Chapter 4 - Input devices

• 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

• 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

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

• 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

• 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

• 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)

• 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