Bar code

From GAWDAwiki

A bar code is a series of parallel black bars and white spaces, both of varying widths. Bars and spaces together are called elements. Different combinations of the bars and spaces represent different characters, such as numbers or letters. Each combination or sequence of bars and spaces is a code that can be translated into such information as price, product type, place of manufacture or origin of shipment. Related technologies include RFID, an alternative to the bar code.

How Bar Codes Work

Bar Code Readers

The bar code itself does not actually contain any detailed information. The pattern of alternating lines on a bar code represent a reference number, which is linked to information in a computer. A bar code reader is therefore required to read a bar code and interpret this number to access information. Bar code readers may be fixed, portable batch, or portable RF (radio frequency).

Fixed readers are attached to a host computer and terminal, and transmit one item at a time as the data is scanned.
Portable batch readers are battery powered and store data into memory for batch transfer into a host computer at a later time.
Portable RF readers can transmit data in real-time, on-line.

Bar Code Scanners and Decoders

The basic reader consists of a scanner and a decoder. Scanners capture the image of the bar code, and the decoder takes the digitized bar space patterns, decodes them, and transmits the decoded data to the computer.

There are several types of scanners:

Laser scanners use a single spot of light to sweep across the barcode in a linear fashion.
CCD scanners use an LED array with thousands of light detectors; the entire barcode image is captured and then transmitted.
Fixed position or automatic scanners are in a fixed position and read bar codes as they go by on a conveyor.
Handheld scanners, such as wands, are portable and may be carried from place to place, as in a warehouse.

When a scanner is passed over the bar code, the dark bars absorb the scanner's light while the light spaces reflect it. A photoelectric sensor receives the reflected light and converts it into an electrical signal. A low electrical signal is created for the reflected light and a high electrical signal is created for the dark bars. The width of the element determines the duration of the electrical signal. The decoder then decodes the signal into the characters represented by the barcode and passes it to a computer in traditional data format.

Types of Bar Code

There are different types of bar codes. Some bar codes are entirely numeric, whereas others have numeric and alphabetic characters. The type used is dependent upon the implementation, the data that needs to be encoded, and how the barcode is to be printed. There are several barcode standards, called "symbologies," each serving a different purpose. Each standard defines the printed symbol and how the scanner reads and decodes the printed symbol.

Types of bar codes include:

Uniform Product Code (UPC): the North American standard for several decades.
Automotive Industry Action Group (AIAG)
European Article Numbering System (EAN)
Reduced Space Symbology (RSS): an emerging standard for compressing bar codes so that they can fit into small spaces such as prescription bottles
Global Trade Item Number (GTIN): can read and store other types of code.^[1]