AS Level ICT

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AS Level ICT

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

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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
  stations output is sent in digital form to the
  National Weather Centres computer, where it
  becomes part of the inputs the computer needs to
  track and predict the national weather picture)

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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)

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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)

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Printers

• The main types of printers are
• Ink-jet printers
• Laser printers
• Dot matrix printers
• Thermal printers
• Multifunctional printer

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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

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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

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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

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Ink-jet printers
Print head
Stepper motor
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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

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Ink-jet printers
Stabiliser bar and belt
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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

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Ink-jet printers
Rollers
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Ink-jet printers - Advantages

• Ink-jet printers
• Can produce high quality printouts (including
  photographs)
• Are quiet when operating
• Are cheap to buy

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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

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Laser printers

• Laser printers are popular with business users
• They work by using photocopier technology and
  toner to produce printed outputs

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Laser printers
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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
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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
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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
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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
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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"
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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)
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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
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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
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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
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Laser printers
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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

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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

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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

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Dot matrix printers
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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

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Dot matrix printers
Dot matrix printer head
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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.

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Dot matrix printers - Advantages
Continuous feed paper
NCR (no carbon required) forms
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Dot matrix printers - Advantages

• Their reliability because they use simple
  technology that rarely fails
• Their ability to switch between different paper
  sources

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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

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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

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Thermal printers
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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

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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

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Multifunctional printers
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AS Level ICT

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