Input Devices

Input Devices

1. Mouse

   • Works by detecting movement on two axes (x, y) The handheld mouse uses a ball which touches two metal wheels When the ball is moved over a surface it moves the two wheels A touchpad uses the capacitance of a finger to detect where the finger is in relation to the axes

2. Keyboard

   • QWERTY keyboards are used to enter text into a computer They continually scan all the keys to see if any key or key combination has been pressed It then sends the jet or key combination to the cimputer using standard code like ASCII code or unicode 

3. Bar Code Reader

4. Scanners

   • They capture a picture, printed text, handwriting or a solid object It then produces a digital representation which can be stored on a computer

5. Flatbed Scanner

   • It shines a bright light from underneath a document The light sources is moved slowly from one end of the scanner to the other with an array or red, blue and green lights detecting sensors - this picks up all the reflected light The light is converted into an electrical signal - which is made up of res, blu and green levels

6. Fingerprint Scanner

   • It is security device that takes and image of a finger, by using light sensors, picture imaging, or electrical currents to map skin contours They are often used as security devices They can be built into a computer of peripheral which is attached using a USB port 

7. Retina Scanner

   • They use low-energy infrared light sourse that is directed onto the retina Photoelectric detectors convert the light to an electric signal It is then decoded into a form that the cimputer can compare it with a stored image Each persons retina is unique and therefore is very secure from identification This process is similar to iris scanning, however an iris is not unique and therefore not as secure

8. Optical Mark Reader

   • It reads the intensity of light reflected back uses photoelectric sensors If it detects a difference in light intensity there has been a mark made This can be used for multiple choice tests and lottery tickets

9. Optical Character Reader

   • They import the image like a flatbed scanner - it then uses the software to read the characters by matching it with sample characters, this is often used for mail order forms and gas bills the systems are used to automate postal sorting - they capture an image of the address on the envelop extract the postcode then print the postcode in a machine-readable code of phosphor dots are used in the rest of the automatic sorting process It takes a fraction of a second as the letter passes through the machine

10. Smart Card Reader

    • It has an integrated circuit chip containing a microprocessor - a small amount of ROM, a small amount of EPROM, a small amount of RAM and a computer bus system Power is provided by the smart card reader when the card is inserted The chip acts as a normal computer holding programs to be executed in the ROM It is used in application such as credit and debit cards 

11. RFID Reader

    • Uses radio frequencies to transmit data There is no electrical contact to transfer data A RFID system has a transponder and a reader The transponder is located on the object to be indentified  The data capacity of a transponder is normally several kilobytes - 1 but transponders can only tell whether they are present or not It can be used for opening gates and oyster cards

12. Touch Sensitive Screen

    • This is a visual display unit allows the user to interact with the application The user touches regions of the screen to perform certain functions One method uses a specially adapted screen with a region just in front of the screen criss-crossed by horizontal and vertical beams of infrared light - invisible to the naked eye When the screen is pressed some of these beams are broken and by using a series of photoelectric sensors - it is possible to work out where the finger is pressing  An electronic circuit connected to these sensors tells the computer the coordinated This is very common in phones and hand held devices

13. Graphics Tablet

    • Consists of a pen/stylus and a board connected to a PC  When the pen is pressed to the board the pen is activated and the movements of the tip are recorded by the computer The board contains electronics to detect the position of the pen tip. This can be used to create drawing in a graphics package

14. Voice Recognition

    • A computer can be trained to recognise a persons voice and to turn speech into text using microphone, sound card and appropriate software This system can also be used to issue commands

15. Digital Still Camera

    • It captures an image and puts into electronic form which a computer can read The image is produces by using either a charge-coupled device or a CMOS image sensor to sense light intensities 

16. Magnetic Stripe Reader

    • Information is encoded magnetically in a stripe on the back of a plastic or cardboard card The stripe is made of magnetic particles encased in a tape made of plastic A stripe can store up to 2 KBThey are used in applications such as credit and debit cardsThe card is read by a reader which picks up the magnetic encoding and decodes the information held on the card