3.7.4.1 - input and output devices

Question 1

4 input output devices

Answer 1

Barcode reader
Digital camera
Laser printer
RFID(Radio frequency identification)

Question 2

What are barcodes?

Answer 2

A means of representing data in machine readable form. Consist of a series of parallel black and white lines with varying widths which represents characters.

The last character is typically a check digit(computer applies algorithm to this digit as an error checking method to make sure no errors occurred in input)

Question 3

How does barcode reader work

Answer 3

A laser is passed over the barcode

there is varying intensity of light reflected back, which is detected by some sort of light sensor(photo diode or CCD sensor)

this generates a current which can make an analogue wave form

an ADC is used to convert the analogue waveform

this digital waveform can be interpreted as binary by software to produce a result of characters

Question 4

what are guard bars

Answer 4

long narrow pairs of bars in the middle and end of the barcode to be used as referrnce points by the scanner

Question 5

What is a laser printer and how does it work

Answer 5

• a rotating drum is covered in a chemical which has an electric charge
• a laser is reflected by moving mirror onto the drum, where the laser hits the drum becomes discharged
  this creates the image on the drum
• as the drum rotates it picks up toner which is attracted to charged parts
• the paper is given an opposite charge to the toner so when it is passed under the toner sticks on to the paper
• the paper is heat treated to fuse the toner onto ith

Question 6

How does laser printing vary between colour amd mono printing

Answer 6

4 toners are used for the 4 printing colours to produce a full range of RGB - magenta, cyan, black , yellow

Question 7

How does RFID(Radio Freqeuncy Identification) system work?

Answer 7

• System consists of tag and reader
• a small tag consists of an antenna to recieve and transmit data and a chip to process the signals
• The chip contains information such as a unqiue identifier and other relevant infromation and a modem to modulate and demodulatte information
• signals are used to transfer information back and forth or to track the physical location

Question 8

What are the two types of RFID?

Answer 8

active : tag contains a power source which can extend the range of to 100 metres
passive: powered by the radio wave energy from the reader, range up to 1 metre

Question 9

Uses of RFID

Answer 9

by farms ansd pet owners to track animals
to track vulnerable people
to secuirty tag items instores
foer contactless payments

Question 10

Digital camera

Answer 10

A shutter opens to let light into a lens
- the lens focuses light onto a sensor, made of CCDs or CMOSs
- the light hitting the sensors is converted to electrons and the charge is recorded for each pixel
- a colour camera uses 3 filters or 3 sensors for each pixel(RGB)
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