input devices Flashcards
how do 2D scanner work
1- paper is placed on a glass panel
2- bright light illuminates the document
3- scan head moves across the document
4- lens focuses on the document image
5- scanned image is turned into electrical form by the CCD (made up of thousands of light-sensitive pixels and each pixel creates electric charge when light falls on it)
where are 2D scanners used
at airports to read passports
OCR software used to read text
what do 3D scanners do
they scan solid objects and produce 3D image
how do 3D scanners work
they take images at several points along x,y,z coordinates
where are 3D scanners used
X-rays, MRI scanners
what are barcodes
a series of dark and light parallel lines. Numbers from 0 to 9 are represented in each line
how do barcode scanners work
1- red laser is shone at the barcode
2- light is reflected back (the dark areas reflect little or no light)
3- sensors detect the light back
4- pattern is converted to digital data
5- microprocessor interprets the data
6- each digit is made up of 2 dark and 2 light lines
what are advantages to the company of using barcode scanners
easy to change price of stock items
no need to price every item on shelf
allows automatic stock control
what are advantages to the customer of using barcode scanners
faster checkout
reduces errors
itemized bills
how do QR (quick response) codes work
1- QR code is scanned by the camera
2- light is reflected back (black squares reflect less than white squares)
3- the squares’ data is decoded (each square has a binary value)
4- this is processed by an app
5- this will link to a website or a link
what are some advantages of QR code against barcode
QR code can contain more data
QR code can be read from any angle
QR code is faster to scan than barcodes
how do keyboards work
keys are pressed by the operator to enter data directly to the computer
when the key is pressed, it completes a circuit and a signal is sent to the microprocessor which interpets the key that has been pressed
what are benefits of concept keyboards
fewer typing errors
speeds up time
requires less training
how do microphones work
when the microphone picks up a sound, the diaphragm vibrates and this produces an electrical signal. A sound card in the computer converts the signal into digital values which can be stored in its memory.
how do voice recognition work
1- users voice is converted into digital signal
2- spoken words produce a digital pattern
3- software compares these patterns to the patterns that are stored in memory
4- if they match, the person is identified
how do speech recognition work
converts speech patterns into digital form
what are some problems of speech recognition
the software needs to be trained, some dialects and accents can cause a problem
what are applications of speech recognition
siri, smart cars
what are three different types of touchscreens
resistive, capacitive, infra-red
how do resistive touchscreens work
1- they use multiple layers of material that transmits electric current
2- when top layer touches lower layer, the current changes and the location of where the screen was pressed is found
advantages of resistive touchscreens
cheap to make
can be used when wearing a glove
disadvantages of resistive touchscreens
poor in sunlight
easily scratched
doesn’t allow multi-touch
how do capacitive touchscreens work
they have conductive layers
when the top layer is touched, the electric current changes
microprocessor works out the coordinates where the screen was touched
advantages of capacitive touchscreens
good visibility in sunlight
very durable
allows multi-touch
disadvantages of capacitive touchscreens
can only use bare fingers or a conductive stylus
how do infrared touchscreens work
it detects heat or uses infra-red sensors to detect touch
microprocessor works out where the screen was touched
advantages of infrared touchscreens
can use bare hands, gloved hands or a stylus
good screen durability
allows multi-touch
disadvantages of infrared touchscreens
relatively expensive
heat-sensitive systems only allow bare hands to be used
how do sensors work
they send data to the real world from a computer
they often require an analogue to digital converter
monitoring applications of sensors
burglar alarm, street lights
control applications of sensors
traffic light control, greenhouse environment
what do interactive whiteboards do
they allow computer images to be displayed by a digital projector, they allow users to write on the whiteboard and stores it into computer memory
