Video and multimedia inputoutput devices

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Video and multimedia input/output devices

• Unit objectives
• Describe, install, and troubleshoot CRT displays
• Describe, install, and troubleshoot LCD displays
• Connect and use speakers and a microphone
• Connect and troubleshoot scanners and digital
  cameras

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CRT (Cathode Ray Terminals) monitor
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CRT components

• Cathode- A heated element at the rear of the
  monitor. When heated negatively charged rays are
  emitted. These are attracted by positively
  charged anode..
• Anode -The anode focuses the rays
• Phosphors- RGB light phosphors are arranged in a
  triad of dots or in strips. The three electron
  beams allow the dots to be illuminated
  simultaneously. The high speed electron beam
  passes through a device that positions the
  electronic beams and strikes the phosphor coated
  screen.
• Pixel triad Is the grouping of the three color
  dots.
• Electronic beam positioning
• Shadow mask is a sheet of metal with a hole for
  each pixel triad.
• Aperture grill Is composed of thin vertical
  metal strips to block stray electrons.
• Slotted mask Combines features of shadow mask
  and aperture grill

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How CRTs produce images
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More CRT demonstration
Abbreviation of cathode-ray tube, the technology
used in most televisions and computer display
screens. A CRT works by moving an electron beam
back and forth across the back of the screen.
Each time the beam makes a pass across the
screen, it lights up phosphor dots on the inside
of the glass tube, thereby illuminating the
active portions of the screen. By drawing many
such lines from the top to the bottom of the
screen, it creates an entire screenful of images.
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CRT characteristics

• Screen size is the diagonal measurement , in
  inches of the entire picture tube.
• Aspect ratio is the relationship btn the
  horizontal size and the vertical size of the
  screen. A standard monitor has 43 ratio. The
  same size as a standard TV set.
• Resolution refers to the number of pixels on
  the display device. The resolution is expressed
  in rows and columns. A monitor with 1280 x 1024
  resolution has 1280 rows of dots and 1024
  columns of dots.
• Refresh rate The number of times per second the
  screen is redrawn, This is measure in Hertz (Hz).
  At 60 Hz the monitor is refreshed 60 times in one
  second. The image appears more stable with less
  flickering at higher refresh rates. The human eye
  does not notice the redraw at 72Hz or higher.
• Dot pitch The distance measured in millimeters ,
  between the same color dots on the screen. Most
  monitors have a dot pitch btn 0.15 and 0.30 mm.
  The smaller the dot pitch number the better the
  image. An average quality monitor has between
  0.22 and 0.26 dot pitch.
• Flat or curved screen Traditionally TV and
  monitors contained a curved screen. The edges of
  the display were slightly distorted. Newer
  monitors are almost all flat screens. Flat
  screens are clear across the entire surface.
  Flat screen is different from a flat panel
  monitor, Flat screen CRTs still use the cathode
  ray tube, and the dimensions of the monitor are
  quite deep usually as deep as they are high.

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Video connectors
15 pin D connector Each pin carries certain
Information.
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Display properties

• Screen resolution-- In computers, resolution is
  the number of pixels (individual points of color)
  contained on a display monitor, expressed in
  terms of the number of pixels on the horizontal
  axis and the number on the vertical axis. The
  sharpness of the image on a display depends on
  the resolution and the size of the monitor. The
  same pixel resolution will be sharper on a
  smaller monitor and gradually lose sharpness on
  larger monitors because the same number of pixels
  are being spread out over a larger number of
  inches.
• Color quality
• Monitor settings
• Color depth Describes how many bits are used to
  describe the color of a single pixel.

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Display adjustments

• Brightness
• Contrast
• Position of image on screen
• Adjustment method varies by monitor

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CRT issues

• Screen is black
• Image flickers or distorts
• Noisy monitor
• Image scrolling
• Video Display Troubleshooter

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Flat panel monitor
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LCD (Liquid Crystal Display) advantages

• Less power is used
• Less heat is created
• Use less desk space
• Less glare
• Less radiation emitted

Uses thin-film transistor (TFT) Technology
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How a flat panel screen works