Computer Input & Output Devices
Computer Input & Output Devices
8.1 Scanner
Computer Input & Output Devices.A scanner is an electronic device that scans printed or handwritten text documents, images, or a particular object to convert them into a digital file format. Most of the scanners use CCD, (charge-coupled device) or CIS, (Contact Image Sensor) as the image sensors. The common types of scanners we see today are flatbed scanners, handheld scanners, sheetfed scanners, etc.Flatbed Scanner
A flatbed scanner is made up of a glass pane and a moving optical CIS or CCD array. The pane is illuminated with the help of bright light planted underneath it. The image which is to be scanned is then placed on the glass pane. The sensor and the source of light move across the glass pane to scan the document and produce its digital copy.Sheetfed Scanner
In sheetfed scanners, the document that is supposed to be scanned is fed into the horizontal or vertical slot provided in the scanner. The vital components of sheetfed scanner are the sheet-feeder, scanning module and calibration sheet. Such scanners are most often used to scan single page documents. It can’t be used to scan thicker objects, like books, which turns out to be its major drawback.Handheld Scanner
A handheld scanner is a small manual scanning device which is moved over the object that need to be scanned. For instance, if a document needs to be scanned, the handheld scanner has to be dragged over the document. Using a handheld scanner can prove to be a cumbersome task, as the hand needs to be steady all the time. Slight movement of the hand can lead to distortion of the image. One of the most utilized handheld scanner is the barcode scanner, typically used in shopping stores to valuate goods.
A flatbed scanner is made up of a glass pane and a moving optical CIS or CCD array. The pane is illuminated with the help of bright light planted underneath it. The image which is to be scanned is then placed on the glass pane. The sensor and the source of light move across the glass pane to scan the document and produce its digital copy.Sheetfed Scanner
In sheetfed scanners, the document that is supposed to be scanned is fed into the horizontal or vertical slot provided in the scanner. The vital components of sheetfed scanner are the sheet-feeder, scanning module and calibration sheet. Such scanners are most often used to scan single page documents. It can’t be used to scan thicker objects, like books, which turns out to be its major drawback.Handheld Scanner
A handheld scanner is a small manual scanning device which is moved over the object that need to be scanned. For instance, if a document needs to be scanned, the handheld scanner has to be dragged over the document. Using a handheld scanner can prove to be a cumbersome task, as the hand needs to be steady all the time. Slight movement of the hand can lead to distortion of the image. One of the most utilized handheld scanner is the barcode scanner, typically used in shopping stores to valuate goods.
Drum: The most efficient and by far the most expensive scanners are the drum scanners. These are used primarily in the publishing industry to digitize the images that appear in books and magazines and are printed on high-quality printing presses. A drum scanner uses a pm(photo-multiplier) tube which is a light sensing device.
8.2 Plotter
The plotter is a graphics output device used to create drawings on paper.
There are two types of plotters
1) Pen plotter
2) Photo plotter
Pen Plotter:-the pen plotter is an electromechanical device. A pen is moved in two dimensions(up/down and left/right) across a paper or film media. Ink pens are normally used in plotters. Color plotters have multiple pens of different colors.
Pen plotters are of many types:
1)Drum plotter:- In a drum plotter, the drum rotates. A pen carriage moves horizontally.
2)Micro grip plotter:- The medium is gripped at the edges and moved back and forth
3)Flatbed plotter:-the pen carriage is moved along both the X and the Y axis. To control the motion in short digital steps. Stepper motors are used.
Photo plotter:- A photo plotter uses fibreoptics technology to produce the image on dry silver paper.
Plotter are available in different sizes A4, A3 etc. there are two methods by which a plotter can be interfaced to a microcomputer: via a serial interface and via a parallel interface.
8.3 Speaker
Speakers are one of the most common output devicesused with computer systems. Some speakers are designed to work specifically with computers, while others can be hooked up to any type of sound system. Regardless of their design, the purpose of speakers is to produce audio output that can be heard by the listener.
Speakers are transducers that convert electromagnetic waves into sound waves. The speakers receive audio input from a device such as a computer or an audio receiver. This input may be either in analog or digital form. Analog speakers simply amplify the analog electromagnetic waves into sound waves. Since sound waves are produced in analog form, digital speakers must first convert the digital input to an analog signal, then generate the sound waves. The sound produced by speakers is defined by frequency and amplitude.
8.4 Microphone
A device for turning acoustic power into electric power is called a microphone. Acoustic power is real sound waves. In other words, it changes sound into an electric signal. These signals are usually sent to an amplifier or recording device. There are many different brands and also different types. Still, they all have one thing in common: they all use a diaphragm.
This diaphragm is a thin part, sometimes made of metal that vibrates when sound goes to the microphone. When the diaphragm shakes, it causes the other parts of the microphone to create signals.
Types of Microphone
Dynamic. The dynamic microphone has a thin diaphragm that is hung by suspension wires. It can break if the wires become damaged. One bad thing about this kind is that because it is less sensitive, it does not pick up sounds as well. But it is great for live performances and recordings that want to sound like live performances.
Carbon is the next kind of microphone. It is an old fashioned design, used on the first telephones. It uses carbon dust which is compressed into the middle of the diaphragm. It makes electrical signals when the sound waves pass through the dust. It is still used on many telephones.
Ribbon is another variety of microphone. Ribbon microphones use a very thin metal wire that is suspended in a magnetic field. When the sound waves or vibrations hit the ribbon, the ribbon vibrates and sends waves through the magnetic field creating electric signals. Ribbon microphones are very sensitive and usually used for special recordings. They are very fragile and can break easily when dropped.
Condenser microphone is the next kind we will learn about. A condenser microphone has a diaphragm separated by carbon that acts as a capacitor. A capacitor is a thing that stores electric energy. So don’t go around touching capacitors. The condenser microphone stores and releases the electronic signals when the diaphragm vibrates. They are very sensitive and are used for voice. If you have a bad voice, don’t use a condenser microphone, because they pickup sounds as they really are.
Crystal change their electronic properties when they change shape. So, if you attach a crystal to a diaphragm, a crystal will create an electric signal when the diaphragm is vibrated.
8.5 Web Camera
A webcam, or web camera, is the loosely used term for any camera that generates images that can be accessed by and displayed on the World Wide Web through a server. A webcam is essentially just a camera that is connected to a computer, either directly or wirelessly, and gathers a series of images for remote display elsewhere. Webcam technology is widely used by all sorts of people for all sorts of different reasons.
In 1991, the first webcam was up and running at Cambridge University’s Computer Science Department, but since then, webcams have crept into homes, businesses, public streets and buildings. Webcams are often used for personal use in the home by parents who want to give distant relatives visual access to their children or want to monitor what goes on in the home while they are at work. People might also use webcams in the home to keep an eye on things while they are out of town or even just to see what their pets do all day. The uses of a webcam are limitless. Businesses often use webcams for video conferencing, and webcam technology is used by numerous other entities to give the public access to a variety of information, from weather and traffic to the feeding habits of the most recently acquired zoo animal. Some schools and day care facilities use a webcam to allow parents to see what their children do at school.
8.6 Joy Stuck
A joystick is an input device commonly used to control video games. Joysticks consist of a base and a stick that can be moved in any direction. The stick can be moved slowly or quickly and in different amounts. Some joysticks have sticks that can also be rotated to the left or right. Because of the flexible movements a joystick allows, it can provide much greater control than the keys on a keyboard.
Joysticks typically include several buttons as well. Most joysticks have at least one button on the top of the stick and another button in the front of the stick for the trigger. Many joysticks also include other buttons on the base that can be pressed using the hand that is not guiding the stick. Joysticks typically connect to your computer using a basic USB or serial port connection and often come with software that allows you to assign the function of each button.
8.7 Light Pen
A light-sensitive input device shaped like a pen, used to draw on the computer screen or to make menu selections. As the tip of the light pen makes contact with the screen, it sends a signal back to the computer containing the x-y coordinates of the pixels at that point. Light pens can be used on any size screen.
Light pens give the user the full range of mouse capabilities, without the use of a pad or any horizontal surface. Users can interact more with the application, in such modes as drag and drop, or highlighting.
Light pens give the user the full range of mouse capabilities, without the use of a pad or any horizontal surface. Users can interact more with the application, in such modes as drag and drop, or highlighting.
8.8 Bar code Reader
A barcode reader (or barcode scanner) is an electronic device for reading printed barcodes. Like a flatbed scanner, 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.
8.9 MODEM
The word modem is an acronym for modulator cum demodulator. A modem is an input/output device used to link a telephone line so as to communicate with another computer. The telephone system transmits voice and data as analog signals.
When a computer sends data to another computer, the modem takes the digital data from the computer, modulates it into analog voltage that can be transmitted over the telephone line. At the receiving end, another modem converts the analog voltage into digital data.
There are two types of modem
1) Internal Modem
2) External Modem
8.9.1 Internal MODEM
Internal modems is a plug-in circuit board that sits inside the computer. It incorporates the serial port on-board. They are less expensive than external modems because they do not require a case, power supply and serial cable. They appear to the communication programs as if they were an external modem for all practical purposes.
8.9.2 External MODEM
Most external modems today are not dial-up modems, but broadband modems. Externalmodems designed for broadband service provide a different kind of Internet connection that is extremely fast, used with high-speed ISPs. Broadband modems typically have transfer rates from 1.5 — 8 mbps (megabytes per second), or higher.
DSL, FiOS, cable and satellite are different flavors of high-speed Internet. Normally ISPs selling broadband Internet access will provide their customers with external modems pre-configured to use with the service. Depending on the contract terms, the external modems might be leased with a small monthly charge, or provided free to use for the duration of the client’s contract. High-speed modems are normally not internal.
External modems used for broadband service can be wired, or wireless. If wireless, a wireless network adapter must be installed in each computer that is to communicate with the modem. These adapters can be PCMCIA, or external devices that attach to the computer via the USB port.
