Output devices

Prof. K Regis

Types of output devices

• Monitor

• Printer

• Speaker

• Plotter

Monitors

• It’s the most important output device• 2 common types

– CRT– LCD

• Featured by:– Refresh rate– Resolution– Visible screen size– Response time

CRT monitors

• This acronym stands for Cathode Ray Tube

• Very widespread• Cheap• Good performance

Working method of CRT monitor

• The back of the tube has a negatively charged cathode, so called electron gun. The electron gun shoots electrons down the tube and onto a positively charged screen. The screen is coated with a pattern of red, green and blue phosphor dots that will glow when struck by the electron stream. The three dots together make up a pixel.

LCD screens

• LCD means Liquid Crystal display

• Good quality• Environment friendly

(no lead in the glass)

How it works?

• There is a thin liquid cristal layer between a horizontal and a vertical filter. Thanks to an appropriate voltage liquid cristals get arranged and light can pass the filters. This light will appear on the screen.

• In color LCDs each individual pixel is divided into three cells, or subpixels, which are colored red, green, and blue. Each subpixel can be controlled independently to yield thousands or millions of possible colors for each pixel.

Printers

• A computer printer, or more commonly just a printer, is a device that produces a hard copy of documents stored in electronic form, usually on physical print media such as paper.

• In addition, many modern printers can directly interface to electronic media such as memory sticks or memory cards, or to image capture devices such as digital cameras, scanners; some printers are combined with a scanners and/or fax machines in a single unit.

Main types of printers

• Dot matrix

• Inkjet

• Laser

• Thermal

Dot matrix printer

• A dot matrix printer or impact matrix printer refers to a type of computer printer with a print head that runs back and forth on the page and prints by impact, striking an ink-soaked cloth ribbon against the paper, much like a typewriter. Unlike a typewriter, graphics can be produced.

Inkjet printers

• Inkjet printers are a type of computer printer that operates by propelling tiny droplets of liquid ink onto paper. They are the most common type of computer printer for the general consumer due to their low cost, high quality of output, capability of printing in vivid color, and ease of use.

Laser PrintersLaser printers are printer that uses laser technology to print images on the paper. These work in a manner similar to a photocopier. The laser recreates the image on a negatively drum. A roller is charged with electricity, then a laser is used to remove the charge from portions of the roller. Powdered ink (toner) sticks to the parts of the roller that were hit by the laser, and this toner is transferred from the roller to the paper. Then the ink is baked into the paper using a heater.

Speaker

• Speakers allows the computer to display sound.

• There are built-in ones, but you can choose external types too. It’s better, because it provides a better quality even can perform surround sounding which is the best choice for games and videos.

Plotter

• A plotter is a vector graphics printing device that connects to a computer.

• Plotters print their output by moving a pen across the surface of a piece of paper. This means that plotters are restricted to line art, including text, but do so very slowly because of the mechanical movement of the pens. Plotters are used primarily in technical drawing where they have the advantage of working on very large paper sizes while maintaining high resolution.

Happy end