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Barcode Definitions and Symbologies
(excerpts from "Reading Between the Lines - Barcode Basics" by Datalogic)
What is a Barcode? Why Use Automatic Identification?
Modern automated warehouses, conveyor belts and manufacturing facilities increasingly require the implementation of identification systems.
One of the main requirements of the production process is the link between the information and the material flow. Thus, objects can be identified in real-time locations, which results in increased flexibility in every phase of the work process.
Optical identification represents approximately 75% of all identification systems currently in use. Thanks to bar codes, printed data can be easily and automatically read by means of a reading device. Bar code applications can be found in all fields of industry, retail, in the public sector and in everyday life. Moreover, a series of codes have been developed which can no longer be defined as bar codes, but as matrix codes, like the Data Matrix or MaxiCode. These two dimensional codes are used mainly in the logistics field.
The information encoded in a bar code can be optically read by means of a special device. It must be taken into account that surrounding conditions can considerably influence the reading and therefore the correct identification of the code. For example, if the information contained in a label is not correctly decoded, the item may be sent to the wrong location or even be destroyed. Barcodes can be found on moving objects, delivery notes, warehouse schedules, identifying plates, labels, etc. With respect to directly printing characters on objects by means of laser or ink-jet, labels have the advantage of being printed before being used. In this case, the place where the code is printed and used can be different, and this enables a low-cost and high-quality mass production in printing works.
Thanks to technological progress in opto-electronics, today data printed in a certain format can be automatically read and then downloaded to a computer by means of standardized interfaces. A bar code on a stationary object can be read by means of any hand-held reading device.
With a fixed-position laser scanner or a CCD-scanner, codes can be read at a remote distance on both moving and stationary objects.
How Optical Symbologies are Structured
Although a relatively recent technology, the world of barcodes is in continuous evolution. In the period between 1970 and 1980 all standard bar codes were developed, such as 2/5 Interleaved, Codabar, EAN/UPC, Code 39 and Code 128. At the same time, a number of special codes were created to meet the needs and demands of particular fields or applications. This is the case with Code 11, IBM Delta Distance, MSI-Code and many others. Only the best and most widely used bar code symbologies have survived and, in fact, since April 1993 the following bar codes have become the world-wide and European standard.
- EN 797 Barcode Symbology EAN/UPC
- EN 798 Barcode Symbology Codabar
- EN 799 Barcode Symbology Code 128
- EN 800 Barcode Symbology Code 39
- EN 801 Barcode Symbology Code 2/5 Interl.
The use of the 5 above-mentioned 1-D codes is further restricted. In trade, EAN has always been the standard, while in industry, especially in materials handling, logistics and warehouse management, Code 128 and EAN128 are increasingly used. Code 2/5 Interleaved, on the other hand, will in the long term be replaced by Code 128 as the latter allows the encoding of numerical data in an even more compact form by means of the character set C.
Code EAN 128 is defined by the EN 799 standard. Full details about codes are available at the National EAN organizations and their local associations.
- 1995: Development of the first stacked
codes, such as Code 49, Code 16K, Codablock and
The idea behind this kind of code is the connection between different codes related to each other. A checkdigit over the total set of codes guarantees the reliability of the data. 2D-Codes are based on the concept of the two-dimensional representation of information This means that the standard bar code could be defined as a 1D-code, as information is encoded only in the X-axis.
Stacked codes, on the other hand, include a second information level in the Y-axis. By condensing information in this way, i.e. stacking it, the area necessary for a 2D-Code can be relatively small. With respect to standard barcodes, the implementation of two-dimensional reading technology leads to a limited increase in costs, provided that the structure of standard bar codes remains unchanged. If this is not the case, special software drivers must be installed on the printing and reading devices.
1988 - 1995: Development
of the first Matrix
Codes, such as Data Matrix and MaxiCode.
At the same time, a series of codes were developed which can no longer be defined as barcodes, but as Matrix Codes. MaxiCode was specifically designed for omni-directional sortation of transport packages in a quick and reliable way. An error-correction algorithm guarantees the reliability of data. A quick image-processing system reads codes by means of a linear camera or a matrix camera whenever necessary.
Data Matrix, on the other hand, is particularly useful in applications requiring small spaces. Like MaxiCode, this code can be read omni-directionally. Data Matrix is very compact, reliable and can encode a great variety of characters and settings.
This is considered a major benefit in the pharmaceutical sector, as well as in different manufacturing sectors.
Examples of Barcode Applications
On the shop-floor of industrial plants Datalogic devices identify objects being manufactured, capture information from the process and transmit it to the company IT system, to make real-time control of time and processes possible. Datalogic devices identify the single products in the isles, production lines and warehouses, guarantee automatic and immediate monitoring of the production process, and supply all the necessary information to maximize precision, quality and efficiency.
Datalogic products are used to control and guide the movements of goods and people. In warehouses and transit areas of goods, centres of gathering correspondence and airports, national carriers and big international couriers, airports and airline companies, post offices and providers of logistic services find Datalogic to be the ideal partner to guarantee total traceability of each movement.
In supermarkets and shops Datalogic's readers enable consumers to pay without queuing at the cashier, enable the big chain stores to develop truly one-to-one promotions for their customers, and manufacturers of consumer goods to have a precise feedback on sales and the purchasing model of consumers.
OEMs require very reliable components that fit into their machines, minimising the integration effort and assuring the highest level of performance. Datalogic’s capability to define, develop and deliver specialised and customised devices in a fast and reliable way is crucial for OEMs in increasingly competitive markets.
Terminology - 1D-Code
|Bar||The dark element in a bar code symbol.|
|Space||The light element between two bars in a bar code symbol.|
|Intercharacter gap||In a discrete code, the space between the last bar of a character and the first bar of the following character.|
|Element||A bar or space in a bar code symbol.|
|Module||The narrowest element in a bar code. Wide bars or spaces are expressed in multiples of modules.|
|X Dimension||The width of the narrowest element.|
|Quiet zone||Also called light margin or clear area. It is the blank area before and after the barcode. The quiet zone Q is necessary for setting the reading direction of the bar code symbol. Thequiet zone must be at least 10 times the X dimension with anyway a minimum width of 2.5 mm. In scanner applications involving a large depth of field, the quiet zone must be wider: Q = 15 times the X dimension with a minimum width of 6.5 mm.|
|Barcode Symbol||The bar code symbol consists of a barcode, two quiet zones and an interpretation line. The bar code includes encoded data, which consists of coloured bars and blank spaces. The quiet zone precedes and follows the bar code and helps to identify the object to decode. The interpretation line is positioned below the bar code and translates all of the encoded information into readable characters.|