4. Input Devices Flashcards
What are the 2 types of bar codes?
- Linear
2. 2D (QR codes)
Name 3 examples of when QR codes are used?
- Ticket-less entry to concerts
- Access through gates to board plane
- For mobile phones to get info
Name the 4 types of bar code readers
- Pen-type readers
- Laser scanners
- CCD readers
- Camera-based readers
Describe how a pen-type reader works
- A light source and a photo diode are placed next to each other in the pen tip
- Pen tip is dragged across all bars at even speed to read bar code
- Photo diode measures intensity of light reflected back from light source
- Generates wave form that is used to measure widths of bars and spaces in bar code
What are the advantages of pen-type readers?
- Most durable bar code scanner due to simple design
- Can be tightly sealed against dirt, dust and other environmental hazards
- Very portable
What is the disadvantage of pen-type readers?
Limited application because they need to be in direct contact with the bar code
Describe how a laser scanner works
The same way as a pen-type reader except they use a laser beam as the light source
Where are laser scanners typically used?
In-counter units in supermarkets
What are the advantages of laser scanners?
- Reliable
2. Economical for low-volume applications
How does a camera-based reader work?
Uses a camera and image processing techniques to decode a 1D or 2D bar code
What are the advantages of a camera-based reader?
- Can read bar code on any surface, printed or onscreen
2. Can read a bar code that is poorly printed or damaged
What 2 sensors can be used in digital cameras?
- CCD (Charged Couple Device
2. CMOS (Complementary Metal Oxide Semiconductor)
What do the sensors do?
- Comprises millions of tiny light sensors arranged in a grid
- Binary data from each sensor is recorded onto camera’s memory cards so the image can be reproduced using suitable software on a computer
Which of the 2 sensors produces the higher quality images?
CCD
Which of the 2 sensors is more reliable?
CCD
Which of the 2 sensors consumes less power?
CMOS - 100 times less than that of CCD
What are RFID (Radio Frequency Identification) tags used for?
Identifying and tracking everything
What are the input and output devices in RFID responsible for?
Input = reading signal from RFID chip Output = transmit signal from active tag
What are the differences between RFID technology and bar codes?
- An RFID tag can be read from up to 300m away and without line of sight
- RFID can pass stored data from tag to receiver and vice versa
What does an RFID chip consist of?
- Small microchip transponder
2. An antenna (larger than chip)
Name an example of where RFID chips are used?
Embedded into special capsules and injected under skin for identification of pets
What is an active tag?
Physically larger as they include a battery to power the tag to actively transmit a signal for a reader to pick up
What are active tags used for?
Tracking things likely to be far away (e.g. cars passing motorway toll booth or marathon runners passing mile markers)
How does a passive tag work?
- Rely on radio waves emitted from reader up to a metre away to provide sufficient EM power to card using its coiled antenna
- Transponder inside RFID tag sends data to reader nearby once energised
Are active or passive tags cheaper to produce?
Passive - no battery required
What are passive tags used for?
- Tagging items
2. Smart cards
