4. Input Devices

Question 1

What are the 2 types of bar codes?

Answer 1

1. Linear

2. 2D (QR codes)

Question 2

Name 3 examples of when QR codes are used?

Answer 2

1. Ticket-less entry to concerts
2. Access through gates to board plane
3. For mobile phones to get info

Question 3

Name the 4 types of bar code readers

Answer 3

1. Pen-type readers
2. Laser scanners
3. CCD readers
4. Camera-based readers

Question 4

Describe how a pen-type reader works

Answer 4

1. A light source and a photo diode are placed next to each other in the pen tip
2. Pen tip is dragged across all bars at even speed to read bar code
3. Photo diode measures intensity of light reflected back from light source
4. Generates wave form that is used to measure widths of bars and spaces in bar code

Question 5

What are the advantages of pen-type readers?

Answer 5

1. Most durable bar code scanner due to simple design
2. Can be tightly sealed against dirt, dust and other environmental hazards
3. Very portable

Question 6

What is the disadvantage of pen-type readers?

Answer 6

Limited application because they need to be in direct contact with the bar code

Question 7

Describe how a laser scanner works

Answer 7

The same way as a pen-type reader except they use a laser beam as the light source

Question 8

Where are laser scanners typically used?

Answer 8

In-counter units in supermarkets

Question 9

What are the advantages of laser scanners?

Answer 9

1. Reliable

2. Economical for low-volume applications

Question 10

How does a camera-based reader work?

Answer 10

Uses a camera and image processing techniques to decode a 1D or 2D bar code

Question 11

What are the advantages of a camera-based reader?

Answer 11

1. Can read bar code on any surface, printed or onscreen

2. Can read a bar code that is poorly printed or damaged

Question 12

What 2 sensors can be used in digital cameras?

Answer 12

1. CCD (Charged Couple Device

2. CMOS (Complementary Metal Oxide Semiconductor)

Question 13

What do the sensors do?

Answer 13

1. Comprises millions of tiny light sensors arranged in a grid
2. Binary data from each sensor is recorded onto camera’s memory cards so the image can be reproduced using suitable software on a computer

Question 14

Which of the 2 sensors produces the higher quality images?

Answer 14

CCD

Question 15

Which of the 2 sensors is more reliable?

Answer 15

CCD

Question 16

Which of the 2 sensors consumes less power?

Answer 16

CMOS - 100 times less than that of CCD

Question 17

What are RFID (Radio Frequency Identification) tags used for?

Answer 17

Identifying and tracking everything

Question 18

What are the input and output devices in RFID responsible for?

Answer 18

Input = reading signal from RFID chip
Output = transmit signal from active tag

Question 19

What are the differences between RFID technology and bar codes?

Answer 19

1. An RFID tag can be read from up to 300m away and without line of sight
2. RFID can pass stored data from tag to receiver and vice versa

Question 20

What does an RFID chip consist of?

Answer 20

1. Small microchip transponder

2. An antenna (larger than chip)

Question 21

Name an example of where RFID chips are used?

Answer 21

Embedded into special capsules and injected under skin for identification of pets

Question 22

What is an active tag?

Answer 22

Physically larger as they include a battery to power the tag to actively transmit a signal for a reader to pick up

Question 23

What are active tags used for?

Answer 23

Tracking things likely to be far away (e.g. cars passing motorway toll booth or marathon runners passing mile markers)

Question 24

How does a passive tag work?

Answer 24

1. Rely on radio waves emitted from reader up to a metre away to provide sufficient EM power to card using its coiled antenna
2. Transponder inside RFID tag sends data to reader nearby once energised

Question 25

Are active or passive tags cheaper to produce?

Answer 25

Passive - no battery required

Question 26

What are passive tags used for?

Answer 26

1. Tagging items

2. Smart cards