Chapter 5 - Input devices Flashcards
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
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
How do infra-red touchscreens work?
uses glass and can either detect heat or uses infra-red sensors to detect touch
microprocessor works out where the screen was touched based on sensor/heat data
What are the benefits of infra-red touchscreens?
allows multi-touch capability
can use bare fingers, gloved hand or stylus
good screen durability
What are the drawbacks of infra-red touchscreens?
relatively expensive technology
heat-sensetice systems only allow bare fingers to be used
How do resistive screens work?
uses an upper layer of polyester and bottom layer of glass
when the top layer is touched, it completes a circuit
microprocessor works out the coordinates of where the screen was touched
What are the benefits of resistive screens?
relatively inexpensive technology
can use bare fingers, gloved hand or stylus
What are the drawbacks of resistive screens?
poor visability in stong sunlight
doesn’t allow multi-touch capability
screen vulnerable to scratches
What do sensors do?
send data from the real world to a computer
What type of convertors do you need for sensors to convert real world data into data which the computer can understand
anaolouge to digital converter (ADC)
What type of systems do sensors form a part of?
monitoring or control systems
What does monitoring mean?
reports the status of a system via a computer/microprocessor
What does control involve?
altering devices so that the output affects the next input to the computer
What are the different types of sensors?
temperature moisture/humidity light infra-red motion pressure acoustic/sound gas pH magnetic field
What are examples of monitoring systems?
montioring a patients vitals in hospital
burgular/intruder alarm systems
monitoring pollution levels in the air
checking key data in a car engine
What are examples of control systems?
traffic light control greenhouse environment street lighting anti-lock braking system control of a chemcial/nuclear process
What are interactive whiteboards?
allows computer images to be displayed using a digital projector
allow users to write on the whiteboard and the text/images created to be stored in computer memory
What is an input device?
hardware that allows a computer to receive data from the outside world
