![Keyboard Construction](https://upload.wikimedia.org/wikipedia/commons/9/97/Keyboard_Construction.JPG)
The technology of computer keyboards includes many elements. Among the more important of these is the
switch
In electrical engineering, a switch is an electrical component that can disconnect or connect the conducting path in an electrical circuit, interrupting the electric current or diverting it from one conductor to another. The most common type of ...
technology that they use. Computer alphanumeric keyboards typically have 80 to 110 durable switches, generally one for each key. The choice of switch technology affects key response (the positive feedback that a key has been pressed) and pre-travel (the distance needed to push the key to enter a character reliably).
Virtual keyboards
A virtual keyboard is a software component that allows the input of characters without the need for physical keys. The interaction with the virtual keyboard happens mostly via a touchscreen interface, but can also take place in a different form ...
on
touch screens
A touchscreen or touch screen is the assembly of both an input ('touch panel') and output ('display') device. The touch panel is normally layered on the top of an electronic visual display of an information processing system. The display is often ...
have no physical switches and provide audio and
haptic feedback instead. Some newer keyboard models use hybrids of various technologies to achieve greater cost savings or better
ergonomics
Human factors and ergonomics (commonly referred to as human factors) is the application of psychological and physiological principles to the engineering and design of products, processes, and systems. Four primary goals of human factors learnin ...
.
The modern keyboard also includes a control processor and indicator lights to provide feedback to the user (and to the
central processor
A central processing unit (CPU), also called a central processor, main processor or just processor, is the electronic circuitry that executes instructions comprising a computer program. The CPU performs basic arithmetic, logic, controlling, ...
) about what state the keyboard is in.
Plug and play
In computing, a plug and play (PnP) device or computer bus is one with a specification that facilitates the recognition of a hardware component in a system without the need for physical device configuration or user intervention in resolving resou ...
technology means that its 'out of the box'
layout
Layout may refer to:
* Page layout, the arrangement of visual elements on a page
** Comprehensive layout (comp), a proposed page layout presented by a designer to their client
* Layout (computing), the process of calculating the position of obje ...
can be notified to the system, making the keyboard immediately ready to use without need for further configuration unless the user so desires.
Types
Membrane keyboard
![Atari 400 keyboard](https://upload.wikimedia.org/wikipedia/commons/7/7f/Atari_400_keyboard.jpg)
There are two types of membrane-based keyboards, flat-panel membrane keyboards and full-travel membrane keyboards:
Flat-panel membrane keyboards are most often found on appliances like
microwave oven
A microwave oven (commonly referred to as a microwave) is an electric oven that heats and cooks food by exposing it to electromagnetic radiation in the microwave frequency range. This induces polar molecules in the food to rotate and produce t ...
s or
photocopier
A photocopier (also called copier or copy machine, and formerly Xerox machine, the generic trademark) is a machine that makes copies of documents and other visual images onto paper or plastic film quickly and cheaply. Most modern photocopiers u ...
s. A common design consists of three layers. The top layer 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, their 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.
Generally, flat-panel membrane keyboards do not produce a noticeable physical feedback. Therefore, devices using these 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
A personal computer (PC) is a multi-purpose microcomputer whose size, capabilities, and price make it feasible for individual use. Personal computers are intended to be operated directly by an end user, rather than by a computer expert or tec ...
(on the
Sinclair ZX80
The Sinclair ZX80 is a home computer launched on 29 January 1980 by Science of Cambridge Ltd. (later to be better known as Sinclair Research). It is notable for being one of the first computers available in the United Kingdom for less than a h ...
,
ZX81
The ZX81 is a home computer that was produced by Sinclair Research and manufactured in Dundee, Scotland, by Timex Corporation. It was launched in the United Kingdom in March 1981 as the successor to Sinclair's ZX80 and designed to be a low-cost ...
and
Atari 400
The Atari 8-bit family is a series of 8-bit home computers introduced by Atari, Inc. in 1979 as the Atari 400 and Atari 800. The series was successively upgraded to Atari 1200XL , Atari 600XL, Atari 800XL, Atari 65XE, Atari 130XE, Atari 800XE ...
), they have been supplanted by the more tactile dome and mechanical switch keyboards.
Full-travel membrane-based keyboards are the most common computer keyboards today. They have one-piece plastic keytop/switch plungers which press down on a membrane to actuate a contact in an electrical switch matrix.
Dome-switch keyboard
![Membrane keyboard](https://upload.wikimedia.org/wikipedia/commons/6/6e/Membrane_keyboard.jpg)
Dome-switch keyboards are a hybrid of
flat-panel membrane and mechanical-switch keyboards. They bring two circuit board traces together under a
rubber
Rubber, also called India rubber, latex, Amazonian rubber, ''caucho'', or ''caoutchouc'', as initially produced, consists of polymers of the organic compound isoprene, with minor impurities of other organic compounds. Thailand, Malaysia, and ...
or
silicone
A silicone or polysiloxane is a polymer made up of siloxane (−R2Si−O−SiR2−, where R = organic group). They are typically colorless oils or rubber-like substances. Silicones are used in sealants, adhesives, lubricants, medicine, cooking ...
keypad using either metal "dome" switches or
polyurethane
Polyurethane (; often abbreviated PUR and PU) refers to a class of polymers composed of organic chemistry, organic units joined by carbamate (urethane) links. In contrast to other common polymers such as polyethylene and polystyrene, polyurethan ...
formed domes. The metal dome switches are formed pieces of stainless steel that, when compressed, give the user a crisp, positive tactile feedback. These metal types of dome switches are very common, are usually reliable to over 5 million cycles, and can be plated in either nickel, silver or gold. The rubber dome switches, most commonly referred to as polydomes, are formed polyurethane domes where the inside bubble is coated in graphite. While polydomes are typically cheaper than metal domes, they lack the crisp snap of the metal domes, and usually have a lower life specification. Polydomes are considered very quiet, but purists tend to find them "mushy" because the collapsing dome does not provide as much positive response as metal domes. For either metal or polydomes, when a key is pressed, it collapses the dome, which connects the two circuit traces and completes the connection to enter the character. The pattern on the PC board is often gold-plated.
Both are common switch technologies used in mass market keyboards today. This type of switch technology happens to be most commonly used in handheld controllers, mobile phones, automotive, consumer electronics and medical devices. Dome-switch keyboards are also called direct-switch keyboards.
Scissor-switch keyboard
![Scissor switch mechanism](https://upload.wikimedia.org/wikipedia/commons/e/e0/Scissor_switch_mechanism.svg)
A special case of the computer keyboard dome-switch is the scissor-switch. The keys are attached to the keyboard via two plastic pieces that interlock in a "scissor"-like fashion, and snap to the keyboard and the key. It still uses rubber domes, but a special plastic
'scissors' mechanism links the
keycap
A keycap is a small cover of plastic, metal, or other material placed over the keyswitch of a computer keyboard. Keycaps are often illustrated to indicate the key function or alphanumeric
Alphanumericals or alphanumeric characters are a co ...
to a plunger that depresses the rubber dome with a much shorter travel than the typical rubber dome keyboard. Typically scissor-switch keyboards also employ 3-layer membranes as the electrical component of the switch. They also usually have a shorter total key travel distance (2 mm instead of 3.5–4 mm for standard dome-switch keyswitches). This type of keyswitch is often found on the built-in keyboards on laptops and keyboards marketed as 'low-profile'. These keyboards are generally quiet and the keys require little force to press.
Scissor-switch keyboards are typically slightly more expensive. They are harder to clean (due to the limited movement of the keys and their multiple attachment points) but also less likely to get debris in them as the gaps between the keys are often smaller (as there is no need for extra room to allow for the 'wiggle' in the key, as typically found on a membrane keyboard).
Capacitive keyboard
In this type of keyboard, pressing a key changes the capacitance of a pattern of capacitor pads. The pattern consists of two D-shaped capacitor pads for each switch, printed on a
printed circuit board
A printed circuit board (PCB; also printed wiring board or PWB) is a medium used in Electrical engineering, electrical and electronic engineering to connect electronic components to one another in a controlled manner. It takes the form of a L ...
(PCB) and covered by a thin, insulating film of
soldermask
Solder mask, solder stop mask or solder resist is a thin lacquer-like layer of polymer that is usually applied to the copper traces of a printed circuit board (PCB) for protection against oxidation and to prevent solder bridges from forming ...
which acts as a
dielectric
In electromagnetism, a dielectric (or dielectric medium) is an electrical insulator that can be polarised by an applied electric field. When a dielectric material is placed in an electric field, electric charges do not flow through the mate ...
.
Despite the sophistication of the concept, the mechanism of capacitive switching is physically simple. The movable part ends with a flat foam element about the size of an
aspirin tablet, finished with aluminum foil. Opposite the switch is a PCB with the capacitor pads. When the key is pressed, the foil tightly clings to the surface of the PCB, forming a
daisy chain
Daisy chain may refer to:
* Daisy chain, a garland created from daisy flowers
* Daisy chain (climbing), a type of strap
* Daisy chain (electrical engineering), a wiring scheme
* Daisy chain (fishing), a type of fishing lure
* Daisy chain (knot), ...
of two capacitors between
contact pad
Contact pads or bond pads are designated surface areas of a printed circuit board (PCB) or die of an integrated circuit.
Possibilities to contact to pads include soldering, wirebonding, flip chip
Flip chip, also known as controlled collapse ...
s and itself separated with thin soldermask, and thus "shorting" the
contact pad
Contact pads or bond pads are designated surface areas of a printed circuit board (PCB) or die of an integrated circuit.
Possibilities to contact to pads include soldering, wirebonding, flip chip
Flip chip, also known as controlled collapse ...
s with an easily detectable drop of
capacitive reactance
In electrical circuits, reactance is the opposition presented to alternating current by inductance or capacitance. Greater reactance gives smaller current for the same applied voltage. Reactance is similar to resistance in this respect, but doe ...
between them. Usually this permits a pulse or pulse train to be sensed. Because the switch does not have an actual electrical contact, there is no
debouncing
In electrical engineering, a switch is an electrical component that can disconnect or connect the conducting path in an electrical circuit, interrupting the electric current or diverting it from one conductor to another. The most common typ ...
necessary. The keys do not need to be fully pressed to be actuated, which enables some people to type faster. The sensor tells enough about the position of the key to allow the user to adjust the actuation point (key sensitivity). This adjustment can be done with the help of the bundled software and individually for each key, if so implemented.
The IBM
Model F keyboard
The Model F was a series of computer keyboards produced mainly from 1981–1985 and in reduced volume until 1994 by IBM and later Lexmark. Its mechanical-key design consisted of a buckling spring over a capacitive PCB, similar to the later Mod ...
is mechanical-key design consisted of a buckling spring over a capacitive PCB, similarly to the later Model M keyboard that used a membrane in place of the PCB.
The
Topre Corporation design for key switches uses a spring below a rubber dome. The dome provides most of the force that keeps the key from being pressed, similar to a membrane keyboard, while the spring helps with the capacitive action.
Mechanical-switch keyboard
![RK68](https://upload.wikimedia.org/wikipedia/commons/2/25/RK68.jpg)
Every key on a mechanical-switch keyboard contains a complete switch underneath. Each switch is composed of a housing, a spring, and a stem, and sometimes other parts such as a separate tactile leaf or a clickbar.
Switches
In electrical engineering, a switch is an electrical component that can disconnect or connect the conducting path in an electrical circuit, interrupting the electric current or diverting it from one conductor to another. The most common type of ...
come in three variants: "linear" with consistent resistance, "tactile" with a non-audible bump, and "clicky" with both a bump and an audible click. Depending on the resistance of the spring, the key requires different amounts of pressure to actuate and to bottom out. The shape of the stem as well as the design of the switch housing varies the actuation distance and travel distance of the switch. The sound can be altered by the material of the plate, case, lubrication, the keycap profile, and even modifying the individual switch. These modifications, or "mods" include applying
lubricant
A lubricant (sometimes shortened to lube) is a substance that helps to reduce friction between surfaces in mutual contact, which ultimately reduces the heat generated when the surfaces move. It may also have the function of transmitting forces, t ...
to reduce friction inside the switch itself, inserting "switch films" to reduce wobble, swapping out the spring inside to modify the resistance of the switch itself and many more. Mechanical keyboards allow for the removal and replacement of keycaps with a common stem type.
Alongside the mechanical keyboard switch is the stabilizer, which supports longer keys such as the "spacebar", "enter", "backspace", and "shift" keys. Although these are not as diverse as switches, they come in different sizes. These different sizes are designed for keyboards that are longer than normal. Similar to a mechanical keyboard switch, the stabilizer can be modified to alter the sound and feel of these certain keys. Lubricant can be used to reduce the rattle of the metal wire that makes up a stabilizer. Furthermore, implementing padding in the "housing" of the stabilizer will lessen rattle and improve acoustics.
Mechanical keyboards typically have a longer lifespan than membrane or dome-switch keyboards.
A major producer of mechanical switches is
Cherry
A cherry is the fruit of many plants of the genus ''Prunus'', and is a fleshy drupe (stone fruit).
Commercial cherries are obtained from cultivars of several species, such as the sweet ''Prunus avium'' and the sour ''Prunus cerasus''. The nam ...
, who has manufactured the MX family of switches since the 1980s. Cherry's color-coding system of categorizing switches has been imitated by other mechanical switch manufacturers, such as Gateron and Kailh amongst many others.
Hot-swappable keyboard
Hot-swappable
Hot swapping is the replacement or addition of components to a Computer, computer system without stopping, shutdown (computing), shutting down, or Reboot, rebooting the system; hot plugging describes the addition of components only. Components ...
keyboards are keyboards where switches can be pulled out and replaced rather than requiring the typical
solder
Solder (; NA: ) is a fusible metal alloy used to create a permanent bond between metal workpieces. Solder is melted in order to wet the parts of the joint, where it adheres to and connects the pieces after cooling. Metals or alloys suitable ...
connection. Instead of the ''switch'' being soldered to the keyboard's
PCB
PCB may refer to:
Science and technology
* Polychlorinated biphenyl, an organic chlorine compound, now recognized as an environmental toxin and classified as a persistent organic pollutant
* Printed circuit board, a board used in electronics
* ...
, hot-swap ''sockets'' are instead soldered on. They are mostly used by keyboard enthusiasts that build custom keyboards, and have recently begun being adopted by larger companies on production keyboards. Hot-swap sockets typically cost anywhere from $10–25 USD to fill a complete board and can allow users to try a variety of different switches without having the tools or knowledge required to solder electronics.
Buckling-spring keyboard
![Bucklingspring1-o](https://upload.wikimedia.org/wikipedia/commons/9/90/Bucklingspring1-o.svg)
Many typists prefer
buckling spring
A buckling spring is a type of keyswitch mechanism, popularized by IBM's keyboards for the PC, PC/AT, 5250/3270 terminals, PS/2, and other systems. It was used by IBM's Model F keyboards (for instance the AT keyboard), and the more common M ...
keyboards. The
buckling spring
A buckling spring is a type of keyswitch mechanism, popularized by IBM's keyboards for the PC, PC/AT, 5250/3270 terminals, PS/2, and other systems. It was used by IBM's Model F keyboards (for instance the AT keyboard), and the more common M ...
mechanism (expired ) atop the switch is responsible for the tactile and aural response of the keyboard. This mechanism controls a small hammer that strikes a capacitive or membrane switch.
In 1993, two years after spawning
Lexmark
Lexmark International, Inc. is a privately held American company that manufactures laser printers and imaging products. The company is headquartered in Lexington, Kentucky. Since 2016 it has been jointly owned by a consortium of three multination ...
,
IBM transferred its keyboard operations to the daughter company. New
Model M keyboard
Model M designates a group of computer keyboards designed and manufactured by IBM starting in 1985, and later by Lexmark International, Maxi Switch, and Unicomp. The keyboard's many variations have their own distinct characteristics, with ...
s continued to be manufactured for IBM by Lexmark until 1996, when
Unicomp
Unicomp is a manufacturer of computer keyboards and keyboard accessories, based in Lexington, Kentucky, United States.
History
In 1996, Lexmark International was prepared to shut their Lexington keyboard factory where they produced Model M buck ...
was established and purchased the keyboard patents and tooling equipment to continue their production.
IBM continued to make Model M's in their Scotland factory until 1999.
Hall-effect keyboard
Hall effect
The Hall effect is the production of a voltage difference (the Hall voltage) across an electrical conductor that is transverse to an electric current in the conductor and to an applied magnetic field perpendicular to the current. It was disco ...
keyboards use
magnet
A magnet is a material or object that produces a magnetic field. This magnetic field is invisible but is responsible for the most notable property of a magnet: a force that pulls on other ferromagnetic materials, such as iron, steel, nickel, ...
s and
Hall effect sensor
A Hall effect sensor (or simply Hall sensor) is a type of sensor which detects the presence and magnitude of a magnetic field using the Hall effect. The output voltage of a Hall sensor is directly proportional to the strength of the field. ...
s instead of switches with mechanical contacts. When a key is depressed, it moves a magnet that is detected by a solid-state sensor. Because they require no physical contact for actuation, Hall-effect keyboards are extremely reliable and can accept millions of keystrokes before failing. They are used for ultra-high reliability applications such as nuclear power plants, aircraft cockpits, and critical industrial environments. They can easily be made totally waterproof, and can resist large amounts of dust and contaminants. Because a magnet and sensor are required for each key, as well as custom control electronics, they are expensive to manufacture.
Laser projection 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. 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 frustrating 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 lowest quality membrane keyboards.
Roll-up keyboard
![Foldable keyboard](https://upload.wikimedia.org/wikipedia/commons/2/2c/Foldable_keyboard.jpg)
Keyboards made of flexible silicone or polyurethane materials can roll up in a bundle. Tightly folding the keyboard may damage the internal membrane circuits. When they are completely sealed in rubber, they are water resistant. Roll-up keyboards provide relatively little tactile feedback, and silicone will tend to attract dirt, dust, and hair.
Optical keyboard technology
Also known as photo-optical keyboard, light responsive keyboard, photo-electric keyboard, and optical key actuation detection technology.
Optical keyboard technology was introduced in 1962 by Harley E. Kelchner for use in a typewriter machine with the purpose of reducing the noise generating by actuating the typewriter keys.
An optical keyboard technology utilizes
light-emitting devices and
photo sensors to optically detect actuated keys. Most commonly the emitters and sensors are located at the perimeter, mounted on a small
PCB
PCB may refer to:
Science and technology
* Polychlorinated biphenyl, an organic chlorine compound, now recognized as an environmental toxin and classified as a persistent organic pollutant
* Printed circuit board, a board used in electronics
* ...
. The
light
Light or visible light is electromagnetic radiation that can be perceived by the human eye. Visible light is usually defined as having wavelengths in the range of 400–700 nanometres (nm), corresponding to frequencies of 750–420 tera ...
is directed from side to side of the keyboard interior, and it can only be blocked by the actuated keys. Most optical keyboards require at least two beams (most commonly a vertical beam and a horizontal beam) to determine the actuated key. Some optical keyboards use a special key structure that blocks the light in a certain pattern, allowing only one beam per row of keys (most commonly a horizontal beam).
The mechanism of the optical keyboard is very simple – a light beam is sent from the emitter to the receiving sensor, and the actuated key blocks,
reflects,
refracts
In physics, refraction is the redirection of a wave as it passes from one transmission medium, medium to another. The redirection can be caused by the wave's change in speed or by a change in the medium. Refraction of light is the most common ...
or otherwise interacts with the beam, resulting in an identified key.
Some earlier optical keyboards were limited in their structure and required special casing to block external light, no multi-key functionality was supported and the design was very limited to a thick rectangular case.
The advantages of optical keyboard technology are that it offers a real waterproof keyboard, resilient to dust and liquids; and it uses about 20% PCB volume, compared with membrane or dome switch keyboards, significantly reducing
electronic waste
Electronic waste or e-waste describes discarded electrical or electronic devices. Used electronics which are destined for refurbishment, reuse, resale, salvage recycling through material recovery, or disposal are also considered e-waste. Informa ...
.
Additional advantages of optical keyboard technology over other keyboard technologies such as Hall effect, laser, roll-up, and transparent keyboards lie in cost (Hall effect keyboard) and feel – optical keyboard technology does not require different key mechanisms, and the tactile feel of typing has remained the same for over 60 years.
The specialist
DataHand
The DataHand is an unconventional computer keyboard introduced by 1990, by DataHand Systems, Inc, designed to be operated without any wrist motion or finger extension.
History
Datahand Systems, Inc. was founded in 1985. It was invented by Dale ...
keyboard uses optical technology to sense keypresses with a single light beam and sensor per key. The keys are held in their rest position by
magnet
A magnet is a material or object that produces a magnetic field. This magnetic field is invisible but is responsible for the most notable property of a magnet: a force that pulls on other ferromagnetic materials, such as iron, steel, nickel, ...
s; when the magnetic force is overcome to press a key, the optical path is unblocked and the keypress is registered.
Debouncing
![Bouncy Switch](https://upload.wikimedia.org/wikipedia/commons/a/ac/Bouncy_Switch.png)
When a key is pressed, it oscillates (''bounces'') against its contacts several times before settling. When released, it oscillates again until it comes to rest. Although it happens on a scale too small to be visible to the naked eye, it can be enough to register multiple keystrokes.
To resolve this, the processor in a keyboard ''debounces'' the keystrokes, by averaging the signal over time to produce one "confirmed" keystroke that (usually) corresponds to a single press or release. Early membrane keyboards had limited typing speed because they had to do significant debouncing. This was a noticeable problem on the
ZX81
The ZX81 is a home computer that was produced by Sinclair Research and manufactured in Dundee, Scotland, by Timex Corporation. It was launched in the United Kingdom in March 1981 as the successor to Sinclair's ZX80 and designed to be a low-cost ...
.
Keycaps
Keycap
A keycap is a small cover of plastic, metal, or other material placed over the keyswitch of a computer keyboard. Keycaps are often illustrated to indicate the key function or alphanumeric
Alphanumericals or alphanumeric characters are a co ...
s are used on full-travel keyboards. While modern keycaps are typically surface-printed, they can also be
double-shot molded, laser printed, sublimation printed, engraved, or they can be made of transparent material with printed paper inserts.
There are also keycaps which are thin shells that are placed over key bases. These were used on IBM PC keyboards.
Other parts
The modern PC keyboard 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
The MCS-48 microcontroller series, Intel's first microcontroller, was originally released in 1976. Its first members were 8048, 8035 and 8748. The 8048 is probably the most prominent member of the family. Initially, this family was produced us ...
microcontroller
A microcontroller (MCU for ''microcontroller unit'', often also MC, UC, or μC) is a small computer on a single VLSI integrated circuit (IC) chip. A microcontroller contains one or more CPUs (processor cores) along with memory and programmable i ...
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
keyboard driver 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 keyboard driver also tracks the
shift,
alt
Alt or ALT may refer to:
Abbreviations for words
* Alt account, an alternative online identity also known as a sock puppet account
* Alternate character, in online gaming
* Alternate route, type of highway designation
* Alternating group, mathema ...
and
control
Control may refer to:
Basic meanings Economics and business
* Control (management), an element of management
* Control, an element of management accounting
* Comptroller (or controller), a senior financial officer in an organization
* Controllin ...
state of the keyboard.
Keyboard switch matrix
![Klavye_20](https://upload.wikimedia.org/wikipedia/commons/d/dc/Klavye_20.JPG)
The keyboard switch matrix is often drawn with horizontal wires and vertical wires in a grid which is called a
matrix circuit. It has a switch at some or all intersections, much like a
multiplexed display
Multiplexed displays are electronic display devices where the entire display is not driven at one time.
Instead, sub-units of the display (typically, rows or columns for a dot matrix display or individual characters for a character oriented dis ...
.
Ghost keys
Almost all keyboards have only the ''switch'' (but no diode) at each intersection, which causes "ghost keys" and "key jamming" when multiple keys are pressed (
rollover). Certain, often more expensive, keyboards have a diode between each intersection, allowing the keyboard microcontroller to accurately sense any number of simultaneous keys being pressed, without generating erroneous ghost keys.
Alternative text-entering methods
Optical character recognition
Optical character recognition or optical character reader (OCR) is the electronic or mechanical conversion of images of typed, handwritten or printed text into machine-encoded text, whether from a scanned document, a photo of a document, a scen ...
(OCR) is preferable to rekeying for converting existing text that is already written down but not in machine-readable format (for example, a
Linotype-composed book from the 1940s). In other words, to convert the text from an image to editable text (that is, a string of character codes), a person could re-type it, or a computer could look at the image and deduce what each character is. OCR technology has already reached an impressive state (for example,
Google Book Search
Google Books (previously known as Google Book Search, Google Print, and by its code-name Project Ocean) is a service from Google Inc. that searches the full text of books and magazines that Google has scanned, converted to text using optical c ...
) and promises more for the future.
Speech recognition
Speech recognition is an interdisciplinary subfield of computer science and computational linguistics that develops methodologies and technologies that enable the recognition and translation of spoken language into text by computers with the m ...
converts speech into machine-readable text (that is, a string of character codes). This technology has also reached an advanced state and is implemented in
various software products. For certain uses (e.g., transcription of medical or legal dictation; journalism; writing essays or novels) speech recognition is starting to replace the keyboard. However, the lack of privacy when issuing voice commands and dictation makes this kind of input unsuitable for many environments.
Pointing device
A pointing device is a human interface device that allows a user to input spatial (i.e., continuous and multi-dimensional) data to a computer. CAD systems and graphical user interfaces (GUI) allow the user to control and provide data to t ...
s can be used to enter text or characters in contexts where using a physical keyboard would be inappropriate or impossible. These accessories typically present characters on a display, in a layout that provides fast access to the more frequently used characters or character combinations. Popular examples of this kind of input are
Graffiti
Graffiti (plural; singular ''graffiti'' or ''graffito'', the latter rarely used except in archeology) is art that is written, painted or drawn on a wall or other surface, usually without permission and within public view. Graffiti ranges from s ...
,
Dasher and on-screen
virtual keyboard
A virtual keyboard is a software component that allows the Input device, input of characters without the need for physical keys. The interaction with the virtual Computer keyboard, keyboard happens mostly via a touchscreen interface, but can also ...
s.
Other issues
Keystroke logging
Unencrypted
Bluetooth
Bluetooth is a short-range wireless technology standard that is used for exchanging data between fixed and mobile devices over short distances and building personal area networks (PANs). In the most widely used mode, transmission power is limi ...
keyboards are known to be vulnerable to signal theft for keylogging by other Bluetooth devices in range.
Microsoft
Microsoft Corporation is an American multinational technology corporation producing computer software, consumer electronics, personal computers, and related services headquartered at the Microsoft Redmond campus located in Redmond, Washing ...
wireless keyboards 2011 and earlier are documented to have this vulnerability.
Keystroke logging
Keystroke logging, often referred to as keylogging or keyboard capturing, is the action of recording (logging) the keys struck on a keyboard, typically covertly, so that a person using the keyboard is unaware that their actions are being monitored ...
(often called keylogging) is a method of capturing and recording user keystrokes. While it can be used legally to measure employee activity, or by law enforcement agencies to investigate suspicious activities, it is also used by
hackers
A hacker is a person skilled in information technology who uses their technical knowledge to achieve a goal or overcome an obstacle, within a computerized system by non-standard means. Though the term ''hacker'' has become associated in popu ...
for illegal or malicious acts. Hackers use keyloggers to obtain passwords or encryption keys.
Keystroke logging can be achieved by both hardware and software means. Hardware key loggers are attached to the keyboard cable or installed inside standard keyboards. Software keyloggers work on the target computer's operating system and gain unauthorized access to the hardware, hook into the keyboard with functions provided by the OS, or use remote access software to transmit recorded data out of the target computer to a remote location. Some hackers also use wireless keylogger sniffers to collect packets of data being transferred from a wireless keyboard and its receiver, and then they crack the encryption key being used to secure wireless communications between the two devices.
Anti-spyware
Spyware (a portmanteau for spying software) is software with malicious behaviour that aims to gather information about a person or organization and send it to another entity in a way that harms the user—for example, by violating their priva ...
applications are able to detect many keyloggers and remove them. Responsible vendors of monitoring software support detection by anti-spyware programs, thus preventing abuse of the software. Enabling a
firewall
Firewall may refer to:
* Firewall (computing), a technological barrier designed to prevent unauthorized or unwanted communications between computer networks or hosts
* Firewall (construction), a barrier inside a building, designed to limit the spre ...
does not stop keyloggers per se, but can possibly prevent transmission of the logged material over the net if properly configured.
Network monitors (also known as reverse-firewalls) can be used to alert the user whenever an application attempts to make a network connection. This gives the user the chance to prevent the keylogger from "
phoning home
In computing, phoning home is a term often used to refer to the behavior of security systems that report network location, username, or other such data to another computer.
Phoning home may be useful for the proprietor in tracking a missing or st ...
" with his or her typed information. Automatic form-filling programs can prevent keylogging entirely by not using the keyboard at all. Most keyloggers can be fooled by alternating between typing the login credentials and typing characters somewhere else in the focus window.
Keyboards are also known to emit electromagnetic signatures that can be detected using special spying equipment to reconstruct the keys pressed on the keyboard. Neal O'Farrell, executive director of the Identity Theft Council, revealed to InformationWeek that "More than 25 years ago, a couple of former spooks showed me how they could capture a user's ATM PIN, from a van parked across the street, simply by capturing and decoding the electromagnetic signals generated by every keystroke," O'Farrell said. "They could even capture keystrokes from computers in nearby offices, but the technology wasn't sophisticated enough to focus in on any specific computer."
Physical injury
![Computer Workstation Variables](https://upload.wikimedia.org/wikipedia/commons/3/35/Computer_Workstation_Variables.jpg)
The use of any keyboard may cause serious injury (such as
carpal tunnel syndrome
Carpal tunnel syndrome (CTS) is the collection of symptoms and signs associated with median neuropathy at the carpal tunnel. Most CTS is related to idiopathic compression of the median nerve as it travels through the wrist at the carpal tunn ...
or other
repetitive strain injuries
A repetitive strain injury (RSI) is an injury to part of the musculoskeletal or nervous system caused by repetitive use, vibrations, compression or long periods in a fixed position. Other common names include repetitive stress disorders, cumula ...
) to the hands, wrists, arms, neck or back. The risks of injuries can be reduced by taking frequent short breaks to get up and walk around a couple of times every hour. Users should also vary tasks throughout the day, to avoid overuse of the hands and wrists. When typing on a keyboard, a person should keep the shoulders relaxed with the elbows at the side, with the keyboard and mouse positioned so that reaching is not necessary. The chair height and keyboard tray should be adjusted so that the wrists are straight, and the wrists should not be rested on sharp table edges. Wrist or palm rests should not be used while typing.
Some
adaptive technology
Assistive technology (AT) is a term for assistive, adaptive, and rehabilitative devices for people with disabilities and the elderly. Disabled people often have difficulty performing activities of daily living (ADLs) independently, or even with ...
ranging from special keyboards, mouse replacements and pen tablet interfaces to speech recognition software can reduce the risk of injury. Pause software reminds the user to pause frequently. Switching to a much more ergonomic mouse, such as a
vertical mouse or joystick mouse may provide relief.
By using a
touchpad
A touchpad or trackpad is a pointing device featuring a tactile sensor, a specialized surface that can translate the motion and position of a user's fingers to a relative position on the operating system that is made output to the screen. Touchp ...
or a stylus pen with a graphic tablet, in place of a mouse, one can lessen the repetitive strain on the arms and hands.
See also
*
List of mechanical keyboards
Mechanical keyboards (or mechanical-switch keyboards) are computer keyboard
A computer keyboard is a peripheral input device modeled after the typewriter keyboard which uses an arrangement of buttons or keys to act as mechanical levers or ...
*
Keyboard layout
A keyboard layout is any specific physical, visual or functional arrangement of the keys, legends, or key-meaning associations (respectively) of a computer keyboard, mobile phone, or other computer-controlled typographic keyboard.
is the actua ...
**
AZERTY
AZERTY () is a specific keyboard layout, layout for the characters of the Latin alphabet on typewriter keys and computer keyboard (computing), keyboards. The layout takes its name from the first six letter (alphabet), letters to appear on the fir ...
**
QWERTY
QWERTY () is a keyboard layout for Latin-script alphabets. The name comes from the order of the first six Computer keyboard keys#Types, keys on the top left letter row of the keyboard ( ). The QWERTY design is based on a layout created f ...
**
QWERTZ
The QWERTZ or QWERTZU keyboard is a typewriter and keyboard layout widely used in Central Europe. The name comes from the first six letters at the top left of the keyboard: ( ).
Overview
The main difference between QWERTZ and QWERTY is tha ...
*
Keyboard mapping
A keyboard layout is any specific physical, visual or functional arrangement of the keys, legends, or key-meaning associations (respectively) of a computer keyboard, mobile phone, or other computer-controlled typographic keyboard.
is the actua ...
References
{{DEFAULTSORT:Keyboard Technology
Computer keyboards