Input and Output Devices Flashcards
Describe how a barcode scanner works (5)
red laser shone on barcode
light reflected back (white lines reflect more light)
sensors detect light
microprocessor decodes data
bars will give different binary values
Barcode applications (3)
supermarket checkout
library system
Airport check-ins
Disadvantages of keyboard (3)
dirt/food can get into keys
easy to make a mistake
can be slow
Advantages of concept keyboard (2)
fewer typing errors
stops dirt/food as it has protective layer
Touchscreen application (3/5)
Ticket/ information kiosk
Mobile phone/ tablet
Control room interface
How inkjet printer works (3)
print head moves nozzles side to side across page
nozzles spray liquid ink droplets on paper
ink droplets created using piezoelectric or thermal bubble technology
Benefits of laser printer (3)
can print duplex
Faster printing
Cheaper long term (does not have to purchase ink cartridges)
Advantages of inkjet printer (3)
Cheap to initially purchase
high quality output
relatively quiet
Inkjet disadvantages (3)
ink cartridges dont last long
expensive to run
printing can smudge
How laser printer works (4)
Uses toner cartridges
Uses charged print drum
Uses static electric charges
Toner fused to paper
Application of 3D printers(3)
prototypes/models
parts of vintage car
creating museum artifacts
When are inkjet printers used? (3)
high quality images
photographs
low volume printing
When are laser printers used? (2)
high speed printing
large volume printing
What are barcodes made up of?
series of black and white parallel lines
Appearance of QR code
matrix of black squares on white background
How do resistive touchscreens work (5)
uses multiple layers of material
transmits electric currents
when touched, top layer pushed into bottom layer
electric current changes
location of touch found
Advantages of resistive (2)
cheap technology
can use gloved fingers to input
Disadvantages of resistive (3)
does not allow multi-touch
poor visibility in sunlight
vulnerable to scratches
How do capacitive touchscreens work (4)
electric fields created between glass layers
sensors monitor electric field
touched = electrostatic charge transferred to finger
location of touch calculated
Advantages of capacitive touchscreen (3)
allows multi-touch
durable surface
good visibility in sunlight
Disadvantages of capacitive touchscreen (2)
cannot use when wearing gloves
screen will shatter on impact
How do infrared touchscreens work? (5)
infrared rays sent across screen from edges
rays form grid around screen
sensors capture beams
infrared ray broken by finger touching screen
calculation made where beam broken to locate touch
Advantage of infrared touchscreens (3)
allow multi-touch
allows gloved fingers to be used
durable
Laser printer disadvantages (3)
larger carbon footprint
more time to warm up
toner cartridge more expensive
Disadvantages of infrared touchscreens (3)
sensitive to moisture
sensitive to light interference
accidental activation if infrared disturbed
How QR code works (7)
scanned by camera
light reflected back
black squares reflect less than white squares
3 large squares define alignment
square’s data decoded - each square has binary value
processed by app
links to website or document
QR code benefits (3)
hold more data
easier to read - can be read just using cameras
easier to transmit QR codes
QR code disadvantages (2)
can be used to transmit malicious codes
more than one QR format available
Why might a capacitive touchscreen not work if the person is wearing gloves (2)
gloves are not conductive
gloves block charge from finger
How can a mobile phone be used without removing gloves
use capacitive gloves - allows charge to be disturbed
How can a barcode help manage stock (3)
identifies unique product
can automatic re-order product
can be used to look up product
How digital cameras work (5)
images converted from analogue to digital using ADC
image turned to pixels
each pixel given value/colour
pixels form grid
pixels stored in sequence
How DLP screen works (5)
uses tiny mirrors
mirrors laid out in grid
mirrors tilt towards/away from light source
mirrors reflect light towards lens
colour produced using colour wheel
Benefit of LCD projector (3)
uses less power
higher resolution
runs quiter
How optical mouse works (5)
shines LED under mouse
light reflects back through lens
converted to value
value transmitted to computer
computer determines direction and speed of movement
How keyboard works (4)
key pushes switch on circuit board
completes circuit
location of press calculated
location corresponds to ASCII value
When does an interrupt occur (3)
paper jam
out of ink
out of paper
What happens when paper gets jammed in printing process (2)
printing stops
interrupt is sent to computer
Examples of output devices (3)
monitor
speaker
headphones
Examples of input devices (3)
keyboard
mouse
microphone
What type of device is an actuator (output or input)
output device
LED benefits (3)
consumes less power
has bright screen/colours
lasts long
Actuator description
operated by signals to cause physical movement
How barcode finds price of product (3)
database stores data
barcode value transmitted to database
price is found
How LCD works (6)
beam of light generated by a bulb
light sent to group of chromatic-coated mirrors
mirrors reflect light back at different wavelengths corresponding to RGB
3 different light components pass through 3 LCD screens
images combined using prism to create full colour image
image passes through projector lens onto a screen
What does LCD stand for
Liquid Crystal Display
How 2D scanner works (5)
paper placed on a glass panel
light illuminates document
scan head moves across document
lens focuses on document image
scanned image turned to electric form by CCD
Applications of 2D scanners (3)
airports - read passport
OCR software - read text
digital camera
How 3D scanners work (3)
object has x,y coordinates
scans along coordinates
scanned image used by CAD
What do QR codes stand for
quick response codes
How microphone works (3)
diaphragm vibrates producing electric signal
signal goes to sound card
converted into digital values
