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What is Symbology?
A bar code symbology is simply a method of symbolizing or representing characters and numbers with bars, spaces, squares and dots. Just as Morse code uses audible dots and dashes to symbolize different letters and numbers, bar codes use visual marks to symbolize alphanumeric characters. Morse code was invented to be used across telephone wires to induce short and long audible beeps while bar codes were developed for electronic data entry.
There are several different symbologies in use today. Each one has its advantages and disadvantages. Some have better character density allowing more information to be encoded in the same physical space. Some symbologies have better encoding techniques (or algorithms) that prevent the patterns from being misinterpreted. While other symbologies incorporate error-correction methods that allow a bar code to be correctly read even if some of the mark is missing or destroyed!
Some common symbologies include:
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PosiCode
There are two styles of PosiCode, A and B, for each variant. Style B encodes information in a wider pattern than A with each center-to-center distance one more G-dimension than the corresponding pattern in A.
Click for more information on Marking the PosiCode Symbology.
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Limited PosiCode
Limited Posicode, as well as PosiCode A and B, are "position" based symbologies that decouples the width of the bars from their positions within the code. Limited PosiCode is usually implemented because of its increased character density. The patterns established for alphabetical characters in the Limited version are 1G shorter than each corresponding character in normal PosiCode.
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Code 39
Also called 3 of 9, mark is made up of bars and spaces that come in one of two widths, "wide" or "narrow." Nine elements consisting of five bars and four spaces make up each encoded character. Of these nine elements, three are always wide and six are always narrow.
Multi-width symbologies, such as Code 39, cannot be completed by marking with a single-width tool such as an indent marker. Consideration should be given to molding and/or casting, engraving, embossing, or laser for this symbology.
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Interleaved 2 of 5
This symbology is only able to enclode numeric characters, but does so efficiently; by encoding two numeric characters for each symbol it therefore will always encode an even number of characters. Any odd-sized numbers will automatically be padded by leading zeros. Since Interleaved 2 of 5 is a nulti-width symbology, marking with a single-width tool such as an indent marker will not work. Other direct-part marking methods include: engraving, molding and casting, embossing and laser.
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Code 128
Each Code 128 character consists of eleven 1X wide modules, where X is the width of the narrowest elements. Each symbol character is comprised of three bars alternating with three spaces, starting with a bar. Each bar or space (element) may consist of one to four modules. Since Code 128 is a multi-width symbology, marking with a single-width tool such as an indent marker will not work. Incorporating a a Code 128 mark into an injection-mold tool or using automated embossing, engraving, and orther variable width marking methods are ideal.
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