Input / Output Devices

• I.T. for Management

Chapter 3

Input/Output Devices

Keyboard
The keyboard is much like the QWERTY
typewriter keypad
A computer keyboard contains an Array
of switches, each of which sends the PC a
unique signal when pressed
The keyboard has a keyboard buffer
memory where it stores


Keyboard
Types of keys
Alphanumeric
Function keys
Curser & screen control
General control
…….Cont


Keyboard
Merits:
keyboard is very familiar means of inputs of
data.It has substantial amount of original text It is
mail tool for data entry keyboard offers special
keys for ex.to connect internet or launch browser
etc.
Demerits: A keyboard is relatively slow input
device.A keyboard can strain eyes & hands


Mouse
The mouse is a device which is used to
translate the motion of your hand into the
signals that the computer can use
Classification is based on types of 3 keys
Either2 , 3 or wheel type
Based on port it is connected Serial USB
Based on technology Mechanical,optical


Mouse
The mouse is a device which is used to translate
the motion of your hand into the signals that the
computer can use
A Tracker ball is a round ball which when
rotated detects the motion and converts it into a
relative shift of the cursor on the screen
……………Cont


Inside Mouse (back)
Two sensors on each wheel allow the
direction to be detected


Inside mouse(front)


Optical Mouse
A typical optical encoding disk: This
disk has 36 holes around its outer
edge.


Tracker ball
A Tracker ball is a round ball which
when rotated detects the motion and
converts it into a relative shift of the
cursor on the screen
Tracker ball is easier movements,no
need to move entire hand
Less desk space required


Monitors
A Monitors refers to an output device
used to render visual information
Types of monitors are :
Gray scale,
Color,
Analog & Digital
Flat panel display
………….. Cont


Monitors
Display Technologies used
– Cathode Ray Technology
– Liquid Crystal Displays
– Plasma displays
– Thin film Transistors

……….. Cont


Monitors
A CRT monitor contains millions of tiny red,
green, and blue phosphor dots that glow
when struck by an electron beam that
travels across the screen to create a
visible image. The illustration below
shows how this works inside a CRT.

……….cont


Monitors

The terms anode and cathode are used in
electronics as synonyms for positive and
negative terminals. For example, you
could refer to the positive terminal of a
battery as the anode and the negative
terminal as the cathode.
……..cont


Monitors


Scanners
The basic principle of a Scanners
is to analyze an image and process
it in same way
The image Capture will allow you
to save information to a file on
your computer.
………. Cont


Scanners
Types of Scanners
– Flatbed :Flatbed scanners, also called
desktop scanners, are the most versatile
and commonly used scanners. In fact, this
article will focus on the technology as it
relates to flatbed scanners
– Sheet bed Sheet-fed scanners are similar to
flatbed scanners except the document is
moved and the scan head is immobile. A
sheet-fed scanner looks a lot like a small
portable printer.


Scanners
Types of Scanners
Handheld scanners
– use the same basic technology as a flatbed
scanner, but rely on the user to move them
instead of a motorized belt. This type of
scanner typically does not provide good
image quality. However, it can be useful for
quickly capturing text.
– ………….Cont


Scanners
Types of Scanners
Drum scanners are used by the publishing
industry to capture incredibly detailed
images. They use a technology called a
photo multiplier tube (PMT). In PMT, the
document to be scanned is mounted on a
glass cylinder. At the center of the cylinder
is a sensor that splits light bounced from
the document into three beams. Each beam
is sent through a color filter into a photo
multiplier tube where the light is changed
into an electrical signal


Scanners
Parts of a typical flatbed scanner include:
• Charge-coupled device (CCD) array
• Mirror Scan head
• Glass plate Lamp ,Lens ,Cover
• Filters
• Stepper motor Stabilizer bar Belt
• Power supply Interface port(s)
• Control circuitry


Scanners
What to look for:
1. Scanners vary in resolution &
sharpness
2. Most of the scanners have a
hardware resolution of atleast
300*300 dots per inches
3. Physical dimension
4. Paper path specifically in case of
sheet fed


How Scanner works
– 1. The document is placed on the glass plate
and the cover is closed. The inside of the
cover in most scanners is flat white,
although a few are black.
– 2. The cover provides a uniform background
that the scanner software can use as a
reference point for determining the size of
the document being scanned.
– 3. Most flatbed scanners allow the cover to
be removed for scanning a bulky object,
such as a page in a thick book.


How Scanner works
• A lamp is used to illuminate the document.
The lamp in newer scanners is either a cold cathode
fluorescent lamp (CCFL) or a xenon lamp, while older
scanners may have a standard fluorescent lamp.

How Scanner works
The entire mechanism (mirrors, lens,
filter and CCD array) make up the scan
head. The scan head is moved slowly
across the document by a belt that is
attached to a stepper motor.
The scan head is attached to a stabilizer
bar to ensure that there is no wobble or
deviation in the pass. Pass means that
the scan head has completed a single
complete scan of the document.

How Scanner works
• The image of the document is reflected
by an angled mirror to another mirror. In
some scanners, there are only two
mirrors while others use a three mirror
approach. Each mirror is slightly curved
to focus the image it reflects onto a
smaller surface.
• The last mirror reflects the image onto
a lens. The lens focuses the image
through a filter on the CCD array.

How Scanner works
The filter and lens arrangement vary
based on the scanner. Some scanners
use a three pass scanning method.
Each pass uses a different color filter
(red, green or blue) between the lens
and CCD array.
After the three passes are completed, the
scanner software assembles the three
filtered images into a single full-color
image.


Touch screen
A Touch screen is an assembly that is
mounted in front of a video display
It is activated by touching the selected area on
the display that indicates the desire
function,with stylus or finger
There are three basic systems that are used to
recognize a person's touch:
Resistive
Capacitive
Surface acoustic wave
……………. Cont

Touch screen
The resistive system consists of a normal
glass panel that is covered with a conductive
and a resistive metallic layer. These two layers
are held apart by spacers, and a scratch-
resistant layer is placed on top of the whole
setup.
An electrical current runs through the two
layers while the monitor is operational. When a
user touches the screen, the two layers make
contact in that exact spot. The change in the
electrical field is noted and the coordinates of
the point of contact are calculated by the
computer. ………………… Cont.

Touch screen
Once the coordinates are known, a
special driver translates the touch into
something that the operating system
can understand, much as a computer
mouse driver translates a mouse's
movements into a click or a drag.
In the capacitive system, a layer that
stores electrical charge is placed on the
glass panel of the monitor.
…………. Cont.

Touch screen
When a user touches the monitor with his or
her finger, some of the charge is transferred to
the user, so the charge on the capacitive layer
decreases.
This decrease is measured in circuits located
at each corner of the monitor. The computer
calculates, from the relative differences in
charge at each corner, exactly where the touch
event took place and then relays that
information to the touch screen driver
software.

…………. Cont.

Touch screen
One advantage that the capacitive
system has over the resistive system is
that it transmits almost 90 percent of
the light from the monitor
Whereas the resistive system only
transmits about 75 percent. This gives
the capacitive system a much clearer
picture than the resistive system
…………. Cont.

Touch screen
On the monitor of a surface acoustic wave
system, two transducers (one receiving and
one sending) are placed along the x and y axes
of the monitor's glass plate.
Also placed on the glass are reflectors -- they
reflect an electrical signal sent from one
transducer to the other. The receiving
transducer is able to tell if the wave has been
disturbed by a touch event at any instant, and
can locate it accordingly.
…………. Cont.

Touch screen

The wave setup has no metallic layers on the screen,
allowing for 100-percent light throughput and perfect image
clarity. This makes the surface acoustic wave system best
for displaying detailed graphics (both other systems have
significant degradation in clarity).

Another area in which the systems differ is in which stimuli
will register as a touch event. A resistive system registers a
touch as long as the two layers make contact, which means
that it doesn't matter if you touch it with your finger or a
rubber ball. A capacitive system, on the other hand, must
have a conductive input, usually your finger, in order to
register a touch.
…………. Cont.

Types of Touch screen
Visi –Touch
Dust Proof
Kiosk touch
Bevel touch
State touch
Antiglare

Touch screen
Technologies used
– Analogue resistive
– Capacitive
– Scanning Infrared
– Surface Acoustic Wave

Printer
Types of Printer
Impact
Dot matrix
Daisy Wheel
Line
Non Impact
Inkjet
Thermal
Laser
Dye Sublimation
Solid ink

Dot matrix Printer
A type of printer that produces characters and
illustrations by striking pins against an ink ribbon to print
closely spaced dots in the appropriate shape.

Dot-matrix printers are relatively expensive and do not
produce high-quality output.

However, they can print to multi-page forms (that is,
carbon copies), something laser and ink-jet printers
cannot do. …………Cont

Dot-matrix Printer

Dot-matrix printers vary in two important characteristics:
· speed: Given in characters per second (cps), the speed can
vary from about 50 to over 500 cps. Most dot-matrix printers
offer different speeds depending on the quality of print
desired.
· print quality: Determined by the number of pins (the
mechanisms that print the dots), it can vary from 9 to 24.
The best dot-matrix printers (24 pins) can produce near
letter-quality type, although you can still see a difference if
you look closely.
In addition to these characteristics, you should also consider
the noise factor. Compared to laser and ink-jet printers, dot-
matrix printers are notorious for making a racket.

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 or daisy wheel printer,
letters are drawn out of a dot matrix, and thus,
varied fonts and arbitrary graphics can be
produced. Because the printing involves
mechanical pressure, these printers can create
carbon copies and carbonless copies.

Dot-matrix Printer

Digital then broadened the basic LA36 line onto
a wide variety of dot matrix printers including:
•LA180 -- 180 c/s line printer
•LS120 -- 120 c/s terminal
•LA120 -- 180 c/s advanced terminal
•LA34 -- Cost-reduced terminal
•LA38 -- An LA34 with more features
•LA12 -- A portable terminal

Daisywheel Printer

A daisy wheel printer is a type of
computer printer that produces
high-quality type, and was often referred to during the
1980s as a letter-quality printer
(in contrast to high-quality dot matrix printers, capable
of so-called near letter quality (NLQ) output).
There were also, and still are, daisy wheel
typewriters, based on the same principle.
The system used a small wheel with each letter printed
on it in raised metal or plastic. The printer turns the
wheel to line up the proper letter under a single pawl
which then strikes the back of the letter and drives it
into the paper.

Daisywheel Printer
In many respects the daisy wheel is similar to a standard
typewriter in the way it forms its letters on the page,
differing only in the details of the mechanism (daisy
wheel vs. typebars or the typeball used on IBM Selectric
typewriters).
Daisy wheel printers were fairly common in the 1980s,
but were always less popular than dot matrix printers
(ballistic wire printers) due to higher cost and the dot-
matrix's ability to print graphics and different fonts. With
the introduction of high-quality laser printers and inkjet
printers in the later 1980s, daisy wheel systems quickly
disappeared but for the small remaining typewriter
market

Laser Printer
The term laser printer is a bit more mysterious -- how can a
laser beam, a highly focused beam of light, write letters and
draw pictures on paper?
In this article, we'll unravel the mystery behind the laser
printer, tracing a page's path from the characters on your
computer screen to printed letters on paper. As it turns out,
the laser printing process is based on some very basic
scientific principles applied in an exceptionally innovative
way.

Laser Printer
The Basics: Static Electricity
The primary principle at work in a laser printer is static
electricity, the same energy that makes clothes in the dryer
stick together or a lightning bolt travel from a thundercloud to
the ground.

Static electricity is simply an electrical charge built up on an
insulated object, such as a balloon or your body.

Since oppositely charged atoms are attracted to each other,
objects with opposite static electricity fields cling together.
….. Cont

Laser Printer
A laser printer uses this
phenomenon as a sort of
"temporary glue." The core
component of this system is the
photoreceptor, typically a
revolving drum or cylinder.
This drum assembly is made
out of highly photoconductive
material that is discharged by
light photons.

Laser Printer

Inkjet Printer

An inkjet printers simply spray ink in a series of dots
to form characters.
Print head assembly Print head - The core
of an inkjet printer, the print head contains a
series of nozzles that are used to spray drops of
ink.

Inkjet Printer

Stepper motors like this one
control the movement of
most parts of an inkjet
printer.

Inkjet Printer

Belt - A belt is
used to attach the print head
assembly to the stepper
motor.

Stabilizer bar -
The print head assembly uses
a stabilizer bar to ensure that
movement is precise and
controlled.

Inkjet Printer

Paper feed assembly

Paper tray/feeder - Most inkjet printers have a tray
that you load the paper into. Some printers dispense with
the standard tray for a feeder instead.

he feeder typically snaps open at an angle on the back of
the printer, allowing you to place paper in it. Feeders
generally do not hold as much paper as a traditional paper
tray.

Inkjet Printer

§ Rollers - A set of rollers pull the paper in
from the tray or feeder and advance the paper when the
print head assembly is ready for another pass.

The rollers move the paper through the printer

Inkjet Printer

Paper feed stepper motor - This stepper motor
powers the rollers to move the paper in the exact increment
needed to ensure a continuous image is printed.

Power supply - While earlier printers
often had an external transformer, most printers sold today
use a standard power supply that is incorporated into the
printer itself.

Control circuitry - A small but
sophisticated amount of circuitry is built into the printer to
control all the mechanical aspects of operation, as well as
decode the information sent to the printer from the
computer

Inkjet Printer

The mechanical operation of the printer is controlled by a
small circuit board containing a microprocessor and
memory.

Inkjet Printer

Interface port(s) - The parallel port is still
used by many printers, but most newer printers
use the USB port.
A few printers connect using a serial port or
small computer system interface (SCSI) port.

While USB taking over, many printers still use a parallel port

Thermal Printer

In the Thermal printers a film coated synthetic
paper
and miniature heat element embedded rollers are
used.
The film turns black when it gets heated
These are normally used for high quality short
life printing
It fades after 6 months or 1year

Web Camera
A simple Web cam consists of a digital
camera attached to a computer
Typically through the USB port.
The camera part of the Web cam setup
is just a digital camera -- there's really
nothing special going on there. The
"Web cam" nature of the camera
comes with the software

Web Camera
Web cam software "grabs a frame" from the
digital camera at a preset interval (for
example, the software might grab a still
image from the camera once every 30
seconds) and transfers it to another location
for viewing. If you're interested in using your
Web cam for streaming video, you'll want a
Web cam system with a high frame rate.
Frame rate indicates the number of pictures
the software can grab and transfer in one
second. For streaming video, you need a
minimum rate of at least 15 frames per
second (fps), and 30 fps is ideal.

Input/Output Devices PDA’s
Personal Digital Assistance (PDA) is a tiny,fully
functional computer that you can hold in one
hand.
A PDA can hold your down loaded emails &
music
Palm PDAs
Most Palm devices are made by palm One,
which offers the Zire and Tungsten product
lines. The company formed in 2003 when
Palm Computing acquired Handspring, Inc.
Sony, which produced the Palm-based CLIE,
stopped producing PDAs in 2005.


nown for their ease of use, Palm OS PDAs have:

A vast library of third-party
applications (more than 20,000) that you can add
to the system (most devices come bundled with
e-mail, productivity, and multimedia software)

An updated version of the Graffiti
handwriting-recognition application

Synchronization with both Windows
and Macintosh computers using the Palm
Desktop

Smaller displays than Pocket PCs
to accommodate a dedicated Graffiti area on the


A cellular service provider to handle phone
service (As with cell phones, you typically purchase
a cellular plan and smart phone from the service
provider.)

Internet access through cellular data networks

Various combinations of cell phone and PDA
features, depending on the device (for example, not
all smart phones offer handwriting-recognition
capabilities)

Bar Code

You can see that the UPC symbol printed on a
package has two parts:
• The machine-readable bar code
• he human-readable 12-digit UPC number
BYG Publishing's manufacturer identification
number is the first six digits of the UPC number --
639382. The next five digits -- 00039 -- are the item
number. A person employed by the manufacturer,
called the UPC coordinator, is responsible for
assigning item numbers to products, making sure
the same code is not used on more than one
product, retiring codes as products are removed
from the product line, etc.

Bar Code
In general, every item the manufacturer
sells, as well as every size package and
every repackaging of the item, needs a
different item code. So a 12-ounce can of
Coke needs a different item number than a
16-ounce bottle of Coke, as does a 6-pack of
12-ounce cans, a 12-pack, a 24-can case,
and so on. It is the job of the UPC
coordinator to keep all of these numbers
straight!
The last digit of the UPC code is called a
check digit.

• I.T. for Management

End of Chapter 3

Input / Output Devices

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Input / Output Devices