Circular Code 39
Circular Code 39 is a variant of Code 39 - Full ASCII that is typically used for printing onto disc-based media standards such as CD, DVD, or Blu-Ray. Because the height of the barcode is not integral to decoding the information, it is possible to use either the whole circle or an arc. The barcode reader that scans this symbol must be configured to perform Full ASCII character translations.
Code 39 is defined in ISO/IEC 16388 Information technology - Automatic identification and data capture techniques - Code 39 bar code symbology specification.
The symbol comprises the following elements:
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Leading quiet zone
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Start character (usually an asterisk [*])
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One or more pairs of symbol characters that represent data (including an optional check digit)
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Stop character (usually an asterisk [*])
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Trailing quiet zone
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Intercharacter spaces (one module wide) that separate characters within the symbol
Each Circular Code 39 data character is represented by nine elements: five bars and four spaces, three of which are wide and six narrow.
Circular Code 39 start and stop characters are used at the beginning and the end of the barcode message to signal a barcode reader that a Circular Code 39 barcode has been scanned. This character is commonly designated as an asterisk, but you can choose to have no start and stop characters at all or choose to let the data source specify either the start character or the stop character or both. The start and stop characters are not transmitted as part of the barcode and are not included in any check digit calculations.
Circular Code 39 shares the same properties as the Code 39 - Full ASCII barcode symbology. Additionally, it uses special two-character combinations from the 43-character set to allow for the representation of all 128 ASCII characters. In other words, you can encode any of the standard (not the extended) characters from the computer keyboard into a barcode as well as the ASCII control characters.
Circular Code 39 allows for an optional check digit that is based on the modulo 43 (mod 43) algorithm.
The recommended minimum symbol height for manual scanning is 5.0 mm or 15 percent of the symbol width (excluding quiet zones), whichever is greater. The quiet zones must be at least 10X wide, where "X" is the current X dimension.
Although Circular Code 39 has the advantage of representing all 128 ASCII characters, it does sacrifice barcode character density to do so. When you encode characters that are native to the 43-character Code 39 - Regular character set into Circular Code 39, your barcodes do not undergo any degradation in character density. However, because Full ASCII characters are represented by a two-character combination, they take up more space. For example, the word "SEAGULL" is encoded into the barcode as *SEAGULL*, but the word "seagull" is encoded into the barcode as *+S+E+A+G+U+L+L*, which takes about twice as much space.
Symbol Structure