Chapter 5 - Input devices Flashcards Preview

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Flashcards in Chapter 5 - Input devices Deck (46)
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What do 2D scanners do?

they convert hard-copy documents into an electronic form
these can be stored in a computer memory


How do 2D scanners work?

A scan head moves across the document producing an image
this is sent to a lens via a series of mirrors
the focused image falls on a charge-coupled device (CCD) which consists of a number of integrated circuits
the original document is turned into a format that can be stored in a computer's memory


What are applications of 2D scanners?

at airports to read passports


What do 3D scanners do?

scan solid objects and produce an electronic 3D image


How do 3D scanners work?

They use lasers/x-rays


What are CT 3D scanners used for?

to produce a 3D image of a solid object


How does tomography technology work?

splits up the object into a number of thin slices
use x-rays, radio waves or gamma imaging methods
the resultant image allows a solid object to be stored as a series of digital values representing each slice


What do barcodes consist of?

a series of light and dark lines of varying thickness (representing each digit or character)


Where are barcodes used?



What are the advantages of barcodes for managers?

easier and faster to alter prices
give instantaneous and comprehensive sales trends
no need to price each item
allows automatic stock control
can check customer's buying habits more easily


What are the advantages of barcodes for customers?

faster checkouts
less chance of errors
get an itemised bill
cost savings can be passed on to the customer
better tracking of sell-by dates


What are QR codes?

a type of barcode
hold considerably more data than barcodes


How are QR codes read?

by built-in cameras in smartphones or tablets
sends information back to the phone or tablet


What do the microprocessors in digital cameras do?

adjusts shutter speed
operates the flash
adjusts the aperture
removes red eye
reduces handshake


How are images captured on a digital camera?

light passes through the lens onto light-sensitive cells - made up of thousands of tiny elements called pixels
the number of pixels determines the size of the file needed to store the image


How do keyboards work?

keys are pressed by the operator to enter data directly into the computer
when a key is pressed it completes a circuit and a signal is sent to the microprocessor which interprets which key has been pressed


Why do most computer systems use a keyboard buffer?

entering data by a keyboard is a slow process
prevents the microprocessor from waiting for keys to be pressed


What are the health risks posed by typing?

RSI - repetitive strain injury


What are the most common pointing devices?

mouse and the trackerball


What do pointing devices control on screen?

a cursor to select options from menus


Which out of a mouse and a trackerball poses less health issues?

trackerball (do not get RSI as you don't have to repeatedly click a mouse button)


What are microphones used for?

to input sound into a computer


How does a microphone work?

when picking up a sound:
a diaphragm vibrates producing an electric signal
a sound card in the computer converts the signal into digital values which can be stored in its memory


How does speech recognition use microphones?

speech recognition:
works by converting speech patterns into a digital form (broken into phonemes which are compared to words in a built-in dictionary), spoken word then recognised


How does voice recognition use microphones?

voice recognition:
used to identify if a 'known' person is speaking (such as in a security system), the software compares the wave patterns from the voice with wave patterns stored in memory


What do touchscreens do?

allow selections to be made by simply touching an icon or menu option on a screen


What are the 3 main types of touchscreens?

capacitive, infra-red, resistive


How do capacitive touchscreens work?

uses layers of glass that acts as a capacitor
when the top layer is touched, the electric current changes
microprocessor works out the coordinates of where the screen was touched


What are the benefits of capacitive touchscreens?

medium-cost technology
good visibility in strong sunlight
allows multi-touch capability
very durable


What are the drawbacks of capacitive touchscreens?

can only use bare fingers/conductive stylus