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Bar code reader
7
About bar codes
A bar code is a printed pattern of bars and spaces that encodes
information. The most frequently encountered bar code is the
UPC code (Universal Product Code) that appears on most
packaged products in the supermarket.
The information in a UPC symbol is not the price of the product;
it is simply a number that has been assigned to that product to
distinguish it from all others. The supermarket checkout
register obtains the price by looking up the code in a master list
(actually, the store computer does it).
The Agilent Bar Code Reader (BCR) reads and decodes several
different bar codes. The most useful one for general laboratory
use is the Standard 3 of 9 Code, which encodes both letters and
numbers and allows variable message length. The others may
prove useful in special cases. The preprinted labels available
from Agilent are in Standard 3 of 9 Code without a checksum.
See
Table 1
.
Bar code elements
All codes represent the characters as a pattern of dark bars and
light spaces. Some codes only distinguish between narrow and
wide bars, some have several possible bar widths, some use
spaces to encode characters, others use spaces only as bar
separators, and so on. Why so many different ways of
accomplishing the same simple task? They were developed by
different groups at different times and for different purposes.