8.1 Hardware – Input Devices

1. 8.1 Hardware – Input Devices By Ranjit Bassi

2. Mouse • First prototype computer mouse was made by Douglas Englebert using a wooden shell with two metal wheels • It was nicknamed the mouse due to a tail out of the end • Works by detecting movement in the two axes x and y • Wireless mice communicate by using a wireless signal instead of down a wire

3. Keyboard • Used to enter text into a computer system • Components in the keyboard continually scan the rows of keys to detect the pressing of a key or key combination • The components identify which keys have been pressed and send the keys scan code to the computer • Then software in the computer interprets the scan code and converts it into an ASCII code or Unicode code

4. Bar code reader • An electronic device used for reading bar codes • A bar code is a sequence of white and black bars that encodes information • A bar code reader consists of a light source, a lens, photoelectric detectors (photodiodes)and decoder circuitry to analyse the bar code’s image data and generate character codes • The scanner outputs the character codes as a sequence of binary digits for processing by a computer

5. Flatbed Scanner • Uses a glass pane or platen illuminated from beneath a bright light, often xenon or cold-cathode fluorescent • The reflected light from scanner is converted into a equivalent electrical signal • Colour scanners usually contain three rows of sensors with red, blue and green filters (These measure the intensity of the primary colours in the reflected light) • A digitised image of the entire scanned area is created, it can be stored and processed by the computer connected to the computer

6. Fingerprint Scanner • Typically used as a security device • Takes a ‘picture’ of the ridges and valleys in the finger so they can be analysed • The scanner consists of a sensor and decoder circuitry • The scanner analyses the captured image data and outputs it in a electrical form for processing

7. Retina Scanner • Consists of a low energy infrared light source, photoelectric detectors and decoding circuitry • The low energy infrared light is directed onto the retina of the eye • The photoelectric detectors convert the reflected light into an electrical signal • The decoding circuitry outputs an encoded form of the retinal pattern for storage or comparison by a computer

8. Iris Scanner • The scanner uses a camera sensitive to infrared light • An image of the iris is captured and stored electronically • A complex algorithm is applied to the electronic image to create a code of normally 512 bytes • This code is then compared with a database of iris codes to see if there is any match

9. Optical Mark reader • This optically senses marks placed in predefined positions on a form • Form is passed under a light source and the intensity of reflected light is measured and converted by photoelectric sensors into a electrical equivalent • Pencil marks do not reflect as much light as the background colour of the form, this is used to detect the presence of the marks • Optical mark recognition is used for processing multiple-choice answer grids

10. Optical Character reader (OCR) • All of these types of systems use an optical scanner to input images of text then analyse the resulting digital images to recognise the characters. • Some forms such as gas bills are pre-printed with the relevant customer details in a special font that is good for the OCR • Then the forms can be processed automatically when returned • OCR systems are used to automate postal sorting

11. Magnetic Stripe reader • Magnetic stripe readers read information encoded magnetically in a stripe on the back of a plastic or cardboard card • Stripe is composed of magnetic particles encased in tape made of plastic • The orientation of the particles is used to encode binary data • Stripes can normally store up to 2KB of data

12. Smart Card reader • A smart card is a card that holds an integrated chip • The chip contains a microprocessor, little amount of ROM, small amount of EEPROM, little amount of RAM and a computer bus system • Applications are stored in the ROM and EEPROM • The microprocessor executes stored applications • Smart cards have enough processing power to encrypt and decrypt data, so they are used in transactions that require a degree of security against fraud

13. RFID Reader • Radio frequency identification uses radio frequencies to transmit data, a timing signal and energy between a reader and an RFID device • RFID devices do not need a physical electrical contact to transfer data • An RFID system has a transponder and a reader • The reader or interrogator may be able to read data or to read and write data but it is always called a reader

14. Touch-sensitive screen • Is a type of visual display unit that allows a user to interact with a application • The screen has been specially adapted so that the region just in front of the screen is criss-crossed by horizontal and vertical beams of infrared light • Breaking of these beams is detected at the receiving end of each beam by a series of photoelectric sensors • An electronic circuit connected to these sensors correlates broken horizontal and vertical beams and tells the computer the coordinates. • The executing application then maps the coordinates to an action

15. Graphics tablet • Allows graphics to be drawn into a computer by hand like drawing with a pencil and paper • Pressing the tip of the stylus against the surface operates a micro switch, which causes the movement to be recorded by computer • These commands ,may be operating system commands or application commands such as drawing commands in a drawing package • The board contains electronics to detect the position of the stylus tip

16. Voice Recognition • A computer can be trained to recognise a persons voice • The computer can do this be using a microphone, sound card and appropriate software • All of the components and software can turn speech into text • This system can be used to issue commands to the computer and to dictate sentences directly into applications

17. Digital Still Camera • This is an electronic device used to capture and store photographs digitally on a memory card • Most compact digital cameras are multifunctional (Can record sound and video as well as photographs) • All use either a charge-coupled device(CCD) or a CMOS image sensor to sense the light intensities across the focal plane