Output Devices

OUTPUT DEVICES

Output devices enable us to perceive the results of computer processing- to see these results, to hear them, and even to feel them. There are many types of output devices like monitor, speaker, plotters, printers, etc.

1. MONITORS

Monitors also called as displays or VDU displays the video adapter’s output. The on-screen display enables us to see how applications are processing our data, but it’s important to remember that the screen display isn’t permanent record. To drive home this point, screen output is sometimes called softcopy since we can only feel it and not touch it. There are two types of monitors in the market. They are:

a) CRT Monitors

CRT Monitor

CRT(Cathod Ray Tubes) monitors are like our commonly used television set in our home which consists of electron gun which fires electrons rapidly which passes through magnetic coil and strikes the phosphorus coated screen and the coated starts to glow forming image on it. There are again two types of CRT Monitors. They are:

Color CRT Monitor

i. Monochrome CRT Monitors

They have only one electron gun present for producing black and white colors.

ii. Color CRT Monitors

They have three electron guns present for producing RGB (Red, Green and Blue respectively) Colors.

b) Flat Panel Monitors

Flat Panel Monitors

A flat Panel monitor is smaller in size. They are highly portable and consumes less power but images produced in flat panel are less bright the CRT monitors which makes it safe for our health point of view. They are also more expensive than CRT monitors. They are classified on the basis of the substance used. On the basis of substance used, they are classified into three types of monitors which are:

i. LCD Monitors (Liquid Crystal Display)

LCD Monitor

In LCD monitors, liquid substance is used in between the two plates. This liquid becomes opaque when charged with the electricity and image is formed.

ii. ELD Monitors( Electrolumincient Display )

In ELD monitors, solid substance is used in between the plates. This solid substance starts to glow when charge with the electricity and image is formed in the screen.

iii. Gas Plasma

In Gas Plasma monitor, gas substance is used in between the plates. This gas substance starts to glow when charge with the electricity and image is formed in the screen.

2. PLOTTERS

Plotters is specialized hard copy output device which can produce high quality graphics. Specially, plotters are designed for producing high quality map and architectural drawing.

On the basic of working principle, plotters can be divided into three types.

 They are:

Pen Plotter

a. Pen Plotters

Pen Plotters may consist 1 to 4 pens having different color(s). At the bottom the pen(s) a flat of paper is moved to plot on the paper. This plotter can produce up to 4 colors.

b. Electrostatic Plotters

Electrostatic plotters use electrostatic charges to produce tiny dots on a specialized paper. When a paper is run through the developer, a image is produced on the paper. It is also capable of producing 4 colors.

Thermal Plotter

c. Thermal Plotters

Thermal Plotters consists of heated heads and a special type of heat sensitive paper when the heated heads are moved on the paper, image can be plotted on the paper. This plotter is capable of producing 2 colors.

3. VOICE RECOGNITION UNIT

Computer equipped with sound card can accept sound input from a microphone. The sound card translates digital sounds into the electric current that is sent to the speakers. Sound cards are essential for multimedia computers with CD-ROMS which has become common on all personal computers.

Sound Card

In PCs, a sound card is an expansion board designed to record and play back sound files. Sound files contain digitized sound data, which is saved to one of several standardized sound formats. These formats specify how sounds should be digitally represented, and generally include some type of data compression that reduces the size of the file. Examples of popular sound file formats are the Windows WAV format, AU sound (a low quality, monaural sound format often encountered on the Internet), and Motion Pictures Expert Group (MPEG) audio formats (called MP-2 and MP-3). The MPEG formats reduce file size significantly without sacrificing audio quality.

Speaker

Almost all sound cards support MIDI, a standard for representing music electronically. Also, most sound cards are sound blaster-compatible, which means that they can process commands written for a sound blaster card, and I reality it is necessary standard for PC sound.

Sound cards use two basic methods to translate digital data into analog sounds.

i. Frequency Modulation (FM) Synthesis mimics different musical instruments according built-in formulas.

ii. Wavetable Synthesis relies on recordings of actual instruments to produce sound Wavetable synthesis produce more accurate sound, but is also more expensive.

4. PRINTERS

Printers are one of the main output devices. It gives hard or printed output. The output we get through this device is called as hard copy output. There are different types of printers. They are classified according to the speed and the use of technology. Printers are basically categorized into tow types. They are Impact and Non-Impact Printers.

a. Impact Printers

An impact printer is like a typewriter and the characters are formed by physically striking the type device against an inked ribbon. Impact printers can produce a page, a line, or character at a time.

They can again be classified into two types according to their mechanism. They are:

i. Character Printers: The printer which are able to print a character at a time is known as character printers. Examples of character printers are:

Daisy wheel

1. Daisy Wheel Printer

The print element of Daisy Wheel printer is a flat spoke wheel with characters embossed along the outer edge of the spokes. The daisy wheel print element rotates to the appropriate character which is then struck with a hammer. Most of the word processor use a daisy wheel printer for the output. Type fonts in daisy wheel printer can be changed conveniently by changing the daisy wheel element.

Dot Matrix Printer

2. Dot Matrix

Dot Matrix is the basis of printing mechanism in Dot-Matrix printers. The dot matrix is formed by arranging a number of small rods in a specific number of rows and columns. The number of rows and the number of columns in the dot-matrix may vary from printer to printer. No type elements requires to be shifted in this; in order to print a character it is only necessary to strike the corresponding configuration of rods.

ii. Line Printers

The type of printer that prints a whole line at a time is known as line printer. They are of also two types. They are:

Drum Printer

1. Drum Printer:

The print element is a drum or a cylinder with a complete set of characters engraved of it around the drum. Each band has one each of the different characters and there are as many bands along the cylinder length as the number of characters the printer can print in one line. Each position has its own hammer. To print a character, the drum rotates to the appropriate position and the hammer strikes the paper against the ribbon and the type element.

2. Chain Printer

The print element in a chain printer is a chain that rotates horizontally in front of paper. Several set of characters are located on the chain. As a drum printer hammer are positioned on the other side of the paper. The chain is rotating and when the appropriate printer is one of the fastest impact printers.

b. Non Impact Printers

Non impact printers are the printers that print by spraying ink, by laser beam or by using heat. They are more reliable, faster and quieter than impact printers.

Inkjet Printers

i. Ink Jet Printers

Ink jet printers also called bubble jet printers prints by spraying tiny ink in the paper. It works by forming an image that is composed of tiny dots. Inkjet printers spray small droplets of ink rapidly from tiny nozzles onto the surface of paper to form characters. It can also print in color, which makes it popular choices for home users.

How Laser Printer Works

ii. Laser Printers

Laser printer also known as page printer produce very high quality output of text or data generated from a word processing or a data processing system. It uses laser beam to create the image. Under the printer’s computerized control, a laser beam creates electrical charges on a rotating print drum. These charges attract toner, which is transferred to the paper and fused to its surface by a heat process. In contrast to ink jet, laser printers prints faster, some can crank out18 or more pages per minute.

Thermal Printer

iii. Thermal Printers

Thermal printers use electrical heat to generate an image on specially treated paper. The printer uses pins to produce an image, but rather than striking the pins against a ribbon to mark the paper as does a wire-pin dot-matrix printer, it heats the pins and brings them into gentle contact with the paper. The special coating on the paper discolors when it is heated. The thermal printers are inexpensive and are used in most calculators and fax machines. They produce low quality print and the paper tends to curl and fade after a few weeks or months.