Symbologies – Choosing the right Bar Code

Bar Codes are symbols consisting of a series of bars and spaces printed on a label

retro reflective barcodeThe most common bar codes are symbols consisting of a series of bars and spaces which can be applied to packages, cartons, bottles, and other commercial products. The bars and spaces in each symbol are grouped in such a way to represent a specific ASCII character. The interpretation of these groups is based on a particular set of rules called “Symbologies”. Various symbologies have been developed for particular applications. Some examples are shipping and receiving, manufacturing, retail, healthcare, transportation, document processing and tracking, and libraries.

Currently there are more than 400 symbologies in use. Some are alphanumeric, while others contain the full ASCII set, or only numeric data. When deciding on a particular bar code, it is best to use a universal symbology that is supported by most manufacturers. In addition, one must consider the type and amount of data to be encoded, as well as the scanning and printing equipment.

 

Barcode Densities – 3 Types (High Density, Medium Density and Low Density)

For the most effective and reliable scanning with any input device, use the lowest bar code density possible that will print on a given area on the label or page. This will make it easier to print and allow a higher depth of field for scanning. When space is available, Code 39 and Code 128 are the best possible choices when implementing most bar codes solutions.

 

Code 3 of 9 ASCII

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Code 3 of 9

Code 39 is variable length and is the most frequently used symbology in industrial bar cpde systems today. The principal feature is to endcode messages usjing the full alphanumeric character set. Three of the nine elements (bars) are wide and six elements are narrow. The Code 39 bar code uses four special characters “$”, “/”, “+”, “%” which can be paired with alphanumeric characters to extend to the full ASCII character set. Listed below are the options for the Code 39 symbology.

  • FULL ASCII

Standard Code 39 contains only 43 characters (0-9, A-Z, $, $, /, %, +). Code 39 can be extended to an 128 character symbology (full ASCII) by combining one of the special characters ($, /, %, +) with a letter (A-Z) to form the characters that are not present in the standard Code 39 symbology.

  • CHECK DIGIT

A modulo 43 check character can be used to enhance data security for Code 39 symbols. The last digit of the symbol is assumed to be the check digit, and to verify the symbol.

  • APPEND

It is sometimes advantageous to break up long messages into multiple, shorter symbols. If the first character of a Code 39 symbol is a space (ASCII 32), the the scanned symbol is appended to a storage buffer. This operation continues for all seccessive Code 39 symbols with a leasing space being added to previously stored ones.

 

Code 128

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Codabar

Codabar is a variable length symbology capable of encoding 16 characters within any length message. Codabar can encode six special alphanumeric characters, capital letters A through D, and all numeric digits, Codabar symbology for any new applications today should not be considered except under unuusal circumstances because it is limited and out-dated. Listed below are the optios for the Codabar symbology.

      • Check Digit

A modulo 16 check character can be used to enhance data security for Codabar symbols.

      • Append

When this option is selected, a “D” stop character is used to indicate that the data ffrom the symbol shoudl be concatenated with data from an adjacent symbol with a “D” start character.

      • Traditional Names

The traditional names ascribed different starts and stop characters. The start characters are “a”, “b”, “c”, and “d”. The stop characters are “t”, “n”, “*”, and “e”. When deselected, the starts/stop characters are “A”, “B”, “C”, and “D”.

 

Code 93

Code 93 encodes the full 128 ASCII character set using 9 modules arranged into 3 bars with adjacent spaces. Two of the characters are check characters. Code 93 is similar to Code 39 but encodes more characters per inch. Code 93 encodes the full 128 ASCII character set and is encoded similarly to the extended Code 39.

EAN/JAN

  • EAN/JAN-13

is fixed length and is similar to the UPC-A symbology, but encodes a 13th digit. Also, the “12th and 13th” digits of an EAN-13, may represent a country code in its entirety or just the beginning of the country code, which may vary from 2 to 3 digits. The code 00-04 and 06-09 are assigned to the United States. The nominal height for the EAN/JAN-13 bar code is one inch. The reduced size is 80% of the nominal size.

  • EAN/JAN-8

is fixed length and is similar to the UPC-E code, but includes two more digits for the country code. The nominal height for the EAN/JAN-8 bar code is one inch. The reduced size is 80% of the nominal size.

Interleaved 2 of 5

Interleaved 2 of 5 is a variable length, even numbered, numeric bar code symbol. It is typically used in industrial and master carton labeling. The symbology uses bars to represent the first character and the interleaved (white) spaces to represent the second character. Each character has two wide elements and three narrow elements.

UPC – Universal Product Code

  • UPC-A (Universal Product Code-A)

is fixed length, is the most common bar code for retail product labeling and is seen in most grocery stores across the United States. The symbology encodes a 12 digit numeric only number. The first six digits are assigned from the Uniform Code Council (UCC) in Dayton, Ohio, the next five digits are assigned by the manufacturer, and the final digit is a modulo 10 check digit. The nominal height for the UPC-A bar code is obne inch. The reduced size is 80% of the nominal size.

QR Code

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Data Matrix Code

Data Matrix is a 2D, variable length symbology capable of encoding all 128 ASCII characters and a number of different character sets. Each Data Matrix symbol consists of a perimeter quiet zone, border with two solid edges and two dashed edges, and cells inside the border which are dark or light. The border’s two solid lines with data cells are used for symbol identification, orientation, and cell locations. Data Matrix can accommodats up to 500 MB per square inch with a data capacity of 1 to 2335 characters. Data Matrix has a high degree of redundacy and resists printing defects.

PDF417

PDF417 is a 2D variable length symbology that can encode virtually any letter, number, or character. Each character consists of 4 bars and 4 spaces in a 17 module structure. The name of the symbol is derived from the format of the code. PDF stands for “Portable Data File” and the “417” is derived from the module structure. Each PDF417 symbol consists of 3 to 90 stacked rows surrounded by a quiet zone on all four sides. Each row consists of a leading quiet zone, start pattern, left row indicator character, one to thirty data characters, right row indicator character, stop pattern, and trailing quiet zone. PDF417 supports text compaction, numeric compaction, and byte compaction that correlate the mapping between codeword values and decoded data. PDF417 can accomodate up to 340 characters per square inch with a maximum data capacity of 1850 text characters.

MSI Plessey

MSI Plessey is a variable length numeric symbology. Each character consists of four bars with intervening spaces for each encoded digit, one or two symbol check digits, and a reverse start code. MSI Plessey is primarily used in marking retail shelves.