Chapter 2B
Output Devices
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2
Learning Objectives
2.5
2.6
2.7
2.8
Describe the most common types of computer
monitors
Identify the reasons sound systems are useful
Compare the most widely used types of printers
Describe other devices that a computer can use
for output
© 2013 by the McGraw-Hill Companies, Inc. All rights reserved.
3
Monitors
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4
Types of Monitors
• Cathode ray tube (CRT) monitors are powered by a
large vacuum tube
• Flat-panel displays are a thinner alternative to a CRT
– Most flat-panel monitors have a liquid crystal display
(LCD)
– LED monitors use tiny electronic lights called lightemitting diodes (LEDs)
• Specialized monitors include:
– Paper-white displays
– Electroluminescent displays (ELDs)
– Plasma displays
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5
Comparing Monitors
• Some factors worth considering:
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–
–
–
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Size
Text display
Image display
Resolution - the number of pixels displayed on the screen
Response rate - amount of time in a milliseconds that it
takes for a pixel to change from black to white
– Contrast ratio - how close the monitor can get to perfect
black and white
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Comparing Monitors, cont’d.
• Other factors worth considering include:
– Viewing angle - measures how far to the side a user can
be before the picture fades or blurs
– Refresh rate - the number of
times per second that the
monitor draws its visible image
– Dot pitch - the distance between
the like-colored phosphor dots
of adjacent pixels
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7
Video Card
• A video card contains the video-dedicated memory
and sends information to the monitor for display
• The quality of images displayed depends as much on
the video card as on the monitor
• Video cards now commonly support at least two
displays
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8
Ergonomics and Monitors
• Eyestrain is fatigue of the eyes caused by focusing on
the same point for too long
– One of the most frequently reported health problems
associated with computer use
• Measures to reduce eyestrain:
– Choose a monitor that does not
flicker
– Position your monitor 2 to 2-1/2
feet away from your eyes
– Avoid looking at the monitor for
more than 30 minutes
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9
Sound Systems
• Sound system devices include:
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–
–
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Microphones
Speakers
Headphones and headsets
Sound cards - circuit boards
that convert sound from analog
to digital form, and vice versa
– Sound editing programs
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10
Printers
• Basic categories:
– Impact printers - create an image by striking an inked
ribbon against paper
– Nonimpact printers - use other means to create an image
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11
Types of Printers
• Dot matrix printers are impact printers where
physical impact with the paper is important
– The printer creates an image by using mechanism called a
print head
• Inkjet printers create an image by spraying ink
• Laser printers rely on a laser to print
• All-in-one printers combine a printer with scanning,
photocopying, and faxing capabilities
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12
Special-Purpose Printers
• Dye-sublimation (dye-sub) printers produce realistic
quality and color for photo images
• Photo printers use inkjet or dye-sub technology to
create high-quality images
• Thermal-wax printers operate with a ribbon coated
with panels of colored wax that melts and adheres to
the paper
• Plotters are used to print large-format images
• Line printers uses a wide print head
• Band printers uses a rotating band embossed with
alphanumeric characters
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Comparing Printers
• The selection of a printer should be based on the
kinds of output needed, as well as the following
considerations:
– Cost
– Image quality: The more dots per inch (dpi) a printer can
produce, the higher its image quality
– Speed: Printer speed is measured in pages per minute
(ppm)
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14
Projectors
• Digital light processing (DLP) projectors have
millions of microscopic mirrors that shift to reflect
the source of light
• Methods of accepting output
– Hooked up to the computer
as a monitor
– Via a local network of
computers
– From a USB flash drive
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15
SMART Boards
• SMART boards - digital versions of the whiteboards
– The board attached to the
wall is a touch-sensitive
input device
– Short-throw projector designed to be used very
close to the display area
– Special pens and an eraser
are used for input
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16
Haptic Feedback
• Haptic feedback - the communication of vibration,
motion, or physical resistance
– Game controllers often include mechanical motion
generators
– Haptic feedback increases the user’s sense of immersion in
the game
– Force feedback is the application of motion to a controller
together with a visual event
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17
Computer-aided Manufacturing
• Computer output is used to drive industrial
machinery and robot production in many different
manufacturing industries
• Computer instructions coordinate and control
several different motors in a robotic arm
• Applications include:
– Welding cars
– Drilling holes precisely
– Fabricating tiny computer chips
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