Chapter 5 - Input devices
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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?
supermarkets
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 focuses 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