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The classic example of an assistive technology that has improved everyone's life is the "curb cuts" in the sidewalk at street crossings. While these curb cuts surely enable pedestrians with mobility impairments to cross the street, they have also aided parents with carriages and strollers, shoppers with carts, and travellers and workers with pull-type bags, not to mention skateboarders and inline skaters.

Consider an example of an assistive technology. The modern telephone is not accessible to people who are deaf or hard of hearing. Combined with a text telephone also known as a TDD [Telephone Device for the Deaf] and in the USA generally called a TTY [TeleTYpewriter] , which converts typed characters into tones that may be sent over the telephone line, the deaf person is able to communicate immediately at a distance.

Together with "relay" services where an operator reads what the deaf person types and types what a hearing person says the deaf person is then given access to everyone's telephone, not just those of people who possess text telephones. Many telephones now have volume controls, which are primarily intended for the benefit of people who are hard of hearing, but can be useful for all users at times and places where there is significant background noise. Another example: calculators are cheap, but a person with a mobility impairment can have difficulty using them.

Speech recognition software could recognize short commands and make use of calculators a little easier. People with cognitive disabilities would appreciate the simplicity; others would as well. Toys which have been adapted to be used by children with disabilities, may have advantages for "typical" children as well. The Lekotek movement assists parents by lending assistive technology toys and expertise to families. Telecare is a particular sort of assistive technology that uses electronic sensors connected to an alarm system to help caregivers manage risk and help vulnerable people stay independent at home longer.

A good example would be the systems being put in place for senior people such as fall detectors, thermometers for hypothermia risk , flooding and unlit gas sensors for people with mild dementia. The principle being that these alerts can be customised to the particular person's risks. When the alert is triggered, a message is sent to a carer or contact centre who can respond appropriately. The range of sensors is wide and expanding rapidly. Technology similar to Telecare can also be used to act within a person's home rather than just to respond to a detected crisis.

Using one of the examples above, unlit gas sensors for people with dementia can be used to trigger a device that turns off the gas and tells someone what has happened. This is safer than just telling an external person that there is a problem. Designing for people with dementia is a good example of where the design of the interface of a piece of assistive technology AT is critical to its usefulness.

It is important to make sure that people with dementia or any other identified user group are involved in the design process to make sure that the design is accessible and useable. In the example above, a voice message could be used to remind the person with dementia to turn of the gas himself, but who's voice should be used, and what should the message say?

Questions like these must be answered through user consultation, involvement and evaluation. Reduce the discomfort from injuries related to Height-adjustable trolley. Allows precise adjustment, via a handle, of excessive keyboard use wristrests are often built in as well. Have a handful of keys one per digit per hand equipment. Adjustable keyboard and monitor arms.

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Attaches to a table and swings Expanded keyboards. Keys are larger and more widely spaced. Compact and miniature keyboards. A smaller version of the standard Footrests. An ergonomic keyboard layout, control. Stabilises the arm. Arm supports. Take the weight of the arm and let the user move Height-adjustable computer table across the keyboard to access the keys. It fits over the keyboard to help prevent unintentional keypresses.

Allows characters or commands to be typed a feature of Microsoft Windows 95 onwards. Adjusts the speed at without having to hold down a modifier key Shift, Ctrl, Alt while which a character repeats when you hold down a key. ToggleKeys is a feature of Microsoft Windows 95 onwards. A high FilterKeys is a feature of Microsoft Windows 95 onwards. Windows 95 onwards. Adjusts the amount of time that elapses before a character repeats when you hold down a key.

Accessing the mouse Hardware Wristrests and supports. Wristrests support the hand so that there is Joysticks. The stick is moved directly with the fingers or foot, nose, less strain on the wrist; arm supports support the arm yet still permit elbow etc to control the mouse pointer. Keyboard shortcuts. A combination of keys is used for operations Graphics tablets. The stylus pen, linked to the tablet, is moved with commonly done using the mouse. An upside-down mouse where the ball is moved directly Touch pads.

Flat touch sensitive surface operated with the finger to with the fingers or foot, nose, elbow etc to control the mouse control the mouse pointer. Touch screens.

The user can touch objects directly on the screen to move them around. Head control. Use head movement to control the mouse pointer. MouseKeys is a feature of Microsoft Windows 95 onwards. Configures ClickLock is a feature of Microsoft Windows. Locks a mouse button the numeric keypad at the right-hand side of the keyboard to control down so that items can be dragged around the screen. Mouse speed is a feature of Microsoft Windows. Sets how far and fast Macros is a feature of Microsoft Word. A particular sequence of the pointer moves on the screen. Changes can be made pressing a combination of keys.

Switch access and switches Switches allow access to computers for people with severe physical or Switch mounting. Used to mount a switch sometimes in conjunction cognitive difficulties. Mimics a keyboard keystroke or mouse click. Switch interface. Used as an interface to connect a switch to the Switch accessible software. Software which is accessible via a switch. Visual impairment Hardware choice of appropriate hardware will depend on the Fuser. To produce tactile materials, e. Full keyboard stickers. High-contrast, enlarged print adhesive Standalone Reading Aid.

A unit which integrates a scanner, Optical keyboard stickers - white on black, black on white and black on Character Recognition OCR software and speech software. The yellow sets available. Large print keyboard. A device used in conjunction with Optical Character white on black, black on white and black on ivory versions available. Recognition OCR software. The printed document is scanned and Locator dots. F and J, on the keyboard. Moves mouse pointer, plus middle wheel button is used as recognisable text. Refreshable Braille display. An electronic tactile device which is Large screen monitor.

Produces a larger-than-normal image. A line of cells, that move up Adjustable task lamp. Lamp, using fluorescent bulb, shines directly and down to represent a line of text on the computer screen, enables onto the paper and can be adjusted to suit. Holds printed material in near vertical position for easier Electronic Notetaker. Printed Braille display. Embosses Braille output from a computer by image is displayed onto a screen. It connects to a computer in the same way Modified cassette recorder. To record a lecture, own thoughts, ideas, as a text printer.

Perkins Brailler. To manually emboss Grade 1 or 2 Braille. Desktop compact cassette dictation system. To allow audio cassette playback with the aid of a foot pedal. Converts what is happening on the computer screen level of functional vision into synthesised speech. Customised Microsoft Windows. Changes the desktop, short-cut icons, Optical Character Recognition. Converts the printed word into menu bars and scroll bars. Customised mouse pointers and toolbars. Changes the size, colour Braille translation. Screen magnifier. Enlarges the image on the computer screen.

The Touch typing. A combination of keys also have supportive synthetic speech. Simple paper or object based systems, i. Light-tech systems.

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Simple voice output devices, which require a battery; although no sophisticated charging mechanism is required. High-tech systems. Sophisticated voice output devices, which require a battery, as well as training and ongoing support. Normalmente la luce passa attraverso il cristallo e viene riflessa pixel bianco.

Il cristallo si volta lentamente, quindi non ci sono effetti di flicker. Ora sono a colori, veloci e a costi ragionevoli. Crearono il mercato degli orologi digitali negli anni Negli anni 90 hanno creato il mercato dei portatili e dei PDA. Molto pesanti e scomodi. Rende effetti 3D molto credibili. Ogni lato si illumina in maniera indipendente. Touchscreen A touch screen is an input device that allows the user to interact with the computer by touching the display screen.

It was first used on a dedicated console with the Game. Com from Tiger. Nintendo popularised it for use in video games with the Nintendo DS; other systems including the Tapwave Zodiac as well as the vast majority of PDAs have also included this feature. Modern touch screens use a thin, durable, transparent plastic sheet overlayed onto the glass screen.

The location of a touch is calculated from the capacitance for the X and Y axes, which varies based upon where the sheet is touched. Touchscreen panels are display overlays which are typically either pressure-sensitive resistive , electrically-sensitive capacitive , acoustically-sensitive SAW - surface acoustic wave or photo-sensitive infra-red. Such displays can be attached to computers or, as terminals, to networks. Touchscreens have become commonplace since the invention of the electronic touch interface in by Dr.

Samuel C. The popularity of smart phones, PDAs, portable game consoles and many types of information appliances is driving the demand for, and the acceptance of, touchscreens. The HP was among one of the world's earliest commercialized touch screen computers. It actually does not have a touch screen in the strict sense, but a 9" Sony CRT surrounded by infrared transmitters and receivers which detect the position of any non-transparent object on the screen.

Touchscreens are popular in heavy industry and in other situations, such as museum displays, where keyboards and mice do not allow a satisfactory intuitive, rapid or accurate interaction by the user with the display's content. The Nintendo DS uses a touchscreen as a primary controlling device. Historically, the touchscreen sensor and its accompanying controller-based firmware have been made available by a wide array of after-market system integrators and not by display, chip or motherboard manufacturers.

With time, however, display manufacturers and System On Chip SOC manufacturers worldwide have acknowledged the trend toward acceptance of touchscreens as a highly desirable user interface component and have begun to integrate touchscreen functionality into the fundamental design of their products. There are a number of types of touch screen technology: Optical Imaging: this is a relatively-modern development in touch screen technology, two or more image sensors are placed around the edges usually the corners of the screen. Infrared backlights are placed in the camera's field of view on the other sides of the screen.

A touch shows up as a shadow and each pair of cameras can then be triangulated to locate the touch. This technology is growing in popularity, due to its scalability, versatility, and affordability, especially for larger units. Resistive: a resistive touch screen panel is coated with a thin metallic electrically conductive and resistive layer that causes a change in the electrical current which is registered as a touch event and sent to the controller for processing.

Resistive touch screen panels are not affected by outside elements such as dust or water and are the most commonly used today. Resistive LCD touchscreen monitors rely on a touch overlay, which is composed of a flexible top layer and a rigid bottom layer separated by insulating dots, attached to a touchscreen controller.

The inside surface of each of the two layers is coated with a transparent metal oxide coating ITO that facilitates a gradient across each layer when voltage is applied. Pressing the flexible top sheet creates electrical contact between the resistive layers, producing a switch closing in the circuit. The control electronics alternate voltage between the layers and pass the resulting X and Y touch coordinates to the touchscreen controller. The touchscreen controller data is then passed on to the computer operating system for processing.

Resistive touchscreen technology possesses many advantages over other alternative touchscreen technologies acoustic wave, capacitive, Near Field Imaging, infrared. Highly durable, resistive touchscreens are less susceptible to contaminants that easily infect acoustic wave touchscreens. In addition, resistive touchscreens are less senstive to the effects of severe scratches that would incapacitate capacitive touchscreens. For industrial applications, resistive touchscreens are much more cost-effective than Near Field Imaging touchscreens are. Because of its versatility and cost-effectiveness, resistive touchscreen technology is the touch technology of choice for many markets and applications.

Resistive touchscreens are used in food service, retail point-of-sale POS , medical monitoring devices, industrial process control and instrumentation, portable and handheld products. FastPoint LCD touchscreens specifically employ 8-wire resistive technology because of its benefits over its counterparts. In contrast to 5-wire resistive touchscreens, 8-wire touchscreens do not experience spacer dots and Newton rings. Additionally, 8-wire resistive touchscreens are not susceptible to problems caused by high-level short- term variances and axis linearity and drift.

Polyester Film 2. Upper Resistive Circuit Layer 3. Lower Resistive Circuit Layer 5. Insulating Dots 6. Touching the overlay surface causes the 2 Upper Resistive Circuit Layer to contact the 4 Lower Resistive Circuit Layer, producing a circuit switch from the activated area. The touchscreen controller gets the alternating voltages between the 7 two circuit layers and converts them into the digital X and Y coordinates of the activated area.

Surface wave: Surface wave technology uses ultrasonic waves that pass over the touch screen panel. When the panel is touched, a portion of the wave is absorbed. This change in the ultrasonic waves registers the position of the touch event and sends this information to the controller for processing. Surface wave touch screen panels can be damaged by outside elements: contaminants on the surface can also interfere with the functionality of the touchscreen. The sensor therefore exhibits a precisely controlled field of stored electrons in both the horizontal and vertical axes - it achieves capacitance.

The human body is also an electrical device which has stored electrons and therefore also exhibits capacitance. When the sensor's 'normal' capacitance field its reference state is altered by another capacitance field, i. Capacitive sensors must be touched with a conductive device being held by a bare hand or a finger, unlike resistive and surface wave panels that can use anything that can point, such as a finger or stylus.

Capacitive touch screens are not affected by outside elements and have high clarity. Controller alternates the voltage gradient alternatively horizontally and vertically in order to obtain x and y coordinates o current values at every corner of the screen. Infrared: an infrared touch screen panel employs one of two very different methodologies.

One method used thermal induced changes of the surface resistance. This method was sometimes slow and required warm hands. Another method is an array of vertical and horizontal IR sensors that detected the interruption of a modulated light beam near the surface of the screen. Dispersive Signal Technology: this is the newest technology, introduced in It uses sensors to detect the mechanical energy in the glass that occur due to a touch. Complex algorithms then interpret this information and provide the actual location of the touch. The technology claims to be unaffected by dust and other outside elements, including scratches.

Since there is no need for additional elements on screen, it also claims to provide excellent optical clarity. Also, since mechanical vibrations are used to detect a touch event, any object can be used to generate these events, including fingers and styli. The technology is still quite new and is not currently widely available.

Strain Gauge: in a strain gauge configuration the screen is spring mounted on the four corners and strain gauges are used to determine deflection when the screen is touched. This technology can also measure the Z-axis. Typical application falls in protecting new touch-screen railway ticket machines from vandalism. Touchscreen deployment Virtually all of the significant touchscreen technology patents were filed during the 's and 's and have expired. Touchscreen component manufacturing and product design are no longer encumbered by royalties or legalities with regard to patents and the manufacturing of touchscreen- enabled displays on all kinds of devices is widespread.

With the growing acceptance of many kinds of products with an integral touchscreen interface the marginal cost of touchscreen technology is routinely absorbed into the products that incorporate it and is effectively eliminated. As typically occurs with any technology, touchscreen hardware and software, has sufficiently matured and been perfected over more than three decades to the point where its reliability is unassailable.

As such, touchscreen displays are found today in airplanes, automobiles, gaming consoles, machine control systems, appliances and handheld display devices of every kind. Industrial: Touch can be applied virtually anywhere on a factory floor. From process automation to quality control, touch is fast becoming a preferred solution.

Touch- enabled products provide users with a space saving, NEMA sealable option for challenging environments. Healthcare: Instrumental in healthcare environments, touch solutions add convenience and reliability to applications including patient records, nurse stations, and patient monitoring systems. Point-of-Sale: Intuitive touch solutions offer numerous opportunities to retail and point-of- sale environments including cash registers in retail outlets and food ordering systems in bars and restaurants.

Touch solutions can also be beneficial for kitchen staff filling orders and for seating charts and reservation schedules. Financial: From Main Street to Wall Street, touch screens help simplify the complex world of banking and finance. ATMs were at the forefront of adopting touch screen technology for their intuitive ease-of-use and durability in public places. On the stock exchange floor and at brokerage houses, touch-based applications help accelerate the trading process while providing on-line trading information.

Self-Service Kiosks: Touch-enabled kiosks provide self-service capabilities as well as access to information hours a day, 7 days a week. Self-service kiosks are used to provide services ranging from buying theater tickets, to viewing information directories, to self check-in at airports and self check-out in retail environments. The result is a more intuitive, natural, and multisensory experience. Immersion proprietary technology causes the touchscreen to vibrate, creating the perception of pressing physical switches, emulating crisp qualities and particular force and push-away characteristics.

Based on software or firmware programming, touching different virtual objects on the screen produces the desired, context-sensitive feel for the user. The programmability of TouchSense technology can be used to further enhance usability, particularly for noisy or distracting environments. Rich touch sensations can be created by combining individual effects of varying frequency, waveform, magnitude, and duration. For aerospace and automotive applications, even a small improvement in ease of use, error reduction, or glance time can have a significant impact on safety. User interaction is about creating an effective human- machine interface HMI that leads to rapid and accurate task completion or a more satisfying experience.

Research has found that, when compared to single-mode voice and visual applications, multimodal applications are easier and more intuitive to use. Yet, in the world of computers and digital devices and controls, haptic feedback is often lost. This kind of wave is commonly used in piezoelectric devices called SAW devices in electronics circuits.

SAW devices are employed as filters, oscillators and transformers based on the transduction of acoustic waves. Discovered in by Lord Rayleigh who reported the surface acoustic wave mode of propagation and in his classic paper predicted the properties of these waves. This coupling strongly affects the amplitude and velocity of the wave allowing SAW sensors to directly sense mass and mechanical properties.

Electronic devices employing the SAW normally utilize one or more interdigital transducers IDTs to convert acoustic wave to electrical signal and vice versa utilizing the piezoelectric effect of certain materials quartz, lithium niobate, lithium tantalate, LGS etc. These devices are fabricated utilizing common processes used in the manufacture of silicon integrated circuits. SAW filters have enjoyed successful application in the booming cellular telephones market and provide significant advantages in performance, cost, and size over other filter technologies digital signal processors, quartz crystals bulk wave , LC filters, and waveguide filters.

Significant research has been done in the last 20 years in the area of surface acoustic wave sensors. Sensor applications include all areas of sensing such as chemical, optical, thermal, pressure, acceleration, torque and biological. SAW sensors have seen limited commercial success to date but are commonly commercially available for some applications such as touchscreen displays. More than 40 worldwide patents relating to the use of SAW sensors in the automotive industry have been filed by UK intellectual property IP company Transense Technologies.

These batteryless sensors are expected to replace lithium ion battery powered tyre pressure sensors shortly, while the company's torque SAW sensors will be used to facilitate a number of engine control applications that have not been possible before. Keyboard and mouse The keyboard and mouse are typical input devices for a personal computer and are currently the main game controllers for computer games.

Some video game consoles also have the ability to function with a keyboard and a mouse. The computer keyboard is modeled after the typewriter keyboard and was designed for the input of written text. A mouse is a handheld pointing device used in addition to the keyboard. For games, the keyboard typically controls movement of the character while the mouse is used to control the game camera or used for aiming.

The numeric keypad found on the keyboard is also used as a game controller and can be found on a number of separate devices, most notably early consoles, usually attached to a joystick or a paddle. The keypad is a small grid of keys with at least the digits Computer keyboard A computer keyboard is a peripheral modeled after the typewriter keyboard. Keyboards are designed for the input of text and characters, and also to control the operation of a computer.

Physically, computer keyboards are an arrangement of rectangular or near-rectangular buttons, or "keys". Keyboards typically have characters engraved or printed on the keys; in most cases, each press of a key corresponds to a single written symbol. However, to produce some symbols requires pressing and holding several keys simultaneously, or in sequence; other keys do not produce any symbol, but instead affect the operation of the computer, or the keyboard itself.

See input method editor. Other keys can produce actions when pressed, and other actions are available by simultaneously pressing more than one action key. These different keyboard layouts arise because different people need easy access to different symbols; typically, this is because they are writing in different languages, but specialized keyboard layouts for mathematics, accounting, and computer programming do exist. The number of keys on a keyboard generally varies from the standard keys to the windows keyboards all the way up to keys with many programmable keys.

There are also compact variants that have fewer than 90 keys. They are normally found in laptops or in desktop computers with space constraints. Even in countries where different alphabets or writing systems are in use, the physical layout of the keys is often quite similar e. Additional keys and "Internet" keyboards Most modern computer keyboards including those on the PC and Apple Mac are based on these standard versions, but include additional keys not normally found on typewriters, such as function keys, a numeric keypad, and so on.

In recent years, so-called "Internet keyboards" have also become popular. These include extra buttons for specific applications or functions typically a browser or email client. Plug Types There are a few different ways of connecting a keyboard which have evolved over the years. Alternatives A standard keyboard is physically quite large, as each key must remain large enough to be easily pressed by fingers. Other types of keyboards have been proposed for small portable equipment where a standard keyboard is too large. One way to reduce the number of keys is to use chording, i.

As an example, the GKOS keyboard has been designed for small wireless devices. Other two-handed alternatives more akin to a gaming controller, such as the AlphaGrip, are also used as a way to input data and text. Usage Microsoft On-Screen Keyboard is software designed for users with limited mobility. In normal usage, the keyboard is used to type text into word processor, text editor, or any other textbox. In modern computers the interpretation of keypresses is generally left to the software.

Modern keyboards distinguish each physical key from every other and report all keypresses and releases to the controlling marco. This flexibility is not often taken advantage of and it usually does not matter, for example, whether the left or right shift key is held down in conjunction with another character. Commands A keyboard is also used to type commands in a computer. With current versions of Windows, this brings up a menu-window including options for handling currently-running applications and shutting down the computer, amongst other things.

Games A keyboard is one of the primary methods of control in computer games. For instance, the arrow keys or a group of letters resembling the pattern of the arrow keys, like WASD, can be used for movement of a game character. In many games keys can be configured to the user's preferences. Alphabet keys are also sometimes used to perform actions starting with that letter.

Keyboards are less than ideal when many keys are to be pressed at once, as the limited circuitry means that only a certain number of keys will register at one time. An obvious example of this is phantom key blocking. On older keyboards, due to the circuit design, sometimes pressing three keys simultaneously results in a 4th keypress being registered.

Modern keyboards prevent this from happening by blocking the 3rd key in certain key combinations, but while this prevents phantom input, it also means that when two keys are depressed simultaneously, many of the other keys on the keyboard will not respond until one of the two depressed keys is lifted. How it works The following briefly describes a "dome-switch" keyboard sometimes misleadingly referred to as a membrane keyboard , the most common type in use today:- 1.


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When a key is pressed, it pushes down on a rubber dome sitting beneath the key. A conductive contact on the underside of the dome touches and hence connects a pair of conductive lines on the circuit below. This bridges the gap between them and allows current to flow i. A scanning signal is emitted by the chip along the pairs of lines to all the keys.

When the signal in one pair becomes different, the chip generates a "make code" corresponding to the key connected to that pair of lines. The code generated is sent to the computer either via a keyboard cable using on-off electrical pulses to represent bits or over a wireless connection. A chip inside the computer receives the signal bits and decodes them into the appropriate keypress. The computer then decides what to do on the basis of the key pressed e. Other types of keyboard function in a similar manner, the main differences being how the individual key-switches work.

For more detail, refer to the "Keyboard technology" article. I tasti sono disposti in modo da evitare incastri fra i martelletti. Le tastiere tradizionali impongono posture innaturali, che possono indurre vari disturbi. Nelle tastiere ad accordi ad ogni dito corrisponde un singolo tasto e ad ogni carattere corrisponde una combinazione di tasti accordo , e non un tasto singolo. Since there are so many switches needed usually about 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. Types 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 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 share a certain degree of liquid resistance with their membrane ancestors. 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. These two keyboards use ALPS switches. Cherry corporation of Germany also makes mechanical switches used in special purpose and high end keyboards. 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 utilitizes membrane- sheet switches, much like those found in a dome-switch keyboard. The buckling spring mechanism U. Patent 4,, 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 , two years after spawning Lexmark, IBM transferred its keyboard operations to the daughter company. When a key is depressed, it moves a magnet, which is detected by a solid-state Hall-effect 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.

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 , they have been supplanted by the more tactile dome and mechanical switch keyboards.

It should be noted, however, that 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. 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.

Very little, if any, tactile feedback is felt when using such a keyboard, and error-free blind typing can be difficult. Membrane keyboards, which work by electrical contact between the keyboard surface and the underlying circuits when keytop areas are pressed, were used with some early s home computers, and have been much used in consumer electronics devices. The keyboards are very inexpensive to mass produce, and are more resistant against dirt and liquids than most other keyboards, but due to the low or non-existent amount of tactile feedback provided, most people have difficulty typing with them, especially when large numbers of characters need to be typed.

Chiclet keyboards were a slight improvement, at least allowing individual keys to be felt to some extent. Smaller, specialised membrane keyboards, typically numeric-and-a-few-control-keys only, have been used in access control systems for buildings and marco. The expression is also sometimes used in connection with modern PC keyboards which utilise dome switch technology. Although the lower layers in some dome-switch keyboards are essentially the same as the membrane keyboard, the dome-switch keyboard includes additional upper layers rubber domes and solid key-caps.

How it works As can be seen from the diagram below, the membrane keyboard basically consists of three layers; two of these are membrane layers containing conductive traces. The center layer is a "spacer" containing holes wherever a "key" exists. It keeps the other two layers apart. Cross-section diagram of a typical membrane keyboard. The thickness of the bottom three layers has been exaggerated for clarity; in reality, they are not much thicker than pieces of paper or cardboard. Under normal conditions, the switch key is open, because current cannot cross the non-conductive gap between the traces on the bottom layer.

However, when the top layer is pressed down with a finger , it makes contact with the bottom layer. The conductive traces on the underside of the top layer can then bridge the gap, allowing current to flow. The switch is now "closed", and the parent device registers a keypress. Roll-up keyboard Some keyboards are designed out of flexible materials that can roll up in a tight bundle. 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. 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 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. It takes its name from the first six letters seen in the keyboard's top first row of letters. Frequently used pairs of letters were separated in an attempt to stop the typebars from intertwining and becoming stuck, thus forcing the typist to manually unstick the typebars and also frequently blotting the document[1].

QWERTY also attempted to alternate keys between hands, allowing one hand to move into position while the other hand strikes home a key. This sped up both the original double-handed hunt-and-peck technique and the later touch typing technique; however, single-handed words such as stewardesses and monopoly show flaws in the alternation. Minor changes to the arrangement are made for other languages; for example, German keyboards add umlauts to the right of "P" and "L", and interchange the "Z" and "Y" keys both because "Z" is a much more common letter than "Y" in German the letter seldom appearing except in borrowed words , and because "T" and "Z" often appear next to each other in the German language; consequently, they are known as QWERTZ keyboards.

Alternative keyboard layouts Because modern keyboards do not suffer from the problems of older mechanical keyboards, the QWERTY layout's separation of frequently used letter pairs is no longer strictly necessary. Several alternative keyboard layouts, such as Dvorak Simplified Keyboard arrangement designed by Drs. August Dvorak and William Dealey and patented in , have been designed to increase a typist's speed and comfort, largely by moving the most common letters to the home row and maximizing hand alternation.

The effectiveness of these layouts is disputed. Some studies [2] have shown that alternative methods are more efficient, but Dvorak and other alternative typists most often cite comfort as the greatest advantage. Opponents point out that August Dvorak stood to gain from the success of his layout, and that he may have perpetuated his "efficiency myth" to increase his financial gains. Computer users also need to unlearn the habit of pressing key shortcuts for example: Ctrl-C for copy, Ctrl-X for cut, Ctrl-V for paste, on Microsoft Windows , though some programs and operating systems allow the use of alternate layouts combined with QWERTY shortcuts.

Opponents of alternative keyboard designs most often point to QWERTY's ubiquity as a deciding factor, because the costs incurred by using the supposedly inefficient layout are much less than those of retraining typists. Besides the Dvorak layout, there are many other newer alternative keyboard layouts, but those layouts have not gained widespread use.

The words sweaterdresses and aftercataracts are longer and can also be typed with only the left hand, but they are not in all dictionaries. This is off the charts, and they help to fuel the theories that there are some computer hackers that actually go through keyboards quite quickly. Mouse or Mice? Operating a mechanical mouse. A mouse is a handheld computer pointing device, designed to sit under one hand of the user and detect movement relative to its supporting surface. The mouse's 2D motion is typically translated into the motion of a pointer on a display.

The name "mouse", coined at the Stanford Research Institute, derives from the resemblance of early models which had a cord attached to the rear part of the device, suggesting the idea of a tail to the common small rodent of the same name.

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The mouse was invented by Douglas Engelbart of Stanford Research Institute in , after extensive usability testing. Engelbart's team called it "bug". The other devices were designed to exploit other body movements—for example, head-mounted devices attached to the chin or nose—but ultimately the mouse won out because of its simplicity and convenience. The first, bulky, mouse pictured used two gear wheels perpendicular to each other: the rotation of each wheel was translated into motion along one axis.

At the time, Engelbart intended that users would hold the mouse continuously in one hand and type on a five-key chord keyset with the other. Mechanical mice The so-called "ball mouse" was later invented in the early s by Bill English while he was working for Xerox PARC; it replaced the external wheels with a single ball that could rotate in any direction. The ball's motion, in turn, was detected using perpendicular wheels housed inside the mouse's body.

This variant of the mouse resembled an inverted trackball and was the predominant form used with personal computers throughout the s and s.

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The Xerox PARC group also settled on the modern technique of using both hands to type on a full-size keyboard and grabbing the mouse as needed. A spin-off of EPFL, marco. The major movement translation techniques are by optical, mechanical and inertial sensors. Optical mice An optical mouse uses a light-emitting diode and photodiodes to detect the movement of the underlying surface, rather than moving some of its parts as in a mechanical mouse. Early optical mice, circa , were of two types. From left to right: Corporation, used an infrared LED and a four-quadrant infrared sensor to detect grid lines printed on Opposing track wheels by Engelbart, Nov.

Predictive algorithms in the CPU of the mouse Ball and wheel by Rider, Sept. Others, invented by Richard F. Lyon and sold by Ball and two rollers with spring by Xerox, used a pixel visible-light image sensor with integrated motion detection on the same chip Opocensky, Oct. 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 rotated, while the Lyon mouse used the x-y coordinate system of the mouse body, as mechanical mice do. As computing power grew cheaper, it became possible to embed more powerful special-purpose image processing chips in the mouse.

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 pointer and eliminating the need for a special mouse pad. This advance paved the way for widespread adoption of optical mice. Modern surface-independent optical mice work by using an optoelectronic sensor to take successive pictures of the surface on which the mouse is operating.

Most of these mice use LEDs to illuminate the surface that is being tracked; LED optical mice are often mislabeled as "laser mice". Changes between one frame and the next are processed by the image processing part of the chip and translated into movement on the two axes using an optical flow algorithm.

Optomechanical mice detect movements of the ball optically, giving the precision of optical without The optical sensor from a Microsoft Wireless the surface compatibility problems, whereas optical mice detect relative movement of the surface by IntelliMouse Explorer v. This mouse uses a small laser instead of a LED. The new technology can increase the resolution of the image taken by the mouse. Gamers have complained that the MX does not respond immediately to movement after it is picked up, moved, and then put down on the mouse pad.

Newer revisions of the mouse do not seem to suffer from this problem, which is a power-saving feature almost all optical marco. Since it is a wireless mouse, the engineers designed it to save as much power as possible. In order to do this, the mouse blinks the laser when in standby mode 8 seconds after the last motion.

This function also increases the laser life. Optical versus mechanical mice Optical mice supporters claim optical rendering works better than mechanical mice, requires no maintenance and lasts longer due to fewer moving parts. Optical mice do not normally require any maintenance other than removing debris that might collect under the light emitter, although cleaning a dirty mechanical mouse is fairly straightforward too. Mechanical mice supporters point out that optical mice generally cannot track on glossy and transparent surfaces, including many commercial mouse pads, causing them to periodically "spin" uncontrollably during operation.

Power conservation is typically not an issue for cabled mice. At the time of writing , mechanical mice have lower average power demands than their optical conterparts. This is of no practical concern for cabled mice, but has an impact on battery-powered wireless models. Since optical mice render movement based on an image the LED reflects, performance on multi-colored mousepads may be unreliable.

However, they will outperform mechanical mice on uneven, slick, squishy, sticky or loose surfaces, and generally in mobile situations where mouse pads are not available. Inertial Mice Inertial mice detect movement through a gyroscope, for every axis supported. Usually cordless, they often have a switch to deactivate the movement circuitry between use, allowing the user freedom of movement without affecting the pointer position.

Buttons In contrast to the motion-sensing mechanism, the mouse's buttons have changed little, varying mostly in shape, number, and placement. Engelbart's very first mouse had a single button; this was soon increased to three at Xerox PARC, but reduced to two for Xerox products. Apple reduced it back to one button with the Macintosh in , while Unix workstations from Sun and others used three buttons. Commercial mice usually have between one and three buttons, although in the late s some mice had five or more.

Most popular are mice with two buttons. The most common purpose for the second button is to invoke a contextual menu in the computer's software user interface, which contains options specifically tailored to the interface element over which the mouse pointer is positioned. By default, the primary mouse button is located on the left hand side of the mouse, for the benefit of right handed users. On systems with three-button mice, pressing the center button a middle click is often used as a convenience to map the action to a commonly used action, or a macro.

In the X Window System, middle clicking pastes the contents of the primary buffer at the pointer's position. Many two-button mice are configured to emulate a three-button mouse by clicking both the right and left buttons simultaneously. Middle-clicks are often used as a spare button in case a function is not allocated easily. Additional buttons Mice have been built with five or more buttons. Depending on the user's preferences, the extra buttons may allow forward and backward web navigation, scrolling through a browser's history, or other functions.

As with similar features in keyboards, however, these functions may not be marco. The additional buttons are generally more useful in computer games, where quick and easy access to a wide variety of functions for example, weapon-switching in first-person shooters can be very beneficial. Because mouse buttons can be mapped to virtually any function, keystroke, application or switch, they can make working with such a mouse more efficient and easier to use.

Douglas Engelbart's view of the optimal number of buttons was "as many as possible". The prototype that popularised the idea of three buttons as standard had that number only because "we couldn't find anywhere to fit any more switches". Wheels One major innovation in mouse buttons was the scroll wheel: a small wheel that can be rotated to provide immediate one-dimensional input. Usually, this input is translated into "scrolling" up or down within the active window or GUI element.

This is especially helpful in navigating a long document. The scroll wheel can often be pressed too, thus being in fact a third center button. Under many Windows applications, the wheel pressure activates autoscrolling and in conjunction with the control key Ctrl may zoom in and out applications which support this feature include Microsoft Word, Internet Explorer, Opera and Mozilla Firefox. The scroll wheel was first introduced by Microsoft IntelliMouse in The feature became a commercial success in when Office application suite and Internet Explorer browser started supporting the wheel scrolling feature.

After that the scroll wheel has become a norm. Some newer mouse models have two wheels, assigned to horizontal and vertical scrolling. Designs exist which make use of a "rocker" button instead of a wheel—a pivoting button that can be pressed at the top or bottom, simulating up and down respectively.

A more advanced form of mouse wheel is the tilt-wheel, found on some of the higher-end Logitech and Microsoft mice. Tilt wheels are essentially conventional mouse wheels that have been modified with a pair of sensors articulated to the tilting mechanism. These sensors are mapped, by default, to horizontal scrolling. In , the Apple Mighty Mouse introduced a third variety of built-in scrolling device: a "scroll ball", which is essentially a trackball embedded in the upper surface of the mouse, and is used like a two-dimensional scroll wheel.

This wireless mouse was worn on a ring around a finger, which enabled the thumb to access three buttons. The mouse was tracked in three dimensions by a base station. Publication Year. Display 1 - 20 from 43 results. Curve E Superfici. Tovena, F. Questo un libro di testo sulla geometria differenziale di curve e superfici, adatto agli studenti universitari del secondo e terzo anno dei corsi di Laurea in Matematica, Fisica, Ingegneria e Informatica.

Read More. Special Order. Special Order items are usually fulfilled in weeks. Cannot combine other item s in one order. Price incl. Local courier delivery with tracking number or collect from 90 lockers islandwide. Add to My List. Added to Cart. Calculus Problems. This book, intended as a practical working guide for calculus students, includes exercises.

It is designed for undergraduate students in Engineering, Mathematics, Physics, or any other field where rigorous calculus is needed, and will greatly benefit anyone seeking a problem-solving approach to calculus. Each chapter starts with a summary of the main definitions and results, which is followed by a selection of solved exercises accompanied by brief, illustrative comments.

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Introduction to Measure Theory and Functional Analysis. This book introduces readers to theories that play a crucial role in modern mathematics, such as integration and functional analysis, employing a unifying approach that views these two subjects as being deeply intertwined. This feature is particularly evident in the broad range of problems examined, the solutions of which are often supported by generous hints.

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Lo studio delle problematiche legate a tali strumenti richiede tecniche matematiche talvolta sofisticate e la maggior parte di queste tecniche sono legate alla teoria della Probabilit. Il presente libro inteso come testo e nasce dall'esperienza d'insegnamento degli autori.