external hardware devices

• What is a barcode reader

  A device that uses lasers to read the black and white lines of a barcode
• What is the purpose of a barcode reader

  to translate barcodes into numbers which then be translated by a computer
• How suitable is a barcode reader for its purpose

  It is faster to use a barcode scanner than to hand-type a series of numbers
• How does a barcode reader work (4)

  • Light from a laser is directed at a barcode and a sensor detects the intensity of the light that bounces back
  • black bar absorbs more light -> less light reflected -> translated to a binary reading of 1
  • white bar absorbs less light -> more light reflected -> translated to a binary reading of 0
  • Pattern of 1s and 0s creates a unique identity
• What is a digital camera

  A device for creating digital images of photographs
• What is the purpose of a digital camera

  To capture and store photos in a digital format
• How does a digital camera work (5)

  • Light is let in through shutter and focused by the lens
  • Light is directed through RGB filters and then focused onto CCD sensor
  • Intensity of light is measures by millions of tiny sensors arranged in a grid on the CCD sensor
  • Light levels for each pixel are recorded as binary
  • this information is stored as an image in the cameras memory
• What is a laser printer

  A device that uses lasers and toner to create mono and colour prints
• What is the purpose of a laser printer

  To produce high quality paper copies of images
• How does a laser printer work (5)

  • Rotating drum is given a -ve static charge
  • Laser beam shines a reverse image of the page at the drum by discharging certain parts of the drum
  • A laser light reverses the charge of the rotating drum so that it is +vely charged
  • -vely charged toner sticks to the areas of the rotating drum that are +vely charged
  • toner is transferred from drum to paper and fused using a heat roller
• What is RFID


  'radio frequency identification'

  A microscopic device that stores data and transmits is using radio waves
• What are the various purposes of RFID

  wireless tracking device, consumer contactless payments
• How does RFID work(3)

  • Powered receiver emits radio frequency energy
  • Transponder antenna (sends and receives signals) becomes energised by radio waves
  • transponder can then send data to receiver
• What is a passive RFID tag (2)

  • No power source themselves, rely on radio waves from receiver for energy
  • tansponder needs to be placed very closely to receiver
• What is an active RFID tag (2)

  • Have their own power source
  • Can broadcast its own signal to receivers upto 300m away