4.7.4.1 Input and Output devices

Question 1

Barcodes

Answer 1

Printed diagrams that consist of light and dark portions They contain information which can be read by a computer using a barcode reader.

Question 2

2D barcodes

Answer 2

Contain more information in same amount of space as 1D barcode, but requires more processing for information to be extracted

Question 3

Barcode reader

Answer 3

Mirror directs light from the laser onto the printed barcode.
Light reflected from the barcode passes through the lens and is incident on the photodiode which turns light into electrical charge.
Electrical charge can be measured and processed to form a digital signal representing the contents of the barcode

Question 4

Light & dark portions of barcode

Answer 4

Light portions reflect the most light
Dark portions absorb the most light
The pattern of light and dark stripes in the barcode correspond to binary 1 & 0s

Question 5

Barcode error detection

Answer 5

If it fails to scan correctly, the barcode continues to scan until the barcode is read correctly.
Barcodes scan 1000s of times per second which is hardly perceptible to humans

Question 6

Digital Camera

Answer 6

Consists of a lens that focuses light onto a sensor, the path of light between the lens are regulated by a shutter

Question 7

Digital camera sensors

Answer 7

Two sensors CMOS (complementary metal oxide semiconductor) & CCD (Charged couplet device) that convert incident light into electrical charge.

Question 8

Digital Camera Process

Answer 8

Charge builds up in the cells, each represent a pixel in the image
Once photograph is taken the charge of each cell is measured and converted to digital value processed by the camera and stored as a digital image

Question 9

Camera filters

Answer 9

Colour cameras have multiple cells for each pixel that each have a filter that only allows certain wavelengths of light.
The camera builds up a separate image for the intensity of each colour of light combined together to form a full photograph

Question 10

Bayer filter

Answer 10

Special colour filter used in digital cameras that have the same number of green filters as red and blue combined. It produces an image that is a closer approximation of the human eye most sensitive to green light

Question 11

Laser printer

Answer 11

The drum is positively charged all over, the laser is directed at the surface by the mirror. Incident areas by the laser are discharged leaving an impression on the page in electrical charge on the drum. Toner dispenses negatively charged toner onto the drum. Opposites attract toner attracted to positively charged portions of the drum. Toner applied to the paper by drum before the paper is heated by the fusers fixing the toner to the paper

Colour printers use cyan, yellow, magenta and black to achieve full colour prints

Question 12

Radio frequency identification

Answer 12

Method for transmitting information wirelessly between a tag and a reader. Used in contactless credit and debit cards and hotel room cards.
There is a chip inside the tag containing small amounts of memory. Chip attached to a coil of a wire acting as an antenna.

Question 13

RFID process

Answer 13

When scanned the reader emits radio waves which are picked up by the tags antenna. The power induced in the tags antenna from the waves is enough to power the chip, then uses the antenna to emit

Question 14

Active tags

Answer 14

Contains a small power supply like a battery

Question 15

Active tags

Answer 15

Contains a small power supply like a battery. Can be used further away from readers than passive tags which must be held within a few centimetres of their