Transcript Data Protection

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