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Codabar Specification

Codabar (sometimes called Code 2 of 7) is a discrete, width-modulated barcode that provides a character set for encoding numeric data (0-9) plus six special characters ($, -, :, /, ., +). There are four different sets of start/ stop characters (a/t, b/m, c/*, d/e) available for use with this code. This feature allows the start/stop characters to be used as the key to different data bases.

There are seven binary bits of information encoded in the bars and spaces of each character. There are two binary 1`s, or wide elements, in the field of seven elements for the numeric characters (0-9) and two special characters ($, -). One binary 1 is encoded by a wide bar while the other is encoded as a wide space. The remaining special characters (:, /, ., +) and the start/stop characters have three binary 1`s per character. These are encoded as three wide bars in the special characters and one wide bar/two wide spaces in the start/stop characters. The table below presents the complete character set for the Codabar code, showing the encodation of each character.

Unlike the other width-modulated codes, Codabar does not use common wide and narrow element widths to encode the logic 1`s and 0`s in the characters. There are, instead, a total of 18 different widths for bars and spaces specified by the symbology. This structure was designed to account for the printing errors characteristic of certain early printers, leading to printed symbols which could be easily read. Note that it also provided a constant character length regardless of whether two or three wide elements were used in the character.

Codabar is commonly printed at a high module resolution of 0.0065 in.(0.17mm), the highest module resolution used by any symbology. The information density at this module resolution is 11 characters per inch. When lower information density is allowable, or when printer capabilities necessitate a lower module resolution, Codabar recommends symbol magnification in 25% increments. For example, the first magnification results in a module resolution of 0.0081 in.(0.21mm) and an information density of 9 characters per inch.

We have created an innovative Web based solution to the printing of Codabar and other barcodes. Barcode Mill prints barcodes on Web pages which may be scanned when the page is printed out. Alternatively the barcode can be cut 'n' pasted to a graphics package.

Altek Instruments Ltd have a range of products designed for the data collection/automatic ID industries.

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