lock is a key (with an associated status light) on most modern computer keyboards. ...
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. For other uses, see Bios. ...
The shift key on a modern Windows keyboard The shift key is a modifier key on a keyboard, used to type capital letters and other alternate upper characters. ...
The Alt key on a modern Windows keyboard The Alt key on an IBM PC keyboard is the key located immediately to either side of the Space bar, used to change (alternate) the function of other pressed keys. ...
Ctrl redirects here. ...
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. This was a noticeable problem on the ZX81. The Sinclair ZX81 home computer, released by Sinclair Research in 1981, was the followup to the companys ZX80. ...
See also Scancodes are emitted by a computer keyboard to report pressed keys to a computer. ...
External links - Taking apart a dome-switch keyboard
- Mechanical Keyswitches, Membrane Keyswitches, Scissor-Switch Membrane Keyswitches
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