Output Devices

Output Devices Overview
- Output devices are crucial components of a computer system as they deliver the results of processed data to the user.
- Nishat Tasnim Sithy, Lecturer, Dept of CSE, Eastern University.

General
- Most common output device connected to the video card.
- Categorized by color output:
  - Monochrome: One color with black background.
  - Grayscale: Varying degrees of gray.
  - Color: Displays between 4 to 16 million colors.
Cathode Ray Tube (CRT)
- Most common type of monitor.
- Utilizes electrons fired from the back to excite phosphors causing them to glow.
- The surface is arranged in dots called pixels with a dot mask ensuring appropriate pixel illumination.

Conversion of Signals
- Converts electrical signals (voltage, current) into visual signals.
- Electron gun emits electrons that are focused into a beam directed at the picture tube.
Phosphor Coating
- The tube is coated with small phosphor dots that glow according to the strength and duration of the beam.
- The focusing system ensures the electron beam focuses correctly on the screen.
- Horizontal and vertical deflectors allow targeting various screen spots.
Color Systems
- Employs groups of three different phosphors (red, green, blue) for color representation.

Types of Light Emission
- Fluorescence: Light emitted during the excitation by electrons.
- Phosphorescence: Light emitted after the electron beam is removed.
- Persistence: Duration until phosphorescence decays to 10% of original light intensity.
  - High persistence phosphors: lower refresh rates, minimize flicker.
  - Low persistence phosphors: require high refresh rates to prevent flicker.
CRT Color Representation
- Phosphor dots arranged in triads (red, green, blue) blend to create various colors.
- Varying intensity adjusts colors seen on the screen.

Overview
- Commonly found on laptops, also available in desktop versions.
- Address issues present in CRTs; fluorescent lights provide illumination.
Matrix Types
- Passive Matrix LCD
  - Controlled by row & column electrodes; slower display response.
- Active Matrix LCD
  - Each pixel has its own Thin Film Transistor (TFT), allowing for faster response and better clarity.

Drawbacks
- Higher cost compared to CRTs.
- Best viewing from directly in front; poor viewing angles.
- More fragile than CRTs, potentially leading to damage.

Innovative Displays
- Paper-white displays: High contrast.
- Electro-luminescent displays: Similar to LCD but uses phosphors.
- Plasma monitors: Utilize excited gas to produce light.

Importance
- Affects user productivity with attributes like crisp text and clear graphics.
- Monitors should have adjustable controls and clear edges.

Key Features
- Size: Measured diagonally.
- Resolution: More pixels equate to sharper images.
- Refresh Rate: Higher rates reduce eyestrain.
- Dot Pitch: Smaller values yield finer images; ideal dot pitch should be less than 0.22 mm.

Functionality
- Positioned between CPU and monitor, improving output capability.
- Lessens CPU workload on drawing graphics; modern cards often contain up to 512 MB of RAM and handle 3D rendering.

Eyestrain Prevention
- Steps to avoid eyestrain include proper monitor distance and positioning, minimizing glare.
- EMF Exposure
- Electromagnetic fields generated by electronic devices can pose health risks; maintaining distance and using LCD monitors are recommended.

Functionality
- Replaces older projection methods (overhead/slides).
- Uses mirrors and LCD technology to display images, generally in dark environments for optimal clarity.

Functions
- Essential for recording/playback functionality.
- Sound Card
- Connects CPU to speakers, converting digital sounds to analog. Modern sound cards support advanced audio like Dolby Surround Sound.
Headphones and Headsets
- Provide private audio for users, minimizing external noise disruptions.