VARIOUS TYPES OF input DEVICES

VARIOUS TYPES OF input DEVICES

Various types of I/O devices are used in the modern computer. Here in this chapter we will familiarize ourselves with the various types of I/O devices. Here is the list of main devices with which we will introduce ourselves

1. Input devices

a. Keyboard

b. Pointing Devices (Mouse,Trackball,Joystic)

c. Scanners

d. Web camera

e. Barcode reader

f. Touch Screen

g. Biometric reader

2. Output devices

a. Monitors

b. Printers

INPUT DEVICES

KEYBOARD

Keyboards are input devices which translates keystrokes into letters or numbers. Three type of

basic key is available on the keyboard. They are

• Alphabet keys

• Numerical keys

• Special function keys

The keyboard is used to type information into the computer or input information. There are many different keyboard layouts and sizes with the most common for Latin based languages being the QWERTY layout (named for the first 6 keys). The standard keyboard has 101 keys. Notebooks have embedded keys accessible by special keys or by pressing key combinations (CTRL or Command and P for example). Ergonomically designed keyboards are designed to make typing easier.

Some of the keys have a special use. There are referred to as command keys. The 3 most common are the Control or CTRL, Alternate or Alt and the Shift keys though there can be more (the Windows key for example or the Command key). Each key on a standard keyboard has one or two characters. Press the key to get the lower character and hold Shift to get the upper.

Keyboards can be categorized on the basis of design in following type

• Dome Switch keyboard

• Capacitive keyboard

• Mechanical Switch keyboard

• Hall Effect keyboard

• Membrane keyboard

Further there are some special featured keyboards which are as follows

• Ergonomic keyboards

• USB Keyboards with hubs

• Multi media and web enabled keyboards

• Wireless keyboards

Interfacing of keyboard-

Following type of interface is available to connect keyboard with device

• DIN5 connectors

• PS/2 Connectors

• Wireless(Blutooth,Infrared)

• USB

MOUSE

Mouse is a pointing device which translates movement on a horizontal surface into movement of a pointer on the screen. Basically there are two methods of translation and they are opto mechanical and optical. This device is used for GUI application. Mainly there are three type of mouse

Mechanical

Optical

Opto - mechanical

There are some special feature pointing device/mouse which are developed as per various requirement of the application and they are

• Cordless

• Foot mouse

• J mouse

• Joystick

• Touch pad

• Trackball

• Track Point

• Wheel mouse

Various interfaces that is used with mouse

• Serial

• PS/2

• USB

• Wireless

Optical scanners do not distinguish text from illustrations; they represent all images as bit maps.

Therefore, you cannot directly edit text that has been scanned. To edit text read by an optical scanner,

you need an optical character recognition (OCR) system to translate the image into ASCII characters.

Most optical scanners sold today come with OCR packages.

Scanners differ from one another in the following respects:

Scanning technology: Most scanners use charge-coupled device (CCD) arrays, which consist of tightly packed rows of light receptors that can detect variations in light intensity and frequency. The quality of the CCD array is probably the single most important factor affecting the quality of the scanner. Industry-strength drum scanners use a different technology that relies on a photomultiplier tube (PMT), but this type of scanner is much more expensive than the more common CCD -based scanners.

Resolution: The denser the bit map, the higher the resolution. Typically, scanners support

resolutions of from 72 to 600 dpi.

Bit depth: The number of bits used to represent each pixel. The greater the bit depth, the more colors or grayscales can be represented. For example, a 24-bit color scanner can represent 2 to the 24th power (16.7 million) colors. Note, however, that a large color range is useless if the CCD arrays are

capable of detecting only a small number of distinct colors.

Size and shape: Some scanners are small hand-held devices that you move across the paper. These hand-held scanners are often called half-page scanners because they can only scan 2 to 5 inches at a time. Hand-held scanners are adequate for small pictures and photos, but they are difficult to use if you need to scan an entire page of text or graphics.

Scanners can be categorized as following types

• Sheet -fed Scanners

• Flatbed Scanners

• Overhead Scanners

Larger scanners include machines into which you can feed sheets of paper. These are called sheet-fed scanners. Sheet-fed scanners are excellent for loose sheets of paper, but they are unable to handle bound documents.

A second type of large scanner, called a flatbed scanner, is ike a photocopy machine. It consists of a board on which you lay books, magazines, and other documents that you want to scan. Overhead scanners (also called copy board scanners) look somewhat like overhead projectors. You place documents face-up on a scanning bed, and a small overhead tower moves across the page.

WEB CAMERA

Web camera commonly known as Webcams is a digital input device in which a digital camera of low resolution (generally) is attached with the computer for use with web. This is generally used for video conferencing/video chat on the net. They are video capturing devices connected to computers or computer networks, often using USB

TOUCH SCREEN

A touch screen is a computer display screen that is also an input device. The screens are sensitive to pressure; a user interacts with the computer by touching pictures or words on the screen. A basic touch screen has three main components: a touch sensor, a controller, and a software driver. The touch screen is an input device, so it needs to be combined with a display and a PC or other device to make a complete touch input system.

There are three types of touch screen technology:

• Resistive: A resistive touch screen panel is coated with a thin metallic electrically conductive and resistive layer that causes a change in the electrical current which is registered as a touch event and sent to the controller for processing. Resistive touch screen panels are generally more affordable but offer only 75% clarity and the layer can be damaged by sharp objects. Resistive touch screen panels are not affected by outside elements such as dust or water.

• Surface wave: Surface wave technology uses ultrasonic waves that pass over the touch screen panel. When the panel is touched, a portion of the wave is absorbed. This change in the ultrasonic waves registers the position of the touch event and sends this information to the controller for processing. Surface wave touch screen panels are the most advanced of the three types, but they can be damaged by outside elements.

BARCODE READER

The machine-readable representation of the UPC (Universal Product Code) is known as Bar code and the device which reads it is known as bar code reader.

` Bar codes are read by a scanner that passes over the code and registers the UPC. The width of each black line and the subsequent white space between each line coincides with the numbers of the UPC.

It consists of a light source, a lens and a light sensor translating optical impulses into electrical ones. Additionally, nearly all barcode readers contain decoder circuitry analyzing the barcode's image data provided by the sensor and sending the barcode's content to the scanner's output port.

The reader types can be distinguished as follows:

• Pen type readers

Pen type readers consist of a light source and a photodiode that are placed next to each other in the tip of a pen or wand.

• Laser scanners

Laser scanners work the same way as pen type readers except that they use a laser beam as the light source and typically employ either a reciprocating mirror or a rotating prism to scan the laser beam back and forth across the bar code. As with the pen type reader, a photodiode is used to measure the intensity of the light reflected back from the bar code. In both pen readers and laser scanners, the light emitted by the reader is tuned to a specific frequency and the photodiode is designed to detect only this

modulated light of the same frequency.

• CCD Readers

CCD readers (also referred to as LED scanner) use an array of hundreds of tiny light sensors lined up in a row in the head of the reader. Each sensor can be thought of as a single photodiode that measures the intensity of the light immediately in front of it. Each individual light sensor in the CCD reader is extremely small and because there are hundreds of sensors lined up in a row, a voltage pattern identical to the pattern in a bar code is generated in the reader by sequentially measuring the voltages across each sensor in the row. The important difference between a CCD reader and a pen or laser scanner is that the CCD reader is measuring emitted ambient light from the bar code whereas pen or laser scanners are measuring reflected light of a specific frequency originating from the scanner itself.

• Camera-Based Readers

2D imaging scanners are the fourth and newest type of bar code reader currently available. They use a small video camera to capture an image of a bar code. The reader then uses sophisticated digitalimage processing techniques to decode the bar code.

• Omni-Directional Barcode Scanners

There are a range of different Omni-directional units available which can be used for differing scanning applications, ranging from retail type applications with the barcodes read only a few centimeters away from the scanner to industrial conveyor scanning where the unit can be a couple of meters away or more from the code. Omni-directional scanners are also better at reading poorly printed, wrinkled, or even torn barcodes.

ELECTRONIC SIGNATURE PAD

An electronic signature is a “sound, symbol, or process, logically associated with a document” such that it is:

• Unique to each user

• Under the sole control of the signer

• Linked to a document in such a way as to prevent tampering, and

• Capable of being authenticated

Several different methods and technologies exist for attaching “electronic signatures” to documents according to these stipulations. Two common types of signature technology that are widely available yet differ greatly in substance are PIN/Password signature stamps and digitized handwritten signatures.

A PIN/Password stamp inserts a single fixed signature image into each signed document when a user types a password or PIN. Digitized handwritten signatures are captured with special pen-and-tablet systems that convert a user’s signature accurately into pen events or a summary image. These methods have different ramifications for security and authentication.The use of any pen-and-tablet signature technology may seem to be the logical replacement for traditional “wet” ink-on-paper signatures; there are several issues to consider when choosing a system for your business. Signature capture hardware

manufacturers have their own specifications, data formats, and software methodologies that affect security, authentication, and legality.Electronic signature capture is a technology for signing electronic document files with a handwritten signature. The use of this technology allows for the complete elimination of the mailing,storage, filing, copying, and retrieval of paper documents. This saves business time and money.

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