Chapter 4 - Input devices

Question 1

Barcodes

Answer 1

• used for tracking parcels, blood, tissue and organ products, etc
• linear barcodes and 2D barcodes
• QR codes are used for ticketless entry to concerts, linked to more information or a website

Question 2

Barcode readers - pen-type readers

Answer 2

• Photo diode measures intensity of light reflect back from light source and generates a wave form that is used to measure the widths of the bars and spaces in a barcode
• +ve: Most durable type of barcode reader – can be tightly sealed against dust, dirt, etc.
• -ve: must come in direct contact with barcode to read
• Use – with laptops or very low volume scanning applications

Question 3

Barcode readers - laser scanners

Answer 3

• Use laser beam as light source instead
• +ve: reliable, economical for low-volume applications
• Use – in-counter units in supermarkets

Question 4

Barcode reader - camera-based readers

Answer 4

• Uses camera and image processing techniques to decode a 1D/2D barcode
• +ve: can read barcodes on any surface (printed, onscreen) that are also damaged, poorly printed
• Use – age verification, couponing, event ticketing
• Can scan QR codes that are linked to websites, information

Question 5

Radio frequency identification (RFID)

Answer 5

• used in the same way as barcodes for identifying and tracking goods and cars to bank cards and animals
• can be read without line of sight and from upto 300m away
• consists of microchip transponder (a device for receiving a radio signal and automatically transmitting a different signal) and antenna

Question 6

Passive and active tags

Answer 6

• active tags - include battery to power the tag to actively transmit a signal for a reader to pick up e.g. cars on motorway, runners in marathon
• passive tags - don’t have battery, rely on radio waves from receiver to power chip to send data to reader 1m away e.g. groceries, smart cards (Oyster card, contactless bank card)

Question 7

Digital cameras

Answer 7

• binary data from light sensors arranged in a grid are recorded onto camera’s memory card
• CCD (charge-coupled device) sensors produce better quality images and are more reliable than CMOS (complementary metal oxide semiconductor) sensors, but consume more power
• Mastercard allows usage of selfies instead of passwords that can be guessed or forgotten; 3D face recognition compares proportions of features to stored code