Output Devices

Types of Monitor (Color) :

1. Monochrome Color: Used two color One for foreground & another for background (color may be black & white)
2. Gray Scale: Used two color one for foreground & another for background but used different gray shadow in place of black (color may be gray & white)
3. Color: Display more than 1 million color (color is red, green & blue)

Types of Monitor (Signal):

1. Analog: Analog monitor provide display using analog signal.
2. Digital: Digital monitor provide display using display signal.

Attribute of Monitor :

Pixels:-

A pixel is the smallest element of a video image, but not the smallest element of a monitor’s screen. Since each pixel must be made up of three separate colors, there are smaller red, green, and blue dots on the screen that make up the image. The term dot is used to refer to these small elements that make up the displayed image on the screen.

A pixel is the smallest element in monitor that according display image on monitor.

Resolution:-

The display resolution of a display device is the number of distinct pixels in each dimension that can be displayed.

The term is most often used to describe monitors, printers, and bitmapped graphic images. In the case of dot-matrix and laser printers, the resolution indicates the number of dots per inch.

In monitors, the screen resolution signifies the number of dots (pixels) on the entire screen. For example, a 640-by-480 pixel screen is capable of displaying 640 distinct dots on each of 480 lines, or about 300,000 pixels. This translates into different dpi measurements depending on the size of the screen. For example, a 15- inch VGA monitor (640×480) displays about 50 dots per inch.

(640×480), (800×600), (1024×768), (1152×720), (1440×900)

Dot Pitch:-

Also called phosphor pitch, a measurement that indicates the diagonal distance between like-colored phosphor dots on a display screen. Measured in millimetres, the dot pitch is one of the principal characteristics that determine the quality of display monitors. The dot pitch of color monitors for personal computers ranges from about 0.15 mm to 0.30 mm.

Refresh Rate:-

The refresh rate is the number of times a display’s image is repainted or refreshed per second. The refresh rate is expressed in hertz. The refresh rate for each display depends on the video card used.

The refresh rate is the number of times in a second that display hardware draws the data in CRT Monitor approx 30 to 60 time refresh rate required.

Interlaced Monitor vs. Non Interlaced Monitor:-

Interlacing is a display technique that enables a monitor to provide more resolution inexpensively. With interlacing monitors, the electron guns draw only half the horizontal lines with each pass (for example, all odd lines on one pass and all even lines on the next pass). Because an interlacing monitor refreshes only half the lines at one time, it can display twice as many lines per fresh cycle, giving it greater resolution. Another way of looking at it is that interlacing provides the same resolution as no-interlacing, but less expensively. A shortcoming of interlacing is that the reaction time is slower, so programs that depend on quick refresh rates (animation and video, for example), may experience flickering or streaking.

Video Standard:-

To display graphics a display screen must have a video display adapter. A video display adapter, also called a graphic adapter card, it is a circuit board that determines the resolution, number of colors and how fast images appear on the display screen. Video display adaptors come with their own memory chips that determine how fast card processes images and how many colors it can display.

Speakers

• A speaker or speaker system converts an electrical signal to sound. A speaker is a term used to describe the user who is giving vocal commands to a software program.
• Speakers are popular output devices used with computer systems. They receive audio input from the computer’s sound card and produce audio output in the form ofsound waves. Most computer speakers are active speakers, meaning they have an internal amplifier which allows you to increase the volume, or amplitude, of the sound.
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• When computers were originally released they had on-board speakers that generated a series of different tones and beeps. As multimedia and games became popular, higher quality computers speakers began to be released that required additional power. Because computer sound cards are not powerful enough to power a nice set of speakers today’s speakers are self-powered, relatively small in size, and contain magnetic shielding.
• These devices are used to produce sound from the computer system. The soundcard is a card installed in the tower case of the computer. Its role is to convert the signal coming out of the computer to a format that can be reproduced by the external speakers.
• The Audio output is the ability of the computer to output sound. Two components are needed: Sound card – Plays contents of digitized recordings, Speakers – Attached to sound card.
• Speakers usually come in pairs, which allow them to produce stereo sound from two separate audio channels.

Printer

Printers are the most popular output devices. They provide information in a permanent readable form. They produce printed output of result, programs and data. Printers used with computers can be classified as follows:

Impact Printer

An impact printer makes contact with the paper. It usually forms the print image by pressing an inked ribbon against the paper with a hammer like mechanism.

1. Dot Matrix Printer

It is an impact type character printer. They were developed with two objectives: Greater speed and more flexibility.

The images are formed by a print head that is composed of a series of little print hammers that look like the head of pins. These print mechanism moves across the entire print line.

The print head of a dot-matrix printer has as many as 24 pins, which allows a much more precise image to be produced.

The print quality of a dot-matrix printer is inferior to that of a daisy-wheel printer. But dot- matrix printers are generally faster and less expensive than a daisy wheel printer. They also do not have a fixed character but have different sizes of print, special characters and the ability to print graphics such as chart and graphs. [Typical output from a dot matrix printer operating in draft mode. This entire image represents an area of printer output approximately 4.5 cm x 1.5cm (1.75 x 0.6 inches) in size.]

2. Daisy Wheel Printer

It is an impact printer. It is also called letter-quality printers, or character printer or serial printer because they print one character at a time. They produce a very high quality print image because the entire character is formed with a single impact. They are generally used for important business letters, memos, and reports.

It has a print wheel with a set of print character on the outside tips of the flat spokes. To print a specific character, the wheel is spun at a rapid rate. When the desired character spins to the correct position, a print hammer strikes it to produce the output.

3. Chain Printer

They use a rapidly moving chain called a print chain. Each link of the chain is a character font. Instead of a chain, some models of printers use a metal band having raised print characters on it. For each possible print position, there is a print hammer located behind the paper. As the print chain or the band rotates, the properly timed print hammers strike the paper, along with the inked ribbon, against the proper character on the chain/band as it passes.

In order to enhance the speed of chain printers, the character set is repeated several times on the chain. Hence it is not necessary to wait for the chain to make a complete revolution to position the desired character in the correct print position.

4. Band Printer

Band printer is just like a chain printer. It contains fast rotation steel print bands in place of chains. The print band contains a raised character set. Hammers strike the ribbon and the paper against the character to print the character.

5. Drum Printer

A drum printer consists of a solid, cylindrical drum that has raised characters in bands on its surface. There are as many bands as there are printing positions. Each band  contains  all  the  possible characters. The drum rotates at a rapid speed. For each possible print position, that is, opposite to each band of drum, there is print hammer located behind the paper.

These hammers strike the paper, along with the inked ribbon, against the proper character on the drum as it passes. One revolution of the drum is required to print each line. This means all characters on the line are not printed at exactly the same time, but the time required to print the entire line is fast enough to call them line printers.

Non Impact Printer

They do not hit or impact a ribbon to print, they use thermal, electrostatic, Chemical or Inkjet technologies

1. Laser Printer

Laser printer technology uses much less mechanism than impact printing, resulting in much higher speed and easier operation. Laser printers work like a photocopy machine. A laser beam is directed across the surface of a light-sensitive drum and fired as needed to record an image in the form of a pattern of tiny dots. The image is then transferred to the paper, a page at a time, in the same fashion as a copy machine, using a special toner.

2. Ink Jet Printer

Theyprint character byspraying smalldrops of ink onto paper. Specialtype of inkhaving highiron content isused. Droplets of ink are electrically charged after leaving a nozzle. The droplets are then guided to the proper position on the paper by electrically charged deflection plates. Ink-Jet printer produced high quality output because the characters are formed by dozens of tiny ink dots. Moreover, they are quiet and can form any kind of character.

The document printed may contain multiple character styles and a variety of type-sizes. Some models also allow for different colors of ink for multiple color printing. Of course inkjet and other non impact printers cannot produce multiple copies of a document in a single printing, which is possible with impact printers.

Plotter

A plotter is a specialized output device designed to produce high-quality graphics in a variety of colors. There are two basic types of plotters: those that use pens and those that do not. Drum plotters and flatbed plotters both use pens. Electrostatic plotters do not.

• Drum plotter: In a drum plotter, the paper is mounted on the surface of a drum. The drum revolves and the plotter pens are horizontally positioned over the target area. When the paper has rotated to the correct point, the pens are dropped to the surface and moved left and right under program control across the paper as the drum revolve. When the image is complete, the pens are raised from the surface.
• Flatbed plotter: Flatbed plotters are designed so that the paper is placed flat and one or more pens move horizontally and vertically across the paper.
• Electrostatic plotter: Electrostatic plotters use electrostatic charges to create images out of very small dots on specially treated paper. The paper is run through a developer to allow the image to appear. Electrostatic plotters are faster than pen plotters and can produce images of very high resolution.