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10.3 Miscellaneous Barcode Information
Height of a Linear Barcode
Industry standards suggest a height of either 6.5mm or 15% of the symbol length, whichever
is greater. Symbols of less than recommended heights may cause recognition problems.
Check Characters
Yes, we recommend the use of check-characters in barcodes. Operating without check-
characters is not safe and will lead to errors that are costly to correct. Using check-characters
positively affects data integrity, especially when character density is at the limits and/or
image quality is not at its best.
Prevent Interleave 2 of 5 Partial Reading
A partial scan of an Interleave 2 of 5 symbols may decode and cause incorrect data to be
read. To prevent partial scans on long symbols, the user should include bearer bars. These
bars run along the top and bottom edges of the barcode in the scanning direction. If a
partial scan of the barcode occurs, the scanning beam will hit the bearer bar and will not
decode. The bearer bar must touch the top and bottom of all the bars and must be at least 3
times as wide.
Another solution for the short scanning problem is to fix all Interleave 2 of 5 symbols to a set
number of digits. Zeros may be used to pad the data to the set number of digits. The
application program would then be set to only accept scans of the correct number of digits.
Finally, a check digit may be used. The Interleave 2 of 5 symbology has an optional check
character that uses a weighted Modulo 10 scheme. The check character is the last character
in the symbol and should be checked by the decoder and then transmitted with the data.
Since Interleave 2 of 5 must always have an even number of digits, the leftmost character
may need to be a zero when the check character is added. The standard check digit is
calculated by assigning alternating 3,1,3,1… weights to respective data digits. These weights
are then multiplied by their respective data digits and the products are summed. The check
digit is the digit that needs to be added to the sum to make it an even multiple of 10. An
example would be if the sum of the products was 37, then the check digit would be 3.