Section 1 - Chapter 4: Input Devices Flashcards
What are barcodes?
Used for identification in thousands of applications.
There are two types of barcodes:
- Linear barcodes
- 2D barcodes such as quick response (QR) code
Why are 2D codes used?
To provide the user with further information such as a map of their location, product details or a website URL.
What are the 4 types of barcode readers?
- Pen-type readers
- Laser Scanners
- CCD readers
- Camera based readers
How does a pen-type reader work?
A light source and a photo diode are placed next to each other in the tip of a pen. To read a barcode, the tip of the pen is dragged across all the bars at an even speed. The photo diode measures the intensity of the light reflected back from the light source and generates a waveform that is used to measure the widths of the bars and spaces in the barcode.
Advantages of pen-type reader
- Most Durable
- Portable
Disadvantages of pen-type reader
Applications are limited because they must come into direct contact with a barcode to read it
What are Laser Scanners?
Laser scanners work in the same way as pen scanners except they use a laser beam as the light source.
What are camera-based readers?
A camera-based imaging scanner uses a camera and image processing techniques to decode a 1D or 2D barcode.
Applications of camera-based readers
- Age verification
- Couponing
- Event ticketing
What are digital cameras/CCD/CMOS?
A digital camera uses a CCD or CMOS (Complementary Metal Oxide Semiconductor) sensor comprising millions of tiny light sensors arranged in a grid. The binary data from each sensor is recorded onto the camera’s memory card so that the image can be reproduced using suitable software at a computer
A CCD sensor tends to produce higher quality images and they are used in higher end cameras. They are also more reliable since the technology has been around for much longer. This however, is at the cost of power consumption, using up to 100 times that of a CMOS sensor
What are Radio Frequency Identification (RFID)?
This technology uses both input and output - an input device to read the signal from an RFID chip, and output to transmit a signal from an active tag.
What is the difference between a barcode reader and an RFID?
An RFID tag can be read without the line of sight from up to 300metres away. They can also pass stored data from the tag to the receiver and vice versa.
What are active tags?
Active tags are physically larger as they include a battery to power the tag so that it actively transmits a signal for a reader to pick up. These are used to track things likely to be read from further away.
What are passive tags?
Passive tags are much cheaper to produce as they do not have a battery. They rely on the radio waves emitted from a reader up to a meter away to provide sufficient electromagnet power to the card using its coiled antenna. Once energised, the transponder inside the RFID tag can send its data to the reader nearby.
