External Hardware Devices Flashcards
What is a Barcode reader?
A bar code represents a code number for a product and is a set of
vertical lines of different thicknesses that represent a number.
What do the lines of a barcode tell us?
- Country of manufacture
- Name of manufacturer
- Product code
How does a barcode reader work?
Barcode readers or scanners are used to input data from bar codes:
* It scans or ‘reads’ the barcode by using a visible red light
* A light sensor measures the reflected light, where white areas of bar code reflect more light than black areas so creating an analogue waveform of the bar code
* The analogue waveform is converted into digital data that is interpreted by the computer to identify product data
* A check digit on the end of the bar code is used to ensure bar code validity
How are pictures from a digital camera stored?
Pictures taken using a digital camera are stored on a memory card and can be transferred to a computer by:
* Connecting the camera to the computer via a USB port or
* By plugging the camera memory card into the computer card reader
How does a digital camera operate?
Digital cameras operate as follows:
* When a picture is taken the image strikes the camera sensor
* The sensor records the amount of (RGB) light received and converts it into a digital value
* The image sensor records in RGB format so that all other colours can be created within the image
* The picture is then stored as an image file on a memory card inside the camera where the image file contains a series of digital data for each pixel in the picture
* Image files can be stored in RAW uncompressed format that contains all the original image detail, or in compressed format such as JPG or TIFF
How can imaging software be used?
Image editing software can be used to modify images that have been imported
from the digital camera into the computer; typical improvements include:
* Red eye removal
* Cropping or removing unwanted parts of the image
* Modifying the brightness/contrast
* Changing the image resolution
How do laser printers work?
Laser printers are used in many workplaces and function as follows:
* They operate on a page at a time and files that require printing are sent to the laser printer using a page description language
* The printer processes this file and creates a bitmap pattern
for the page
* The printer laser beam scans along and across the drum inside the printer creating the same pattern as the page that requires printing; this builds up a pattern of static electricity which attracts toner (powdered ink) onto the page
* The toner is then fused onto paper by heat and pressure, using a similar method to a photocopier
What is the main advantage of laser printers?
The main advantages of laser printers are their print speed; commercial printers can operate at hundreds of pages per minute and also there is high-quality dry page output.
What are Radio frequency identification tags (RFID)?
Radio frequency identification tags (RFID), are fixed to products and the tag will be programmed with information, similar to a barcode.
How do Radio frequency identification tags (RFID) operate?
The RFID reader operates as follows:
* RFID tags have an antenna (normally a flat spiral aerial) that is used to communicate with an RFID reader for tracking purposes
* The RFID reader transmits a radio signal which is received by the RFID tag and a programmed information code is returned to the reader
* This code is then decoded and translated into digital data that is interpreted by the computer to identify the information received.
What are the advantages of Radio frequency identification tags (RFID)?
- RFID tags do not need a power source as the signal from the ‘reader’ energises the passive tag and causes it to transmit its ID code.
-RFID tags can be used for security purposes in stores to prevent theft as an item that is not paid for will set off an alarm when it is removed from the store
What are the disadvantages of Radio frequency identification tags (RFID)?
The RFID range is reduced where the tag does not have its own power source.
