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TECHNICAL SEMINAR:

TOUCH SCREEN TECHNOLOGY

Technical Seminar submitted in partial fulfillment of the requirements for theaward of the degree in

BACHELOR OF TECHNOLOGY

In

ELECTRONICS AND COMMUNICATION ENGINEERING

Submitted by

V. N SIVA KUMAR 07551A04A7

UNDER THE ESTEEMED GUIDANCE OF

Mr.M .RAMA KRISHNA

Asso. Professor

GODAVARI INSTITUTE OF ENGINEERING AND TECHNOLOGY

(Accredited by NBA , AFFILIATED to JNTU Kakinada)

Chaitanyanagar , NH-5 , RAJAHMUNDRY.


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Abstract:

TOUCH SCREEN

First computers became more visual, then they took a step further to understand

vocal commands and now they have gone a step further and became TOUCHY',

that is skin to screen.A touch screen is a display that can detect the presence and

location of a touch within the display area, generally refers to touch or contact to

the display of the device by a finger or hand. The screens are sensitive to

pressure; a user interacts with the computer by touching pictures or words on the

screen. Touchscreenscan also sense other passive objects, such as a stylus.A touch system consists of a touch Sensor that receives the touch input,

a Controller, and a Driver. The most commonly used touch technologies are the

Capacitive & Resistive systems. The other technologies used in this field are

Infrared technology, Near Field Imaging & SAW (surface acoustic wave

technology).

The touchscreen has two main attributes. First, it enables one to interact with

what is displayed directly on the screen, where it is displayed, rather than

indirectly with amouse or touchpad. Secondly, it lets one do so without requiring

any intermediate device, again, such as a stylus that needs to be held in the hand.

Such displays can be attached to computers or, as terminals to networks. They

also play a prominent role in many applications such as ATM's, point-of-

salesystems, industrialcontrols, casinos & public kiosks , the design of digital

appliances such as the personal digital assistant (PDA), satellite navigation

devices, mobile phones, and video games etc


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CONTENTS

1. INTRODUCTION

2. HISTORYOFTOUCH SCREEN

3. DEFINITIONOFTOUCHSCREEN

4. HOWDOES A TOUCHSCREENWORK?

5. TYPESOFTOUCHSCREEN

y RESISTIVE

y SURFACE ACOUSTICWAVE

y CAPACITIVE

y INFRARED

y OPTICAL IMAGING

y ACOUSTICPULSERECOGNITION

6.LATESTDEVELOPMENT

7. HOW ISTOUCH TECHNOLOGYDIFFERENT FROM OTHERS

8. APPLICATIONOFTOUCHSCREEN

9. CONCLUSION

10. REFERENCES


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Introduction:A touch screen is a computer display screen that is sensitive

to human touch, allowing a user to interact with the computer by touching

pictures or words on the screen.

A touch screen system includesa 1. Touch screen panel,

2.controller and

3.software driver.

The touch screen sensor is a clear panel that is designed to fit over a

PC. When the screen is touched, the sensor detects the voltage change and passes the

signal to the touch screen controller. The controller that reads & translates the sensor

input into aconventional bus protocol (Serial, USB) and a software driver which

converts the businformation to cursor action as well as providing systems utilities.

Touch screens are used with information kiosks, computer based training devices, and

systems designed to help individuals who have difficultymanipulating a mouse or

keyboard. The touch screen panel is a clear panel attachedexternally to the monitor that

plugs into a serial or Universal Serial Bus (USB) port or abus card installed inside the

computer.

Touch screen technology can be used as an alternative user interface

with applications that normally require a mouse, such as a Web browser. Some

applications are designed specifically for touch screen technology, often having

larger icons and links than the typical PC application. Monitors are available with

built-in touch screen technology or individuals can purchase a touch screen kit.


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History of Touch screen

Touchscreens emerged from corporate research labs in the second half

of the 1940s. Touchscreens first gained some visibility with the

invention of the computer-assisted learning terminal, which came out

in 1975 as part of the PLATO project. Touchscreens have subsequently

become familiar in everyday life.

The first "touch sensor wasfirst developed by Dr. Sam Hurst,

founder of Elographics, while he was an instructor at the University

of Kentucky in 1971. This sensor was called the "Elograph", and

was patented by The University of Kentucky Research Foundation.

The "Elograph" was not transparent as are touchscreens, but was

a significant mile-stone for touch technology.

The first true touch screen came on the scene in 1974, again

developed by Dr.Hurst, of Elographics. In 1977, Elographicsdeveloped and patented five-wire resistive technology, the most

popular touch screen technology in use today. On February 24,

1994, the company officially changed Its name from Elographics

to EloTouchSystems.

Definition:


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Whatare Touch Screens?

The touchscreen is the most user friendly PC interface. It is an

input device, a way to communicate with the PC. The user touches thescreen to select options presented on the screen. Associated hardware

and software are used to determine the location of the press.

Touch Screen

Touch is the easiest to learn and use of any available interface. Businesses both

large and small are using touch technology to create new products, reach new

markets, increase productivity, and ease the flow of information.


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A basic touch screen has three main components: a touch sensor, a controller,

and a software driver. The touch screen is an input device, so it needs to be

combined with a display and a PC or other device to make a complete

touchinput system.

1.Touch Sensor

A touch screen sensor is a clear glass panel with a touch responsive surface. The

touch sensor/panel is placed over a display screen so that the responsive area of the

panel covers the viewable area of the video screen. There are several different

touch sensor technologies on the market today, each using a different method todetect touch input. The sensor generally has an electrical current or signal going

through it and touching the screen causes a voltage or signal change.

This voltage change is used to determine the location of the touch to the screen.

How Does a TouchscreenWork?


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2.Controller

The controller is a small PC card that connects between the touch sensor and

the PC. It takes information from the touch sensor and translates it into

information that PC can understand. The controller is usually installed inside

the monitor for integrated monitors or it is housed in a plastic case for external

touch add-ons/overlays. The controller determines what type of

interface/connection you will need on the PC. Integrated touch monitors will

have an extra cable connection on the back for the touch screen. Controllers are

available that can connect to a Serial/COM port (PC) or to a USB port (PC or

Macintosh). Specialized controllers are also available that work with DVD

player and other devices.

3.Softwaredriver

The driver is a software update for the PC system that allows the

touch screen and computer to work together. It tells the computer's

operating system how to interpret the touch event information that is

sent from the controller. Most touch screen drivers today are a mouse-

emulation type driver. This makes touching the screen the same as

clicking your mouse at the same location on the screen. This allows

the touch screen to work with existing software and allows new

applications to be developed without the need for touch screen

specific programming.


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Types of Touch Screens

There are a variety of types of touch technology available but the major ones

include analog resistive, capacitive, infrared, acoustic wave and near field imaging

1. Resistive Touch Screens

Of these only one may actually be appropriate for your application.

Analog resistive touch technology is comprised of a glass overlay that fits exactly

to the shape of a flat panel display. The exterior face of the glass is coated with a

conductive, transparent layer. A clear, hard coated plastic sheet is then suspended

over the glass overlay. The interior face of the plastic sheet is also coated with a

conductive layer. Between the glass and the plastic sheet there are thousands of

tiny separator dots about one-one thousandth of an inch thick. When a stylus

applies pressure to the surface of the display, the two layers make contact and a

controller instantly calculates X and Y coordinates. This accounts for resistive

overlay's very high touch recognition resolution.


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An 8-wire analog resistive touch screen has held up to more than 35 million

touches in laboratory environments, although most are officially rated over 1

million touches. These systems can also be sealed to prevent dust or water

penetration.

Capacitive overlay systems operate by way of a conductive stylus and require the

use of the human finger or stylus. It is covered with a coat of transparent metal

oxide but the coat is bonded to a single sheet of glass making it susceptible to

scratches, which will jeopardize the integrity of the touch screen. A touch on the

screen creates a capacitive coupling, drawing an electrical current to the touch

point. However, as soon as a glove is placed over the hand, the touch screen is

rendered inoperable which eliminates it from being effective in many applications.

The resistive Touch Screen is set up in the following way

Resistive Touch Screens


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Formed to fit the shape of a display, the glass panel has a coating of uniform

resistivity. A polyester cover sheet is tightly suspended over the top of the glass,

separated from it by small, transparent insulating dots. The cover sheet has a hard,

durable coating on the outer side and a conductivecoating on the inner side. With a

light touch, the conductive coating makes electrical contact with the coating on the

glass.

The controller circuit applies a voltage gradient across the resistive surface of the

glass. The voltages at the point of contact are the analog representation of the

position touched. The controller digitizes these voltages and transmits them to

thecomputer for processing.


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Reading a 4-Wire Screen

By using 4 wires, a pair of wires on each layer, both signals of X and Y are

registered by the controller. When a touch occurs, the touch point introduces a pair

of voltages for X and Y direction. The Analog-to-Digital Converter (ADC), which

is located on the controller, is then converts these voltage positions into digital

numbers. The device driver calculates these digital numbers into display (X,Y)

coordinate. Puts the mouse cursor onto the (X,Y) coordinate. Also returns the

operating system with mouse left-button-down status, and left-button-up status

while untouched is occurred.

2.

4-wire Touch Screen

The x and y coordinates of a touch on a 4-wire touch screen can be read

in two steps. First, Y+ is driven high, Y is driven to ground, and the


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voltage at X+ is measured. The ratio of this measured voltage to

thedrive voltage applied is equal to the ratio of the y coordinate to the

height of the touch screen. The y coordinate can be calculated as

shown in Figure.

The x coordinate can be similarly obtained by drivingX+ high, driving X

to ground, and measuring the voltage at Y+. The ratio of this measured

voltage to the drive voltage applied is equal to the ratio of the x

coordinate to the width of the touch screen. Thismeasurement scheme

is shown in Figure

.

4-Wire Touch Coordinate Reading


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Advantages of Resistive

y Fast Response

y Pressure-activated by finger or gloved hand with a very light touch

y Durable hard-coat front surface can be non glare treated for reflection control or

polished for maximum clarity

y Touch screens and controllers are safety agency-approved components, so

certification of your system is easier

y High Resolution and Accuracy

Disadvantages of Resistive

y 80 % Clarity

y Resistive layers can be damaged by a sharp object


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2.Surface Acoustic Wave Touch Screens

The SAW touch screen is a glass overlay with transmitting and receiving

piezoelectric transducers for both the X and Y-axes. The touch screen controller

sends a 5 MHz electrical signal to the transmitting transducer, which converts the

signal into surface waves. These mechanical waves are directed across the opposite

side gather and direct the waves to the receiving transducer, which reconverts them

into an electrical signal.

Surface Acoustic Wave Touch Screens

When the front surface of the touch screen is touched, a portion of the mechanical

wave is absorbed, thus changing the received signal. The signal is then compared to

a stored reference signal, the change recognized, and a coordinate calculated. This

process happens independently for both the X and Y-axes. By measuring the

amount of the signal that is absorbed, a Z-axis is determined.


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Acoustic wave touch screens have transducers that emit ultrasonic sound waves

along two sides. Guided acoustic wave (GAW) systems function by the

transmission of an acoustic wave through a glass overlay on a display surface, and

surface acoustic wave systems (SAW) function by the transmission of an acoustic

wave over a glass overlay on a display surface.When an input device, such as a

finger, dampens the wave, electronic sensors determine the location of the

dampened area, recognizing a touch. SAW touch screen monitors have significant

stylus limitations. A stylus is the actual device, which touches the displays screen.

These systems require a soft, energy absorbing pressure that would come from a

finger. Although the human finger is the most popular stylus, often it is desirable

to have a pen-based stylus so the display does not become dirty. In this case, if

trying to use a pen, the acoustic wave would not be dampened and no touch

would be recognized.

Advantages of Surface Acoustic Wavey Excellent Image Clarity

y Very High Light Transmission

y Excellent Durability

y Stable "No-Drift" Operation

y High Resolution


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y Finger or Gloved-Hand Operation

y Very Light Touch

y Fast Touch Response

y X-, Y-, and Z-axis Response

y Overlay That Can Be Antiglare-Treated

Disadvantages of Surface Acoustic Wave

y Must be touched by finger, gloved hand, or soft-tip stylus.

y Something hard like a pen won't work

y Not completely sealable, can be affected by large amounts of grease,

water, or dirt on the touch screen

3.Capacitive Touch Screens

A capacitive touch screen panel is coated with a material, typically indium tin

oxide that conducts a continuous electrical current across the sensor. The sensor

therefore exhibits a precisely controlled field of stored electrons in both the

horizontal and vertical axes - it achieves capacitance.


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As the human body is also a conductor, touching the surface of the screen results

in a distortion of the local electrostatic field, measurable as a change in

capacitance. Different technologies may be used to determine the location of the

touch.

When the sensor's 'normal' capacitance field (its reference state) is altered by

another capacitance field, i.e., someone's finger, electronic circuits located at

each corner of the panel measure the resultant 'distortion' in the sine wave

characteristics of the reference field and sends the information about the event

to the controller for mathematical processing. Capacitive sensors can either be

touched with a bare finger or with a conductive device being held by a bare hand.

Capacitive touch screens are not affected by outside elements and have high

clarity.

The Apple iPhone is an example of a product that uses capacitance touch screen

technology. The iPhone is further capable of multi-touch sensing.

Capacitive sensors work based on proximity, and do not have to be directly

touched to be triggered. In most cases, direct contact to a conductive metal


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surface does not occur and the conductive sensor is separated from the user's

body by an insulating glass or plastic layer. Devices with capacitive buttons

intended to be touched by a finger can often be triggered by quickly waving the

palm of the hand close to the surface without touching.

Advantages of Capacitive

y High Touch Resolution

y High Clarity

y Completely Seal able

Disadvantages of Capacitive

y Must be touched by finger- will not work with any non-conductive input

y Can be affected by electricity

y May need re-calibration often

4.Infrared

Conventional optical-touch systems use an array of infrared (IR) light-emittingdiodes (LEDs) on two adjacent bezel edges of a display, with photosensors placed

on the two opposite bezel edges to analyze the system and determine a touch

event. The LED and photosensor pairs create a grid of light beams across the

display. An object (such as a finger or pen) that touches the screen interrupts the

light beams, causing a measured decrease in light at the corresponding

photosensors. The measured photosensor outputs can be used to locate


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atouchpoint coordinate.

Widespread adoption of infrared touchscreens has been hampered by two

factors: the relatively high cost of the technology compared to competing touch

technologies and the issue of performance in bright ambient light. This latter

problem is a result of background light increasing the noise floor at the optical

sensor, sometimes to such a degree that the touchscreens LED light cannot be

detected at all, causing a temporary failure of the touch screen. This is most

pronounced in direct sunlight conditions where the sun has a very high energy

distribution in the infrared region.

However, certain features of infrared touch remain desirable and represent

attributes of the ideal touchscreen, including the option to eliminate the glass or

plastic overlay that most other touch technologies require in front of the display.

In many cases, this overlay is coated with an electrically conducting transparent

material such as ITO, which reduces the optical quality of the display. This

advantage of optical touchscreens is extremely important for many device and

display vendors since devices are often sold on the perceived quality of the user

display experience.

Another feature of infrared touch which has been long desired is the digital


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nature of the sensor output when compared to many other touch systems that

rely on analog-signal processing to determine a touch position. These competing

analog systems normally require continual re-calibration, have complex signal-

processing demands (which adds cost and power consumption), demonstrate

reduced accuracy and precision compared to a digital system, and have longer-

term system-failure modes due to the operating environment.

5.Optical imaging

A relatively-modern development in touchscreen technology, two or more image

sensors are placed around the edges (mostly 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 or even measure the size of the touching object

(see visual hull). This technology is growing in popularity, due to its scalability,

versatility, and affordability, especially for larger units.

Introduced in 2002 by 3M, this system uses sensors to detect the mechanical

energy in the glass that occurs due to a touch. Complex algorithms then interpret

this information and provide the actual location of the touch. The technologyclaims 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 stylus. A downside is that after the initial touch the system cannot detect a

motionless finger.

6.Acoustic pulse recognition

Acoustic pulse recognition system uses more than two piezoelectric transducers

located at some positions of the screen to turn the mechanical energy of a touch

(vibration) into an electronic signal. This signal is then converted into an audio


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file, and then compared to preexisting audio profile for every position on the

screen. This system works without a grid of wires running through the screen; the

touch screen itself is actually pure glass, giving it the optics and durability of the

glass out of which it is made. It works with scratches and dust on the screen, and

accuracy is very good. It does not need a conductive object to activate it. It is a

major advantage for larger displays. As with the Dispersive Signal Technology

system, after the initial touch this system cannot detect a motionless finger.

Frustrated total internal reflection

This optical system works by using the principle of total internal reflection to fill a

refractive medium with light. When a finger or other soft object is pressed against

the surface, the internal reflection light path is interrupted, making the light

reflect outside of the medium and thus visible to a camera behind the medium.

Latest development

Introducing a New Touch Screen System

Touch screens are widely used in numerous industries and applications that require

exacting combinations of accuracy, touch sensitivity, and durability. Each touch

screen application has its own unique challenges, and traditionally, customers

choose the touch screen technology with the fewest disadvantages and technical

limitations for their specific application. Enter Dynapros Near Field Imaging

(NFI) Touch Screen System. Patented by Dynapro in 1997, it is uncompromising

in both performance and toughness, making it the perfect choice when high clarity

and durability are at issue.


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What is NFI?

Simply put, its a touch screen where the screen itself is the sensor. NFI uses a

sophisticated sensing circuit that can detect a conductive object - a finger or

conductive stylus - through a layer of glass, as well as through gloves or other

potential barriers (moisture, gels, paints, etc.). This is achieved with a high degree

of accuracy using data acquisition and image processing techniques that generate a

precise profile of the touch.

The NFI touch screen sensor uses a transparent conductive film patterned with a

proprietary topology applied to the base layer of glass. The front layer of glass is

bonded over the base layer with an optical adhesive. An excitation waveform is

supplied to the conductive layer by the controller to generate a low strength

electrostatic field in the front layer of glass. The near field is modulated by finger

contact with the front layer of glass, and a resultant differential signal is created,

making it possible to accurately resolve the electrostatic loading on the face of the

screen.

Dynapros dataacquisition expertise was instrumental in designing the method by

which the system firmware recognizes and decodes the location of the touch. The

controller scans continuously until it receives signs of an impending touch. At this

point it shifts into a different mode and subtracts the baseline associated with the

conditions immediately preceding the touch. This way, static and noise do not

affect the image of the touch. The profile of the touch is constructed from a

dynamic array of data points, and resolved to an actual touch point through

continuous re-imaging of the electrostatic field. Touch coordinates are fed back to

the operating system as fully compliant Microsoft mouse coordinates.

Once a touch is registered, its effect is zeroed out, so a subsequent touch in another

location can be detected. The system resolves and reports concurrent touches


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without averaging, allowing for advanced touch input capabilities.

Any long-term changes in the electrostatic image are compensated for, allowing

the system to ignore unwanted objects directly on the screen such as water

droplets, insects, conductive dirt, or other adhering contamination. Imaging also

enables the touch screen to ignore unwanted loading effects from large or distant

objects such as hands or arms, and to reject false touches.

Sophisticated data acquisition and image processing ensure NFI is accurate enough

to control equipment consistently and precisely, yet sensitive enough to detect

finger touches through gloves, and work through moisture and other contaminants.

The sensors glass construction provides superior optical performance, and will

continue to operate despite scratching, pitting, and other surface damage from

abrasives, chemicals or vandals.

NFI touch screens can be reliably sealed for applications that require high pressure

washdown or protection from contaminant-filled environments.

NFI Addresses Needs

NFI offers significant advantages in performance and durability without

compromises, and its the only touch screen technology that overcomes the

technical limitations found in other touch screen technologies, by addressing three

main factors:

* Accuracy - the ability to control equipment consistently and precisely

despite extreme environmental conditions

* Touch Sensitivity - the ability to operate the touch screen with gloves

through moisture, dirt, and other surface contaminants


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* Durability - the ability to withstand scratches and other surface damage

caused by abrasives, chemicals, or vandalism

The Benefits of NFI

Designed for Ruggedness

NFI technology offers protection against scratches, scrapes, gouges, and severe

abrasion. The sensor layer of the screen is well protected beneath the glass surface,

so performance remains unaffected even if the front glass layer is damaged.

Contaminant Proof


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Surface contaminants such as moisture, dirt, grease, and chemicals do not affect

the performance of the touch screen and can easily be cleaned. The touch screen

stands up to virtually all chemicals and continues to function accurately through

any sub-stance.

Touch Sensitivity

You can activate NFI with a touch of a finger - gloved or ungloved - or other

conductive stylus.

Stability

Variations in temperature, humidity, and altitude do not affect NFI. The touch

screen remains drift-free and does not require field calibration to maintain

accuracy. NFI is also immune to electro-static discharge and electromagnetic

interference.

Sealing CapabilityNFI touch screens can be reliably sealed for applications that require high pressure

washdown or for protection from contaminant-filled environments. Systems

incorporating NFI touch screens can readily achieve a NEMA 4X rating.

Performance

NFI requires very light contact and responds instantly to an operators touch. With

NFIs linearity and resolution, you can effectively perform drag and drop

operations. And the NFI touch screen also resolves and reports concurrent touches

without averaging.


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Shockand Vibration

NFI touch screens can withstand significant vibration and shock without

jeopardizing safety or performance. With chemically strengthened glass and no

mechanically sensitive components, NFI performs reliably when used in a high

vibration environment.

Optical Clarity

NFIs solid glass layer provides excellent image clarity. With extremely high

transmissivity, and unobtrusive glare and reflection protection, NFI provides aclear window for any application.

How is Touch Technology different from

other devices?

No special commands to learn.

The user doesn't need to look away from the screen to a keyboard and

back again.

Entering wrong information is impossible, only valid options are

offered on the screen.

There are no loose pieces of hardware to be damaged or lost


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Application of Touch screen

The touch screen is one of the easiest PC interfaces to use, making it the interface

of choice for a wide variety of applications. Here are a few examples of how touch

input systems are being used today:

Public Information Displays

Information kiosks, tourism displays, many people that have little or

no computing experience use trade show displays, and other electronic

displays. The user-friendly touch screen interface can be less

intimidating and easier to use than other input devices, especially for

novice users. A touch screen can help make your information more

easily accessible by allowing users to navigate your presentation by

simply touching the display screen.

Retail and Restaurant Systems

Time is money, especially in a fast paced retail or restaurant

environment. Touch screen systems are easy to use so employees can


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get work done faster, and training time can be reduced for new

employees. And because input is done right on the screen, valuable

counter space can be saved. Touch screens can be used in cash

registers, order entry stations, seating and reservation systems, and

more.

Customer Self-Service

In todaysfast pace world, waiting in line is one of the things that have

yet to speed up. Self-service touch screen terminals can be used to

improve customer service at busy stores, fast service restaurants,

transportation hubs, and more. Customers can quickly place their own

orders or check themselves in or out, saving them time, and

decreasing wait times for other customers. Automated bank teller

(ATM) and airline e-ticket terminals are examples of self-service

stations that can benefit from touch screen input.

Control and Automation Systems

The touch screen interface is useful in systems ranging from industrial

process control to home automation. By integrating the input device

with the display, valuable workspace can be saved. And with a

graphical interface, operators can monitor and control complex

operations in real-time by simply touching the screen.


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Computer Based Training

B

ecause the touch screen interface is more user-friendly than otherinput devices, overall training time for computer novices, and

therefore training expense, can be reduced. It can also help to make

learning more fun and interactive, which can lead to a more beneficial

training experience for both students and educators.

Assistive Technology

The touch screen interface can be beneficial to those that have

difficulty using other input devices such as a mouse or keyboard.

When used in conjunction with software such as on-screen keyboards,

or other assistive technology, they can help make computing resources

more available to people that have difficulty using computers.

And manymore uses...

The touch screen interface is being used in a wide variety of

applications to improve human-computer interaction. Other

applications include digital jukeboxes, computerized gaming, student

registration systems, multimedia software, financial and scientific

applications, and more.


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References:

http://www.touchscreen_encyclopedia.com

http://www.elotouchsystem.com

http://www.seminarprojects.com

http://Touchscreens.com

http://Abilityhuh.com

http://Webopedia.com/Touchscreen

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