3.7.4.1 Input and Output Devices.

Question 1

What is a barcode?

Answer 1

Printed diagrams that consist of light and dark portions.

Question 2

Name the two types of barcodes.

Answer 2

1D and 2D.

Question 3

Give an advantage of a 2D Barcode.

Answer 3

Can contain more information in the same amount of space as a 1D barcode.

Question 4

Give a disadvantage of a 2D barcode.

Answer 4

They require more processing in order for the information to be extracted.

Question 5

Name the parts of a barcode reader.

Answer 5

Laser light source.
Lens.
Photodiodes.
Mirror.

Question 6

What role does the mirror play in a barcode.

Answer 6

Reflects light from the laser onto a printed barcode. The light reflected passes through the lens and is incident on the photodiode.

Question 7

What role does the photodiode play in a barcode.

Answer 7

Turns the light into an electrical charge.

Question 8

What happens once the light is converted into an electrical charge (barcode).

Answer 8

The electrical charge can be measured and processed to form a digital signal representing the contents of a barcode.

Question 9

What is the purpose of the light and dark portions on a barcode?

Answer 9

Light portions reflect most of the light whereas dark sections absorb incident light.

Question 10

What do the light and dark portions in a barcode correspond to?

Answer 10

Binary: 1,0.

Question 11

What error detection and prevention methods does a barcode have?

Answer 11

Parity bits and check digits built in, allowing computers to tell whether a barcode has been read correctly.

Question 12

What happens if a barcode fails to scan correctly?

Answer 12

Possibly due to dirt on the barcode, the reader will continue to scan until the barcode is read successfully.

Question 13

How many time can a barcode read a barcode in a second.

Answer 13

1000s of times per second.

Question 14

What do digital cameras consist of?

Answer 14

A lens that focuses light on a sensor.

Question 15

What regulates the path of light (dc).

Answer 15

The path of light

between the lens and the sensor is regulated by a shutter.

Question 16

What are the two sensors commonly used in digital cameras?

Answer 16

CMOS (Complementary metal oxide semiconductor).

CDD (Charge coupled device).

Question 17

What do both sensors do (DC).

Answer 17

Convert incident light into electrical charge.

Question 18

What represents a pixel in the image? (DC).

Answer 18

Charge builds up in cells, each of which represents a pixel in the image.

Question 19

What happens once the photograph has been taken?

Answer 19

The charge in each cell is measured and converted to a digital value which is then processed by the camera and stored as a digital image.

Question 20

How many cells are for each pixel in a colour camera.

Answer 20

Multiple, each of which has a filter that only allows in certain wavelengths of light.

Question 21

What do the certain wavelength of lights allow for?

Answer 21

The camera to build up a separate image for the intensity of each colour of light which can then be combined to form a full colour photograph.

Question 22

What is a Bayer filter?

Answer 22

A special colour filter used in digital cameras that

has the same number of green filters as red and blue combined.

Question 23

What is an advantage of a Bayer filter?

Answer 23

Produces an image that is a closer approximation of what the human eye, which is most sensitive to green light, sees

Question 24

What is a laser printer?

Answer 24

An output device that produces images on paper from digital signals.

Question 25

What do laser printers consist of?

Answer 25

Laser printers, which print whole pages at a time, consist of:

Laser light source.
A mirror.
A drum.
A toner roller. 
A fuser.

Question 26

What happens when a document is printed?

Answer 26

The drum is positively charged all over before the laser is directed at its surface by the mirror.

Question 27

What happens to the areas on which the laser is incident?

Answer 27

They are discharged, leaving behind an impression of the page in electrical charge on the drum.

Question 28

What charged toner does the toner roller dispense onto the drum?

Answer 28

The toner roller dispenses negatively charged toner (a type of plastic powder) onto the drum.

Question 29

What is the toner attracted to?

Answer 29

As opposite charges attract, toner is attracted to the positively charged portions of the drum.

Question 30

What is then done with the toner?

Answer 30

The toner is then applied to the paper by the drum before the paper is heated by
fusers, fixing the toner to the paper.

Question 31

What differs from this process when working with a coloured printer?

Answer 31

Colour printers apply the same process except with four different colours of toner: cyan, yellow,
magenta and black (CYMK) to achieve full colour prints

Question 32

Define an RFID.

Answer 32

Radio frequency identification.

Method of transferring information wirelessly between a tag and a reader.

Question 33

Give examples of when RFID is used.

Answer 33

Contactless credit and debit cards.

In some hotel room cards.

Question 34

Outline the role of the chip in the RFID tag.

Answer 34

To contain a small amount of memory. The chip is attached to a coil of
wire which acts as an antenna.

Question 35

What is meant when we say an RFID tag is passive?

Answer 35

They induce enough power wirelessly from the reader to operate the chip.

Question 36

What is meant when we say an RFID tag is active?

Answer 36

Contain a small power supply like a batter.

Can be used much farther away from readers than passive, which must be held within a few centimetres of their reader.

Question 37

What is stage one of scanning a barcode?

Answer 37

When an RFID tag is scanned, the reader emits radio waves which are picked up by the
tag’s antenna.

Question 38

What is stage two of scanning a barcode?

Answer 38

The power induced in the tag’s antenna from these waves is enough to power the chip

Question 39

What is stage three of scanning a barcode?

Answer 39

The chip then uses its antenna to emit its own radio wave

Question 40

What is stage four of scanning a barcode?

Answer 40

The radio wave contains the information held on the chip. This wave is picked up by the reader which decodes the information and returns the information to a computer.