Document Sample
Unit2 Powered By Docstoc
					By the end of this Unit you should be able to:

   Explain the term input device

   Explain the features of the following input devices:

   Basic, Braille, Concept, Ergonomic and Wireless keyboards
   Mouse – standard, optical and cordless
   Digital camera
   Digital video camera
   Sound card
   Touch sensitive screen
   Graphics Tablet/Digitising Tablet/Digitiser
   Light pen
   Optical Mark Reader
   Bar Code Reader
   Magnetic Ink Character Recognition Reader
   Magnetic Stripe Reader
   Musical Instrument Digital Interface (MIDI)
   Voice/Speech Recognition
   Handwriting Recognition

                                       Page 10
Computer Systems

Unit 2

Input Devices

These let you enter data, commands and programs into the computer’s Central
Processing Unit (CPU):

Traditional Keyboard

The keyboard is made up of lots of keys that, when they
are pressed, they cause a certain signal to be sent to the
computer. This signal tells the computer which key on the
keyboard has been pressed. A keyboard is the most
common form of input device.

Figure 1 – Typical traditional computer keyboard

Braille keyboard

People who are visually impaired use Braille code. This consists of letters and symbols
that are read by fingers moving across a series of raised dots. To
enter data, the Braille note taker can be plugged directly into a

                Figure 2 – Braille keyboard - braillekeyboard.html

Concept (touch sensitive) keyboard

This is a flat panel of contact switches covered by a flexible membrane. Each switch
can be programmed to respond in different ways by the computer
software. Overlays with pictures and symbols are placed over the
membrane. Concept keyboards can be found in primary schools
where young children can simply press on the symbols and pictures
on the overlay. They are also used in restaurants where the
checkout tills use symbols to speed up data entry.

Figure 3 – Concept keyboard - conceptkb.html

                                       Page 11
Ergonomic keyboard

These have been developed to reduce the
risk of repetitive strain injury (RSI) to
workers who use keyboards for long periods
of time. Keys rely on finger pressure rather
than hand movement and the keyboard has
been split into 2 sections so that the user’s
wrists are in a more natural and comfortable

                                  Figure 4 – Ergonomic keyboard –

Wireless Optical Keyboard

The Wireless Optical Keyboard and mouse works with Microsoft’s Transceiver for
                                     Bluetooth, providing a wireless range of up to 30
                                     feet (January 2004). The keyboard is not only
                                     sleek and ergonomically designed, but will give
                                     you forward and back internet buttons, scroll
                                     wheel, detachable palm rest, programmable Hot
                                     Keys, one-touch multimedia keys, and the power
                                     of optical technology.
Figure 5 – Wireless Optical Keyboard –

Standard Mouse

This is a simple input device that is used along with a keyboard.
The mouse moves an arrow or pointer around the screen. As the
mouse moves around the top of the desk, the arrow on the screen
moves also. You use the mouse to point to things on the screen and
then select them using one of the buttons on the top of the mouse.
A mouse is often used with graphical data such as drawings or
graphics on screen.

             Figure 6 – Standard two-button mouse –

                                       Page 12
Optical Mouse

Here the rubber ball has been replaced with an optical sensor that
detects motion on the desktop. A tiny digital camera takes
pictures of the surface beneath the mouse and these pictures are
translated into movement of the cursor on the screen.

                 Figure 7 – Optical mouse -

Optical Cordless Mouse

The optical cordless mouse features the Tilt Wheel Technology, and wireless technology
                       so you can roll and scroll free of clutter. The mouse relies on
                       digital radio technology to send signals to a digital receiver.
                       Radio waves enable communication with the Central Processing
                       Unit from a distance of up to 2 metres regardless of anything
                       that might be in the way.

Figure 8 – Optical cordless mouse –


A trackball is really like an upside down mouse. Instead of moving the
mouse around the desktop, you move a little ball that is inside a casing.
You move the ball using the palm of your hand or your thumb. When the
ball is moved, the pointer moves across the screen.

Like a mouse, a trackball is often used with graphical data such as
drawings or graphics on screen. Many laptop computers used a trackball
because it takes up less space than a mouse.

                        Figure 9 – Three-button trackball -

                                        Page 13

                     Figure 10 – Trackpad/Touchpad -

Found on notebook computers and offer the same functions as the mouse. Moving your
finger across the pad controls the movement of the pointer on the screen. Tapping
lightly on the pad has the same function as clicking the mouse button.


The microphone is a sensor (an input device used for measuring a physical quantity) that
detects sound. Microphones are used by people who are severely
handicapped or where the user needs to keep his/her hands free to do
other things. They may be used with voice recognition software (more
later) to translate spoken words into digital signals for the computer. The
computer will match the voice pattern with those stored in the system.

         Figure 11 – microphone - scoop/interviews/


This is a popular input device for computer games. The hand grip can be moved around
the central axis in any direction but is spring-loaded to return to the centre when the
hand pressure is released. Joysticks have buttons to control the software functions.
                                           For example, when using a joystick to control a
                                           flight simulator, the buttons control the flaps,
                                           views from the cockpit, landing gear and engine
                                           speed. Some joysticks have ‘force feedback’
                                           buttons which enables the user to feel some of
                                           the forces that might be experienced in real
                                          Figure 12 – Joystick –

                                        Page 14
Digital Camera

The picture taken with the digital camera is stored in computer memory rather than on
film. The different colours that make up the picture are converted to digital signals (0s
and 1s) by sensors placed behind the lens. The pictures can be displayed on your
computer monitor, on the digital camera’s LCD screen (if it has one), imported into a
graphics/art program for editing or printed (using an ink-jet printer and high quality
paper). The quality of the picture is determined
by the resolution of the camera and is measured in
pixels (the greater the number of pixels, the
sharper the image). High quality digital cameras
have a resolution of 4 or more megapixels.

Figure 13 – Digital Camera –

Digital Video Camera (Camcorder)

These plug straight into the computer using a Firewire connection (a very fast data link
to the computer). This allows the computer to download, store and manipulate the
digital video images. Video capture and editing requires large amounts of computer
memory so computers need to have
large hard disk drives to hold these

Figure 14 – Digital Video Camera


The webcam (world wide web camera) is a digit camera that sits on or by a
computer. The webcam will automatically record an image every so often
(seconds, minutes or even hours) rather than continuously. The image is
then viewed through a web page. The quality of the lenses and the
resolution of web cams are less than the more expensive digital cameras.

                 Figure 15 – Webcam - webcam.jpg

                                       Page 15

              Most computers are fitted with a small internal speaker that will beep to
              draw your attention to an error. Multimedia computers, like the ones in
              school, may have additional speakers attached to the computer to provide
              better quality sound.

Figure 16 – Computer Speakers - computers.html

Sound Card

                     A sound card enables the computer to output sound through the
                     speakers. The Sound Blaster Sound Card has become the standard
                     for most PCs.

Figure 17 – a Sound Card –

                Figure 18 – The Sound Blaster Sound Card kit -


A scanner is used to take information stored on paper and read it into a computer
system. Scanners can be used to convert photographs, paintings and typed text into a
form that can be stored in a computer. Scanning text in order to recognise the words
and letters require special software called Optical Character Recognition (OCR – the
software identifies written or printed characters individually and converts them to their
digital equivalent. It is not perfect – some letters may be misread – careful proof-
reading is therefore needed).

                                                                           Figure 19 – A
                                                                            Scanner and
                                                                        Flatbed Scanner

                                       Page 16
There are 2 types of scanners:

Flatbed scanners read documents placed face down on them like a photocopier. A
sensor moves across (scans) beneath the glass reading the words, symbols and graphics
as a pattern of light and dark or colour, which it then translates into a digital signal that
the computer can store and manipulate. The image is then displayed on screen. The user
can then resize it, change its colour or remove any imperfections. The quality of the
image depends on the resolution of the scanner – the higher the resolution, the sharper
and clearer the image.

Hand-held scanners are a lot smaller than flatbed scanners, often only a few
centimetres wide. The scanner reads documents by rolling the scanner across them.
The image produced is of a poorer quality to that produced by a flatbed scanner.

Touch sensitive screen

This is a type of display screen that has a touch-sensitive panel
covering the screen. There are criss-crossing beams of infra-red
light in front of the glass on the monitor. When the user touches
the glass with their finger, 2 sets of rays are blocked, the rays
travelling from side to side and the rays going from top to bottom.
The computer detects the finger’s position from the light sensors
placed on the opposite side of the monitor screen to the light

                                                   Figure 20 – Touch Sensitive Screen -

Touch-screens are user-friendly and can be used to access the internet, send emails or
choose ring tones from your mobile phone. They are found in public places like museums.

Although they provide a natural way for users to act with computers, they are
unsatisfactory for most applications because the finger is really too big for this task. It
is impossible to point accurately to small areas of the screen. Also most users find touch
screens tiring to the arms after long use.

                                        Page 17
Graphics Tablet/Digitising Tablet/Digitiser

This is a flat pad which the user can write or draw on with a device
similar to a pen. This device is called a Stylus. The surface of the
pad is sensitive to the position of the stylus and the stylus itself is
sensitive to the pressure applied by the user. As the stylus is
moved across the pad, the movement is translated to a drawing on
the computer monitor. The harder the user presses on the stylus,
the thicker the line drawn on the screen.

                                                               Figure 21 – Graphics Tablet

Light pen

A light pen is a pen-shaped device connected to the computer with a cable. It has a light
detector in the tip of the pen that picks up the light signals from the monitor. You can
use the pen to select menus, activate programs and draw lines on
the screen.

A light pen is often used along with a drawing package. The user
touches the pen against the screen and then moves the pen
around. As the pen moves, the computer draws a line where the
pen has just been. This means the user can use a light pen to
create graphics.

                                              Figure 22 – Light pen -

Sensors are used to detect environmental conditions such as temperature, light,
humidity and pressure in computerised control systems. An electronic signal is used to
register the current condition and a signal sent to the computer. Sensors are used in
heating systems – a sensor is used to measure the temperature. When
the temperature falls below a pre-set level, the computer will react by
producing a signal to the heater to bring the temperature back up to
the pre-set level. When that temperature is reached the computer will
send an instruction to the heater to switch the heater off.

               Figure 23 – Heating Sensor - eib_heatcontrol.jsp

                                         Page 18
Sensors are also used to gather data which is then stored on the
computer. This is called data logging. Eg sensors will record daily
temperatures, hours of sunshine etc and will log that data in order to
produce weather statistics.

     Figure 24 – Rainfall Sensor-
Optical Mark Reader (OMR)

                    This is a scanning device that reads marks made with a soft pencil
                    or black pen made on paper.

                    Figure 25 – Optical Mark Reader -

Optical Mark Readers are used for inputting the numbers on the
lottery tickets and can also be used for recording the answers on
multiple-choice examination papers, for school registers and for
recording gas and electricity meter readings. The reader scans
across the paper with an infra-red light. Where there is no mark,
there is a strong reflection of light off the white paper, where a
mark has been made, the light reflection is reduced and this is input
to the computer.
                Figure 26 – National Lottery ticket printed by lottery ticket terminal

Bar Code Reader

Bar codes are made up of black and white stripes of different thicknesses. The lines
                represent numbers and are read with a wand or laser scanner. The bar
                code numbers hold coded information about the product, including the
                country of manufacture, the manufacturer’s name, product item code
                and a check digit. When the bar code is scanned, the data is passed to
                the computer which then returns information about the product.
                 Figure 27 – Bar code -

Figure 28 – Bar Code Reader -

                                       Page 19

Magnetic Ink Character Recognition (MICR)

                Used on bank cheques. The important data on a bank cheque (bank sort
                code number, account number, cheque number) is printed along the
                bottom edge of the cheque as strange looking characters. The ink used
                to form these characters contains tiny magnetic particles that enable
                the data from each cheque to be read into the computer by machine.
                Figure 29 – MICR Reader -

Magnetic Stripe Reader

Many of us carry cards (bank cards, swipe cards, library cards, train
tickets) which have a magnetic stripe on one side (usually the back of the
card). Information about your account is magnetically stored on the black
stripe and when you swipe the card the stored information is read by the
Magnetic Stripe Reader and input to the computer system.

      Figure 30 – Magnetic Stripe Reader - html/magnetic.htm

Musical Instrument Digital Interface (MIDI)

                     Figure 31 – Musical Instrument Digital Interface -

Computers fitted with MIDI interface boards can be connected to MIDI instruments
(allowing music to be input to and output from the computer). Software on the computer
enables the music to be stored, displayed on the monitor as a musical score and edited
by adding, deleting and moving notes. Music from different instruments can be added as
new tracks so that one musician can create the effect of a
whole orchestra.

Figure 32 – Musical Instrument Digital Interface - accord34.htm

                                      Page 20

Voice/Speech Recognition

With voice recognition systems, the computer can recognise the words spoken to it and
can carry out commands associated with the words. Using voice recognition, a letter can
be dictated (spoken) instead of being typed at the keyboard. This software ensures
that people with disabilities (RSI, Dyslexia, Stroke, Cerebral Palsy, Loss of Limbs,
partially and non-sighted) have a computing solution to take them
forward. However, many systems need the speaker to speak slowly
and distinctly, thus restricting their use to a few specialised
situations. Recently, though great strides have been made in voice
recognition systems that allow the user to speak naturally. There
are now several systems like this available for personal computers.
As computer systems cost less and increase in power, speech
recognition is being used as an alternative to the keyboard.

Figure 33 – Voice Recognition -

Handwriting Recognition

Using only your PC, a microphone and/or Graphics Tablet and special handwriting
recognition software, your computer can recognise your handwriting in minutes. This
helps us to write and draw in a more natural way.

However, this technology is still very young and is not as fast or as accurate as it needs
to be for successful use. Another reason for its slow
acceptance is that the keyboard is in fact more convenient
in many situations. Many people can type with a keyboard
much faster than they can write by hand.

                    Figure 34 – Handwriting Recognition - 03may28hanrec.asp

                                        Page 21

Shared By: