•
Whether there is a required check digit or character for the symbology,
Check digits/characters help ensure that symbol data is correctly
entered into the computer system.
•
Some symbologies have optional check digits or characters. It is
important to know whether a symbol contains an optional check
digit/character or not since the decoding software will not be able to
automatically determine this. In common applications, optional
symbology check digits/characters are not used. Codabar, Code 39,
and Interleaved 2-of-5 have an optional check digit/character.
•
Some symbologies have required check digits/characters. These
must always be present for a symbol to be valid. Code 128 and
UPC/EAN have a required check digit/character.
Complete specifications for these symbologies can be obtained from AIM USA
and the Uniform Code Council (UPC/EAN symbology). See “Additional
Resources” for addresses.
What is “verification” and how does it differ from “reading”?
In bar code reading, a scanner/decoder attempts to decode a bar code symbol. If
successful, the data is sent to a database. No judgment on quality is made.
Verification, on the other hand, measures a number of physical parameters of a
bar code symbol to determine its quality. Good quality bar code symbols will read
more easily and reliably than poor quality bar code symbols.
This is particularly true of symbols that are produced in one place then shipped to
another location to be read (such as shipping labels and product labels).
Handling, transportation, storage, and normal use can reduce a symbol’s quality.
Symbols that “read” just after they’ve been produced may be marginal in quality
and may not be readable at the point-of-use.
A bar code quality program, however, is more than just print quality. Many
industries have specific formats that must be complied with. Data in the symbols
must be correct and correctly structured. There are a number of requirements
that relate to the data and its representation in any customer or industry standard
that cannot be checked by automatic verifiers such as Quick Check
®
PC. A bar
code quality program must be properly set up and offer adequate training to all
operators.
Companies use bar codes to improve efficiency. Bar codes that can’t be read
lower efficiency. Verification ensures that symbols will be readable at their
intended point-of-use – whether it’s a retail store or an assembly line.
A number of large retail chains as well as some industrial companies have begun
instituting much more rigorous bar code requirements. Bar codes that don’t read
are simply not acceptable and customers have begun returning merchandise or
instituting chargeback policies.
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