Input/Output Devices Flashcards
How does a Barcode reader interpret a barcode
- The Black bars will absorb more light so be less reflective - giving a reading of 1
- The while bars are more reflective so will give a reading of 0
- Patterns of 0s and 1s creates a unique identity
What are the principles of operation of a barcode reader
-A laser illuminates the barcode
-Reflected light is captured by photoelectric cells that generate a set of electrical pulses that correspond to the black and white stripes in the barcode
-These pulses are processed and converted into binary
What are the principles of operation of a digital camera
-The shutter opens to let light onto a CCD or CMOS sensor
-The intensity of light is measured by millions of sensors arranged in a grid on the sensor
-Light levels for each pixels are represented as binary
-This information is stored as an image in memory
What are the principles of operation of laser printing
-Data is sent to the printer driver
-Printer driver checks status and sends data to be stored in a printer buffer
-Printing process starts by giving a printer drum a negative charge
-As drum rotates, a mirror reflects a laser at the drum, removing negative charge in certain areas leaving the image in the Negative
-Printer release positively charged toner onto drum
-Feeder rolls negative paper through the printer which pulls positively charged toner off the drum
-electric charge removed from paper and goes through a fuser to bond ink
What are the principles of operation of an RFID chip
-Reader transmits an encoded radio signal to interrogate the tag
-Tag receives the message and responds with its identity and any other data
Name an advantage of using RFID
-Uses of radio signal means the system does not require a line of sight
-Readers can process multiple tags at the same time
Name an advantage of using RFID
-Uses of radio signal means the system does not require a line of sight
-Readers can process multiple tags at the same time
