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Lecture 09-10

Computer Applications to Business

Video and Sound

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Monitors• Most common output device

• Connects to the video card (also called the video adapter or graphics adapter) .

• In General, two types of monitors are used with PCs:1. Cathode Ray Tube(CRT)2. Flat-Panel Display

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• Monitors can be categorized by color output:– Monochrome monitors• One color (such as green , amber or white) with black

background.• Used for text-only displays.

– Grayscale monitors• Varying degrees of gray.• Used in low-end portable systems. Eg; Handheld

computers.– Color monitors• Display 4 to 16 million colors

Monitors

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Monitors

• Cathode Ray Tube (CRT)– Most common type of monitor

– Electrons fired from the back

– Electrons excite phosphor to glow

– Phosphor is arranged in dots called pixels

– Dot mask ensures proper pixel is lit

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CRT Monitor

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CRT Monitor

1. Electron guns2. Electron beams3. Focusing coils4. Deflection coils5. Anode connection6. Mask for separating beams for red, green, and blue part of displayed image7. Phosphor layer with red, green, and blue zones8. Close-up of the phosphor-coated inner side of the screen

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CRT Monitor

• CRT color– Phosphor dots arranged in triads

– Red, green, and blue dots

– Three colors blend to make colors

– Varying the intensity creates new colors

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CRT Monitor

• CRT drawbacks– Very large

– Very heavy

– Use a lot of electricity

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Flat-Panel Monitors

• Flat panel displays encompass a growing number of technologies enabling video displays that are lighter and much thinner than traditional television and video displays that use cathode ray tubes, and are usually less than 4 inches (100 mm) thick.

• The Flat panel displays require continuous refresh.

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These flat panel displays has given the birth to the number of technologies which include:

» Digital Light Processing (DLP)

» Plasma Display Panels (PDPs)

» Liquid Crystal Displays (LCDs)

» Organic Light-Emitting Diode Displays (OLEDs)

» Light-Emitting Diode Display (LED)

Flat-Panel Monitors

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Monitors

• Liquid Crystal Display (LCD)

– Commonly found on laptops

– Desktop versions exist

– Solve the problems of CRT

– Fluorescent lights provide illumination

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Monitors

• There are two types of LCDs:

1. Passive matrix LCD

2. Active matrix LCD

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1) Passive matrix LCD– Pixels arranged in a grid– Pixels are activated indirectly• Row and column are activated

– Animation can be blurry– Refresh rate is slower– Submarining.• If you move the pointer too quickly, it seems to

disappear.

Monitors

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Monitors

2) Active matrix LCD– Each pixel is activated directly– Pixels have 4 transistors(TFT Technology)• One each for red, green, blue• One for opaqueness

– Transistors arranged in a thin film– Animation is crisp and clean

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Monitors

• Drawbacks to LCD– More expensive than CRT

– Must sit directly in front of screen

– Can be more fragile than CRT

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Other types of Monitors

• Paper-white displays– High contrast between fore and background– Used by document designers

• Electro-luminescent displays (ELD)– Similar to LCD– Uses phosphor to produce light

• Plasma monitor– Gas(neon or xenon) is excited to produce light between

two sheets of glass.

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Monitors

• Monitors impacts user effectiveness• Monitors should have:– Crisp text

– Clear graphics

– Adjustable controls

– Clear edges

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Comparing Monitors

• Size of monitor• Resolution• Refresh rate• Dot pitch

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Monitors and Video Cards

• Size of monitor– Measured in inches– Measured diagonally– Actual size• Distance from corner to corner

– Viewable size• Useable portion of the screen

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Monitors and Video Cards

• Resolution– The term resolution refers to the sharpness or clarity of an

image.

– A monitor’s resolution is determined by the number of pixels on the screen, expressed as a matrix.

– Higher number creates sharper images

– Higher number creates smaller images

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Monitors and Video Cards

– Refresh rate – A monitor's refresh rate is the number of times per second

that the electron guns scan every pixel on the screen.

– When purchasing a monitor; look for one with a refresh rate of 72 Hz or higher.

– Modern equipment sets this automatically

– Improper settings can cause eyestrain

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Monitors and Video Cards

• Dot pitch– Distance between the same color dots

– If you measure the distance between the red dots of two adjacent pixels, you are measuring the monitor's dot pitch.

– Ranges between .15 mm and .40 mm

– Smaller creates a finer picture

– Should be less than .22

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Video Cards

• Device between the CPU and monitor

• The quality of the images that a monitor can display is defined as much by the video card as by the monitor itself.

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Video Cards

• Better cards result in better output

• Removes burden of drawing from CPU

• Have their own processor and RAM

• Modern cards have up to 512 MB RAM

• Capable of rendering 3D images

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Ergonomics and Monitors

• Eyestrain– Fatigue of the eyes• caused by focusing on the same point for too long.

– Steps to avoid• Choose a good monitor• The dot pitch should be no greater than 28 mm.• Refresh rate should be at least 72 Hz.• Place the monitor 2 – 3 feet away• Center of screen below eye level• Avoid reflected light

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Ergonomics and Monitors

• Electronic magnetic fields (EMF)– Generated by all electronic devices– EMF may be detrimental to health– Steps to avoid• Keep the computer at arms length• Take frequent breaks• Use an LCD monitor

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Data Projectors

• Replaced overhead and slide projectors• Data projectors are also called digital light projectors and

video projectors.• Project image onto wall or screen

• LCD projectors – Are most common type of projector– Small LCD screen– Very bright light– Require a darkened room

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Data Projectors

• Digital Light Projectors– A series of mirrors control the display– May be used in a lighted room

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Sound Systems

• Integral part of the computer experience

• Capable of recording and playback

• Microphones arc now important input devices, and speakers and their associated technologies are key output systems of the sound system.

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Sound Systems

• Sound card– Device between the CPU and speakers

– Converts digital sounds to analog and vice versa.

– Can be connected to several devices

– A sound card actually has both input and output functions.

– Modern cards support Dolby Surround Sound

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Sound Systems

• Headphones and headsets– Replacement for speakers and microphones– Offer privacy– Does not annoy other people– Outside noise is not a factor– Headsets have speakers and a microphone