Input-Output Devices Flashcards
How do Barcode Readers work?
Uses a check digit for validation
Calculates the digit and compares it to the end of the code.
Usually done through the barcode, but can be done manually.
A light illuminates the code, more is reflected in the white areas than the black ones.
Captured by Photoelectric cells that generate electrical pulses corresponding to the stripes.
Which are processed and converted to a binary number.
Often then indicates a successful read.
How do Digital Cameras work?
Similar to a scanner.
Picks up an image and breaks it down.
This is into a grid of pixels, based on light intensity and stored in the cameras memory.
These are given an RBG value for colours.
How do Laser Printers work?
A laser printer uses a laser beam to heat up and melt toner particles.
The laser beam is directed at a rotating drum coated in a photoconductive material.
This becomes positively charged in areas where the laser hits it.
The negatively charged toner particles are then attracted to the positively charged areas on the drum.
The drum then transfers the toner particles onto paper.
Which is then heated causing the toner particles to melt and fuse onto the paper.
This creates a permanent image.
What is RFID?
Data that is transmitted wirelessly over radio waves with a transponder and a reader.
Uses tags with unique identifiers which store data.
Some in a non-volatile memory cell and some in a volatile form.
What are Passive Devices?
Devices that don’t use a power supply, instead powered with radio energy transmitted by the reader.
The antenna collects this energy and activates the chip, with a range of up to a metre.
How do Active Systems work?
They use a small battery, transmitting its identifier at regular intervals.
This has up to 200m range and commonplace in shops with battery powered tags.
How do Active Systems work in use?
The reader transmits an encoded system to check with the tag.
This receives the message and responds with its identifier and any other stored data.
The reader then stores this and evaluates it in a database
