Interleaved 2 from 5 Barcode Specification
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Code 2 of 5 Specification

The structure of the 2 of 5 barcode family is one of the simplest of the width-modulated industrial bar codes. There are three well known members of this family: the Industrial, Matrix and Interleaved. These three codes have the following similarities:

• Two wide elements per five-element character.
• Black bars and white spaces.
• Numeric character sets (0-9).
• Binary encoding: wide=1; narrow=0. A wide element is typically two to three times wider than a narrow element.
• Non-character start/stop, bar/space pattern.
• Even-parity character check.
• Optional message checksum character.

All of these 2 of 5 codes use five binary elements to encode each character. Two of the elements of each character are logic 1`s and, depending on the family member, are printed as wide bars and/or wide spaces. The consistent use of two wide elements out of five provides an easy method of character error checking.

The table below shows the binary-to-character encoding scheme used by these 2 of 5 family members. It is a weighted binary type with even parity. The least significant bit (LSB) is located on the left, and the parity bit follows the most significant bit (MSB) on the right. The fact that this code is a weighted binary type allows the decoder to calculate the encoded value, rather than performing a comparison search between decoded bit patterns and those located in memory.

2 of 5 Code Character Encodation

Another common feature of these codes members is the calculation of the optional message checksum character which encodes information about the number, value, and sequence of the characters in the message. The value of the checksum character is determined by the following six step procedure:

1. Identify even and odd positioned characters in the message with the right-hand message character ALWAYS defined as an even positioned character.
2. Sum the numeric values of the odd positioned characters.
3. Sum the numeric values of the even positioned characters and multiply the total value by three.
4. Sum the odd and even totals from steps 2 and 3.
5. Determine the smallest number which, when added to the sum in step 4, will result in a multiple of 10. This number is the value of the checksum character.
6. If Interleaved 2 of 5 code is being used, determine whether the total number of characters (message plus checksum) is odd or even. If odd, add a leading, non significant zero to the message to produce an even number of total characters as required by the symbology.

Interleaved 2 of 5 Code

An even higher information density can be achieved with the elimination of the intercharacter space. The Interleaved 2 of 5 barcode does this by interleaving characters encoded in the bars with characters encoded in the spaces.

The Interleaved 2 of 5 barcode is termed a "continuous" code because it does not use intercharacter spaces. Its continuous nature and its interleaving of the message characters make the Interleaved code the most complex of the 2 of 5 family to print and decode. The interleaving of characters also requires that an even number of characters be encoded.

When the message (including the checksum character, if used) contains an odd number of characters, a leading zero is added to obtain an even number of characters.

The Interleaved 2 of 5 barcode has the highest information density of the entire 2 of 5 family. Many inventory and data collections systems currently use both numeric and alphanumeric data to record part numbers and transactions. The 2 of 5 barcode family is capable of encoding numeric data. Thus, in those instances where alphanumeric data must be encoded, a different code must be selected. Out of the 2 of 5 family Interleaved 2 of 5 is the most common.

We have created an innovative Web based solution to the printing of Interleaved 2 of 5 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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