Output devices

Introduction

In this presentation we will talk about Output device.

Output device are very useful. For example monitor, printer and

speakers.

Monitors

Picture on monitor are made out of thousands of colour dots called pixels.

Higher the pixel higher the quality.

There are two type of monitor› Cathode ray tube (CRT)› Thin film Transistor (TFT)

Cathode ray tube

CRT are outdated Large and bulky Glass screen Produce a lot of heat Noisy compare to TFT

Thin film transistor

Replacement of OCR Nicer and take up less

space They are quieter than

CRT Easily to damage The colour and contrast

are not so good as a CRT. Unless you have a very high quality one.

The picture can look a bit dull.

Printers

They are use to create a hard copy of your work.

Most printer produce work on paper.

There are 4 type of printer› Laser printers› Ink-jet printers› Dot-matrix printers› Plotters

Laser printer

Quiet Print large number of sheets

very quickly and they produce high quality documents.

Used powdered ink called toner Cost per page is low Most expensive printer to buy Toner are more expensive than

ink-jet cartidges. Larger than ink-jet Can’t create carbon copies like

the dot-matrix.

Ink jet Printers

Cheap to buy Can combine both black and white

and colour printing at the same time

Use cartridges which contain ink Useful for few document needed

and the quality of the printout doesn’t need to be perfect.

They are more compact than laser Cartridges cost less to replace than

toners. Better quality than dot-matrix Slower than laser Noiser than laser Cartridges need to be replace more

often than laser Cartridges can dry out

Dot-matrix

Impact printer Different combination of pins

are pushed out to form different characters.

Very noisy It is useful when you need

carbon copies like bills. Cheap to buy Low operating cost Can print continuously Create carbon copies Poor quality Very slow to print Noisy Cannot produce colour copies.

Plotters

Specialist type of printer which able to draw high quality image over a very large piece of paper.

Used by engineers, architects and map-makers.

A plotters uses pen to draw images. There are now pen-less plotters. Drawing are the same quality as the

expert. Larger sizes of paper can be used than

most printers Slower than other printer More expensive than printer Do not produce high quality text

printout. There are 3 different type of plotters

› Flatbed-hold the paper still while the pen move

› Drum plotters- these roll paper over the cylinder

› Pinch-rollers plotters- these are a mixture of the two type above.

Speakers

Most computer fit a small internal speakers which will produce a beeping sound when you made an error.

Everyone in the room can hear output from computer.

Help to create atmosphere Help blind people to use

computer The sound can disturb other

people while they are trying to do their work.

High quality speakers can be expensive

Lights (LEDs)

Light can be connect to computer and respond to the signal which tell them to switch on or off

Used in a computer to help to show that it is working correctly

Can provide warnings They come in large range of

different colours The bulbs can break or wear

away If there are loose

connections the bulb might not work.