Bar code specifications

Interleaved 2 of 5

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Interleaved 2 of 5 specification
Data Type: Numeric (even number of digits only)
Bar Code Length: Variable
Checksum: Optional
Wide/Narrow bar width ratio: 2.4:1 - 3:1 (where 3:1 is the optimum ratio)

Interleaved 2 of 5 is a high-density bar code for encoding numeric-only data. The symbol length is variable and can be as long as necessary to store the encoded data.

The character set consists of 100 pairs of digits from 00 – 99, and a start and stop character.

Interleaved 2 of 5 can only be used for encoding an even number of digits. If you have an odd number of digits, you should insert a '0' at the beginning of the string.

The bar code is called 'interleaved' because the first digit is encoded in the bars and the second digit is encoded in the spaces. Each digit consists of 5 elements (two wide and three narrow ones) and is self-checking.

The complete bar code symbol consists of a quiet zone, the start character, the data string, and a trailing quiet zone. A check digit is optional and should be inserted before the stop character.

Encoding the symbol

The 10 individual numbers in the example must be turned into pairs of digits and converted to character positions in the bar code font. This is done by referencing the appropriate character arrangement table.

For fonts supplied in TrueType or Type 1 format, a rule can be followed rather than the Windows Character Arrangement Table. This rule is that for pairs of digits 00 – 93, add 32 to the digit pair to determine the character position. For pairs of digits 94 and over, add 67 to the pair. For fonts in Xerox or AFP format, the appropriate character arrangement table must be utlised.

Data	Start	12	34	56	78	90	Stop
Character position in font	171	44	66	88	110	122	172
Keystroke	«	,	B	X	n	z	¬

The final string should look like this:

Check Digit
A check digit can be used to mathematically verify that the bar code data is correct. With Interleaved 2 of 5 the check digit is optional, but if desired a Modulo 10 with weighting of 3, 1, 3 is used. The string must always be an even number of characters, so if the addition of a check digit gives an odd number, a zero should be added to the beginning of the string.

Note: the check digit is designated as Modulo 10, but is in fact a surplus to the number 10. Mathematically speaking, Modulo 10 is the remainder of the sum when the total is divided by 10.

Beginning with the left-most digit in the string, alternately multiply each number by 3 then 1 then 3 etc.

Data digit sequence 1 2 3 4 5 6 7 8 9 0 Weighting factor (multiply) 3 1 3 1 3 1 3 1 3 1 Total 3 2 9 4 15 6 21 8 27 0 = 95 The check digit is the digit needed to be added to the sum to make it an even multiple of 10. In this case the check digit is 5. START 0 1 2 3 4 5 6 7 8 9 0 5 STOP Modulo 10 (Weighting 3)

Character Arrangement Tables