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Output Devices

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Output Devices

Output devices are peripherals that can display data or information to the user.

You should be able to do the following

CRT Monitor

These monitors are easy to identify as they have large bulky backs behind a glass screen. They used to be the most common monitors for use with desktop computers. These days other Monitor types have become cheaper and so CRT monitors are not commonly seen except in old equipment.

Advantages and disadvantages

  • Cheap to buy
  • Produces good colours
  • Large footprint so takes up lots of desktop space.
  • Very heavy compared to other monitor types
  • Screen is generally convex and this makes output at the edges slightly distorted.

CRT stands for 'Cathode Ray Tube' and refers to the operation of the display. Electrons ( also called cathode rays) are fired at the screen which is coated in small dots. Each dot contains red, green and blue phosphorpous. The electrons hit the phosphorous dots and these glow to produce the correct colour. The electron gun is positioned behind the glass screen which is why the back protrudes so much. The entrire screen and gun assembly have to be under vacuum. This requires thick glass to prevent implosion. That is why these screens are so heavy.

TFT Monitor

These are the most common type of computer monitor at present. They use LCD technology which requires backlighting to enable the image to be seen.

Advantages and disadvantages

  • Thinner and lighter then CRT monitors making them suitable for portable products
  • The back lighting does not evenly light the screen causing dark and light patches
  • Narrow viewing angle - Picture quality changes as the viewer moves around.

Multimedia Projector

Computer screens are too small to show something to an audience. Multimedia projectors plug into computers and the normal image on the display is projected onto a large screen.

Advantages and disadvantages

  • Allows larger numbers of people to see what is on the computer display
  • Bulp lifetime is limited and bulbs are expensive to replace
  • Often require significant distance between screen and projector so require large rooms to work

Laser Printer

Laser printers are the main types of printers found in offices and businesses. They produce high quality printouts of both text and graphics and cn produce both colour and gray scale output.

Advantages and disadvantages

  • More expensive to buy a laser printer than an inkjet printer
  • Less expensive to print per page than an inkjet printer.
  • Produce very high quality output

Inkjet Printer

Inkjet printers produce a printout by emitting small drops of ink onto paper. They are not impact printers. Inkjet printers are very common for home printing requirements.

Advantages and disadvantages

  • Produce high quality printouts in colour
  • Cheap to purchase the printer initially
  • Quieter than impact printers such as dot-matrix
  • High ink costs per page
  • Printouts may not be touch-dry when first produced so will smudge if not handled carefully

Dot Matrix Printer

Dot-matrix printers are impact printers. They work by striking the page with small pins coated in ink at the tip. They used to popular in home printing applications but have now been mostly replaced by inkjet printers. There main use is in printing multi-part forms which require the impact to imprint the character through to the last page.

Advantages and disadvantages

  • Very fast for printing text
  • Can print onto multi-part forms because they use impact to work (the other types of printer mentioned are non-impact).
  • Very noisy so not suitable for offices due to noise polution.
  • Still popular in wharehouses, or similar, where noise is less of an issue and mutli-part form use is still common.
  • Produce very poor image quality only really suitable for text

Graph Plotter

Also called a 'plotter' these are used to printout line drawings in situations like architects or engineering diagrams. There are two types

  • Flat-bed plotters - The paper lies on flat surface and pens are moved across the surface to draw diagrams
  • Drum-plotters - The paper is on a roll and as it unrolls pens draw on it.

Advantages and disadvantages

  • Can work on very large paper sizes
  • Produce very high quality line drawings
  • Very large and so take up lots of office space
  • Very expensive top buy the plotter
  • Pen plotters have mostly been replaced by very large injet printers in most situtions

Speakers

Enable a computer to output sounds as long as there is a sound card fitted into the computer.

Advantages and disadvantages

  • Enable to uers to hear sounds - useful for feedback for visually impaired people
  • Enables computers to be used a multimedia devices such as in video playback with sound
  • Require desktop space

Motors

Allows a computer to make other equipment move such as microwaves, washing machines and robots.

Advantages and disadvantages

  • Enables computers to control automated equipment.
  • Requires additional equipment like D2A converters to enable computers to control motors

Buzzer

Buzzers enable feedback to users such as alarms for microwaves once they have finished.

Advantages and disadvantages

  • Enables computers to give audible feedback if the user is not able to see the device.
  • Noise can be intrusive in situations where low noise levels are important

Lights

Found in computer controlled greenhouses, steeet lighting and traffic lights.

Advantages and disadvantages

  • Improve the productivity of the greenhouse by maximising the amount of light for the plants.
  • Makes driving safer by autmatically turning on when it is dark

Heaters

Used in computer controlled greenhouses. In colder climates and at night the computer can turn the heater on to maintain the optimum temperature for the plants growth.

Advantages and disadvantages

  • Improve the productivity of the greenhouse by maximising the temperature for the plants.
  • Enables the growth of plants which would not grow in colder climates
  • Excessive use of heaters and lights to grow non-native plants contributes to atmospheric warming