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					       AS Level ICT

Selection and use of output methods,
    media, and devices: Printers
                Output methods
• Outputs come in a variety of different formats
  including:
   – Hard copy (e.g. paper printouts)
   – On-screen display (e.g. webpage)
   – Digital outputs as inputs (e.g. a weather station’s
     output is sent in digital form to the National
     Weather Centre’s computer, where it becomes
     part of the inputs the computer needs to track
     and predict the national weather picture)
            Output methods
– Digital outputs to portable devices (e.g. files
  saved from a computer onto an IPod or MP3
  player)
– Digital outputs as control signals (e.g. computer
  aided manufacture)
              Output devices
• Outputs devices include:
  – Printers
  – Screens (also called Visual Display Units)
  – Plotters
  – Speakers and headphones
  – Any device that produces output media (e.g.
    Flash drives, removable hard drives, CD-ROMs,
    CD-RW, DVDs)
                     Printers
• The main types of printers are:
   – Ink-jet printers
   – Laser printers
   – Dot matrix printers
   – Thermal printers
   – Multifunctional printer
                Ink-jet printers
• Ink-jet printers are popular with home and small
  office users
• They work by spraying dots of fast-drying ink onto
  paper, and can produce both colour and black and
  white printouts
                Ink-jet printers
• The dots are extremely small (usually between 50
  and 60 microns in diameter, which is smaller than
  the diameter of a human hair [70 microns])
• The dots are positioned very precisely, with
  resolutions of up to 1440 x 720 dots per inch (dpi)
• The dots can combine different colours together to
  create photo-quality images
                Ink-jet printers
• The main components of an ink-jet printer are:
   – The print head assembly
      • Print head – contains a series of nozzles that
        are used to spray drops of ink
      • Ink cartridge – this contains the ink that is
        sprayed through the print head
      • Print head stepper motor – moves the print
        head assembly (print head and ink cartridges)
        back and forth across the paper
         Ink-jet printers




Print head             Stepper motor
           Ink-jet printers
• Belt – is used to attach the print head
  assembly to the stepper motor
• Stabiliser bar – is used to ensure that
  movement is precise and controlled
 Ink-jet printers




Stabiliser bar and belt
             Ink-jet printers
– The paper feed assembly
   • Paper tray feeder
   • Rollers – pulls the paper from the paper tray
     feeder and advances it when the print head
     assembly is ready for another pass
   • Paper feed stepper motor - powers the rollers
     to move the paper in the exact amount
     needed to produce a continuous image
– Power supply
– Control circuitry
– Interface ports
Ink-jet printers




     Rollers
      Ink-jet printers - Advantages
• Ink-jet printers:
   – Can produce high quality printouts (including
     photographs)
   – Are quiet when operating
   – Are cheap to buy
    Ink-jet printers - Disadvantages
• Ink-jet printers:
   – Are costly to run (ink cartridges are expensive
     and the cost per page is higher than a laser
     printer)
   – Can produce smudged images (the ink used will
     smudge if the printout is not handled properly,
     especially just after printing)
   – Need special paper when producing
     photographic images
                Laser printers
• Laser printers are popular with business users
• They work by using photocopier technology and
  toner to produce printed outputs
Laser printers
Laser printers
     Static electricity is what
     makes a laser printer work
     Static electricity is an
     electrical charge that builds
     up on an insulated object
     Because oppositely charged
     atoms are attracted to each
     other, objects with opposite
     static electricity fields cling
     together
Laser printers
     A laser printer uses this
     phenomenon as a sort of
     "temporary glue"
     The core component of this
     system is the photoreceptor,
     which is usually a revolving
     drum or cylinder
     This drum assembly is made
     out of highly photoconductive
     material that is discharged by
     light photons
Laser printers
     Initially the drum is given a
     positive charge by the
     charge corona wire
     This is a wire with an
     electrical current running
     through it
     As the drum revolves, the
     printer shines a tiny laser
     beam across the surface to
     discharge the charge at
     certain points
Laser printers
     In this way, the laser "draws"
     the letters and images to be
     printed as a pattern of
     electrical charges – an
     electrostatic image
     The system can also work
     with the charges reversed –
     that is, a positive
     electrostatic image on a
     negative background
Laser printers
     Once the pattern is set, the
     printer coats the drum with
     positively charged toner
     Since it has a positive
     charge, the toner clings to
     the negative discharged
     areas of the drum, but not to
     the positively charged
     "background"
Laser printers
     With the powder pattern on
     the drum, it rolls over the
     paper, which is moving along
     a belt below
     Before the paper rolls under
     the drum, it is given a
     negative charge by the
     transfer corona wire
     (charged roller)
Laser printers
     Because this charge is
     stronger than the negative
     charge of the electrostatic
     image, the paper pulls the
     toner powder away from the
     drum
     Since it is moving at the
     same speed as the drum, the
     paper picks up the image
     pattern exactly
Laser printers
     To keep the paper from
     clinging to the drum, it is
     discharged by the detac
     corona wire immediately
     after picking up the toner
Laser printers
     The printer then passes the
     paper through the fuser
     The fuser is a pair of heated
     rollers
     As the paper passes through
     these rollers, the loose toner
     powder melts, fusing with the
     fibres in the paper
     The fuser rolls the paper to
     the output tray
Laser printers
      Laser printers - Advantages
• Laser printers:
   – Have a high print speed, which makes them very
     useful in an office environment
   – Are very reliable
   – Have a low print cost per page when printing in
     black and white
   – Use standard paper
   – Are quiet when operating
    Laser printers - Disadvantages
• Laser printers:
   – Have a high initial start-up cost
   – Use more electrical power than other printers
   – Have a high print cost per page when printing in
     colour
              Dot matrix printers
• Dot matrix printers were – at one time – very
  common, but now they are rarely found outside
  certain specialist business environments
• They are also know as impact printers because
  they work by hitting a matrix of small pins against
  an ink-impregnated ribbon
Dot matrix printers
             Dot matrix printers
• The matrix of pins form the characters, and when
  the ribbon is pushed against the paper by the
  impact, the characters are printed
Dot matrix printers




 Dot matrix printer head
    Dot matrix printers - Advantages
• The dot matrix printer has several unique
  advantages over other printers including:
   – Their ability to print multi-part forms using NCR
     (no carbon required) paper; this enables several
     copies of the same form to be printed so that
     they can be distributed to different parts of an
     organisation
   – Their ability to print on continuous stationery –
     the sprocket feed enables continuous (and often
     NCR) stationery to be used; this is particularly
     useful when printing product lists, stock lists, etc.
  Dot matrix printers - Advantages




Continuous feed paper

                        NCR (no carbon
                        required) forms
Dot matrix printers - Advantages
– Their reliability because they use simple
  technology that rarely fails
– Their ability to switch between different paper
  sources
 Dot matrix printers - Disadvantages
• The dot matrix printer has several disadvantages:
   – They are very noisy
   – The characters that are printed are unclear
     because they are a matrix of dots and not a
     completely formed character
   – They cannot produce graphical images
   – They can only print in the colour of the ribbon
     that has been installed in the printer
              Thermal printers
• Thermal printers are popular with users who need
  fast, silent, and high quality output
• They are used in:
   – Cash registers and point-of-sale terminals
   – Cark park ticket printers
   – Lottery ticket printers
Thermal printers
         Multifunctional printers

• Multifunctional printers (often called PSCs
  [printer/scanner/copiers]) are very popular in
  environments (e.g. home offices, small
  offices) where space or specialist usage are
  limited
          Multifunctional printers

• They combine several related information
  communication technologies into one
  machine:
   – Printer (usually either an ink-jet or laser
     printer)
   – Scanner
   – Photocopier
   – Fax machine
Multifunctional printers
       AS Level ICT

Selection and use of output methods,
    media, and devices: Printers

				
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