Miscellaneous Barcode Information - KoamTac KDC20 User Manual

9.3

Miscellaneous Barcode Information

9.3.1 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.
9.3.2 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.
9.3.3 Prevent Interleave 2 of 5 Partial Reading
A partial scan of an Interleave 2 of 5 symbol may decode and cause incorrect data to be
read. To prevent partial scans on long symbols, you should include bearer bars. These
are bars that 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 can 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 which 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 needed 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.
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Revision 3.05.R6
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KDC User Manual