Patrick Janvarius's blog Basic-knowledge-computer

Output devices


Introduction to output devices

An output device is any piece of computer hardware equipment which converts information into human readable form . It can be text , graphic ,tactile , audio or video information into a human readable form . 
 
Examples includes monitors , printers, speakers, headphones , projectors, GPS devices , Optical Mark 
readers, and braille readers.


Following are some of the important output devices used in a computer.

  • Monitors
  • printers
  • speakers 
  • Headphone 
  • Graphic Plotter
  • Printer
  •   GPS devices
  •   Optical Mark reader 
  •  Braille readers 

Monitors


Monitors, commonly called as Visual Display Unit (VDU), are the main output device of a computer. It forms images from tiny dots, called pixels that are arranged in a rectangular form. The sharpness of the image depends upon the number of pixels.

There are two kinds of viewing screen used for monitors.



  • Cathode-Ray Tube (CRT)
  • Flat-Panel Display
  • Cathode-Ray Tube (CRT) Monitor

    The CRT display is made up of small picture elements called pixels. The smaller the pixels, the better the image clarity or resolution. It takes more than one illuminated pixel to form a whole character, such as the letter ‘e’ in the word help.

    CRT Monitor

    A finite number of characters can be displayed on a screen at once. The screen can be divided into a series of character boxes - fixed location on the screen where a standard character can be placed. Most screens are capable of displaying 80 characters of data horizontally and 25 lines vertically.

    There are some disadvantages of CRT −




    • Large in Size
    • High power consumption

Flat-Panel Display Monitor

The flat-panel display refers to a class of video devices that have reduced volume, weight and power requirement in comparison to the CRT. You can hang them on walls or wear them on your wrists. Current uses of flat-panel displays include calculators, video games, monitors, laptop computer, and graphics display.

Flat Monitor

The flat-panel display is divided into two categories −

  • Emissive Displays − Emissive displays are devices that convert electrical energy into light. For example, plasma panel and LED (Light-Emitting Diodes).

  • Non-Emissive Displays − Non-emissive displays use optical effects to convert sunlight or light from some other source into graphics patterns. For example, LCD (Liquid-Crystal Display).


Printers

Printer is an output device, which is used to print information on paper.

There are two types of printers −

  • Impact Printers
  • Non-Impact Printers

Impact Printers

Impact printers print the characters by striking them on the ribbon, which is then pressed on the paper.

Characteristics of Impact Printers are the following −

  • Very low consumable costs
  • Very noisy
  • Useful for bulk printing due to low cost
  • There is physical contact with the paper to produce an image

These printers are of two types −

  • Character printers
  • Line printers

Character Printers

Character printers are the printers which print one character at a time.

These are further divided into two types:

  • Dot Matrix Printer(DMP)
  • Daisy Wheel

Dot Matrix Printer

In the market, one of the most popular printers is Dot Matrix Printer. These printers are popular because of their ease of printing and economical price. Each character printed is in the form of pattern of dots and head consists of a Matrix of Pins of size (5*7, 7*9, 9*7 or 9*9) which come out to form a character which is why it is called Dot Matrix Printer.

Dot Matrix Printer

Advantages

  • Inexpensive
  • Widely Used
  • Other language characters can be printed

Disadvantages

  • Slow Speed
  • Poor Quality

Daisy Wheel

Head is lying on a wheel and pins corresponding to characters are like petals of Daisy (flower) which is why it is called Daisy Wheel Printer. These printers are generally used for word-processing in offices that require a few letters to be sent here and there with very nice quality.

Daisy Wheel Printer

Advantages

  • More reliable than DMP
  • Better quality
  • Fonts of character can be easily changed

Disadvantages

  • Slower than DMP
  • Noisy
  • More expensive than DMP

Line Printers

Line printers are the printers which print one line at a time.

Line Printer









  •    These are of two types −
    • Drum Printer
    • Chain Printer

    Drum Printer

    This printer is like a drum in shape hence it is called drum printer. The surface of the drum is divided into a number of tracks. Total tracks are equal to the size of the paper, i.e. for a paper width of 132 characters, drum will have 132 tracks. A character set is embossed on the track. Different character sets available in the market are 48 character set, 64 and 96 characters set. One rotation of drum prints one line. Drum printers are fast in speed and can print 300 to 2000 lines per minute.

    Advantages

    • Very high speed

    Disadvantages

    • Very expensive
    • Characters fonts cannot be changed

    Chain Printer

    In this printer, a chain of character sets is used, hence it is called Chain Printer. A standard character set may have 48, 64, or 96 characters.

    Advantages

    • Character fonts can easily be changed.
    • Different languages can be used with the same printer.

    Disadvantages

    • Noisy

    Non-impact Printers

    Non-impact printers print the characters without using the ribbon. These printers print a complete page at a time, thus they are also called as Page Printers.

    These printers are of two types −

    • Laser Printers
    • Inkjet Printers

    Characteristics of Non-impact Printers

    • Faster than impact printers
    • They are not noisy
    • High quality
    • Supports many fonts and different character size

    Laser Printers

    These are non-impact page printers. They use laser lights to produce the dots needed to form the characters to be printed on a page.

    Laser Printer

    Advantages

    • Very high speed
    • Very high quality output
    • Good graphics quality
    • Supports many fonts and different character size

    Disadvantages

    • Expensive
    • Cannot be used to produce multiple copies of a document in a single printing

    Inkjet Printers

    Inkjet printers are non-impact character printers based on a relatively new technology. They print characters by spraying small drops of ink onto paper. Inkjet printers produce high quality output with presentable features.

    Inkjet Printer

    They make less noise because no hammering is done .

    Advantages

    • High quality printing
    • More reliable

    Disadvantages 


    • Expensive as the cost per page is high
    • Slow as compared to laser printer any styles of printing modes available. Color printing is also possible. Some models of Inkjet printers can produce multiple copies of printing also.


  • Braille reader

    a Braille reader  also called a braille display , is an electronic device that allows a blind person to read the text display on a computer monitor. 
    The Computer sends the text from specialized software to the output device,  where it is converted to braille and displayed by raising rounded pins through a flat surface. 
    Braille reader comes in various form including large scale . ( about size of computer board ) and smaller board is designed to work with laptop and tablet computers . There are also braille reader app for smart phone  and tablets that work in conjunction with braille blue tooth out put device. 
    the picture below is orbit reader 20. 
    An example of braille reader . 






Speaker 


1.speaker may refer to any of the following.
Speaker is term used to describe the user who is giving vocal commands to software program.
2 . A computer speaker is an output hardware device that connect to computer to generate sound. 
The signal is used to produce the sound  that comes from the computer speaker is created by computer's sound card.


How do speakers work?

Speakers are made up of a cone, an iron coil , magnet, and housing ( case) . When the speaker receives electrical input from device, it sends the current through the causing it to move back and forth . This motion then vibrates the outer cone generating sound waves picked up by our ears. 


Evolution of speaker





when computer were initially released . 
They had on board speaker built into chassis that generated different tone  and beeps . . 

The first internal speaker were invented by I BM  in 1981 produced basic low quality sound. 

As technology progressed on board speaker moved into the computer monitor and acquired ability to produce  the sound , music, sound effects . 
monitor speaker were on left-bottom and right -bottom front of the computer. 
However, some computer had speakers built into right and left side to the computer. 

When computer gaming, digit music, and  other media becomes popular.  

Manufacturers  began  to make external speaker that produced high quality sound and improved bass.