Input / Output devices

They use check digit for validation. If the check digit does not match the calculated value it gives a input error. The validation is embedded into the barcode reader There is also a code underneath in case barcode cannot be read so can be inputted manually

• Light illuminates the barcode • More light reflected from white areas than black bar • Reflected light is captured by photoelectric cells that generate a set of electrical pulses. That correspond to black or white stripes • Pulses then converted to binary

Universal product code version ‘A’ (UPC-A) / European Article Number (EAN) - Used in retail and warehousing, uses letters and numbers Code 128 - Used in transport and shipment tracking, uses numeric digits

Uses long guard bar to show start and end. Alternates dark and light of varying thickness. Left side manufacturer number. Right side the product number. Check number on the right

Right hand code inverse of left-hand codes Left hand have odd number of black bars Right hand have even

When captures an image, it breaks it up through the lens into a grid of pixels They sense the colour by using RGB filters.

• Negative charge is applied to the drum. • A laser beam is directed at the drum. • Laser beam is directed using a mirror • Negative charge is neutralised where laser strikers • Negative charge is applied to the toner • Toner sticks to neutralised areas of drum • Positively charged transfer roller assists transfer of toner from drum to paper • Heat fuses toner onto the paper

Allows data to be transmitted wirelessly using radio waves. Uses a transponder and a reader.

Passive: Do not contain power supply. Powered by radio energy transmitted by the reader. Antenna collects energy from transmitter to activate chip. Range is 1m, some systems require being really close to tag Active: Small battery in tag, device transmit identifier at regular intervals. Depending on power supply range can be up to 200m.

Using radio signals means system does not require line of sight from tag and reader Readers can process multiple tags at a time as each have their own unique identifier

• Reader transmit encoded radio signal to interrogate the tag • Tag receives message and responds with identifier and any other stored data • Reader communicates with database to store and evaluate data

• Capture light with array of photosensors • Amount of light represents analogue voltages • Analogue voltage converted to digital values using a ADC • Digital values used to create pixel data • Pixel data then represents the colour creating the image