Hardware Devices Input

Hardware Devices Input

1. Mouse

   • X-Y position indicator for a display system
   • detects movment in two axes
   • buttons click on the Graphical User Interphase (GUI) components

2. Keyboard

   • used to enter text into a computer
   • keys are continually scanned to detect pressing for keys and key combinations
   • the key/combination scan code is sent to the computer
   • the computer converts the scan code into an ASCII/Unicode code

3. Bar Code Reader

   • A Bar Code: a sequence of black and white bars that encodes information such as the product identifier
     • the product identifier is usually printed legibly below
   • Light Source, Lens, Photoelectric detectors
     • White bands reflect more light than dark bands
     • electrical form of bar code is analysed and decoded as character code
   • reads printed bar codes on goods

4. Scanners

   • Fingerprint scanner
     • picture of ridges and valleys of fingerprint is taken and analysed
     • some use light, others use electrical currents
     • authenticate user logins on many devices e.g. laptops and phones
   • Iris scanner
     • Iris: Flat coloured disk of the eye
     • uses infrared light o store a image of the iris electronically from max 3ft away
     • code of typically 512 bytes is created from the scan
     • enough random variation in iris patterns to distinguish reliable between individuals
   • Retina scanner
     • low-energy infrared scans retina of eye to produce an encoded form of the retina pattern
     • blood vessels absorb more light than surrounding tissue
     • retina is unique and hardly changes in life
   • Optical mark reader
     • used to detect markings in set positions, which may or may not be present e.g. pencil line answers on a multiple choice paper or lottery tickets
   • Optical character reader (OCR)
     • analyses images of text to recognise the characters
     • used to automate postal sorting by reading postcodes then making the post with phosphor dots for further machine reading
   • Flatbed scanner
     • Glass plane/platen
     • illuminated from below by a bright light bulb
       • Xenon or cold cathode fluorescent
     • light detecting sensors along width of platen are moved slowly across the length of the plane with the light source
       • Three rows of R,G andB sensors
     • reflected light is converted into an electrical equivalent
     • digitised image is created of the entire scan which is stored and processed by the attached computer
     • (an opaque cover excludes ambient light)
   • sensor and decoder

5. Magnetic Strip Reader

   • reads magnetically encoded information on a plastic or cardboard card
   • orientation of the particles in the strip is used to encode binary data
   • 2KB of data can be stored on a strip
   • used in credit cards, membership cards, railway tickets, bus tickets, phone cards and hotel keys
   • replaced in favour of smart cards

6. RFID Reader

   • R.ADIO F.REQUENCY I.D.ENTIFICATION
   • Transmits data, clock and energy a via radio frequencies from a transponder to the receiver/reader
   • stores a few bytes -> kilobytes
   • contactless security devices for identification
     • radio tags on pets
     • oyster cards
     • skipasses

7. Smart Card Reader

   • Smart Cards: contain an integrated circuit chip
     • replacing magnetic strip cards
     • micro procesor
     • ROM
     • EEPROM
     • RAM
     • Computer Bus System
     • smart cards can encrypt and decrypt data so can protect against fraud
   • Powers the integrated circuit chip
   • used incredit cards, membership cards, railway tickets e.g. Oyster Cards, bus tickets, phone cards and hotel keys

8. Touch Screen

   • VDU and IO
   • region just infront of screen has light beams and sensors which are tripped
     • coordinates are electronically deciphered and mapped
       • mapping results in actions

9. Graphics Tablets

   • drawings are input electronically to a computer
   • Stylus and tablet
     • pressing the tip of the stylus to the tablet operates a microswitch and the movement is recorded
     • pointing and clicking can be analysed as commands
     • the tablet contains electronics to detect location of the stylus
   • Puck and tablet
     • cross hairs on the lens of the puck are aligned to a line drawing and recorded

10. Voice Recognition

    • A computer is trained to recognise a person's voice to turn speech into text
    • Microphone, Sound card, software

11. Digital Still Camera

    • captures and stored photographs digitally on a memory card before upload to a computer
    • can record sound and video too
    • charge coupled devices CCD
    • CMOS image sensor

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