8
Bar code reader
User Information
Standard 3 of 9 code
Each character is represented by five bars and the four spaces
between them. The bar/space patterns are defined so that
exactly three are wide and the rest narrow. Characters are
separated by a narrow space. See
Table 1
.
The three wide and six narrow requirement makes each
character self-checking, but an additional checksum character
may be inserted in the message if desired. The checksum is
generated by adding the check values for all the message
characters, dividing by 43, and using the remainder to select the
checksum character. If a checksum is used, the character is
placed after the message characters.
When a checksum is used, the bar code reader verifies that the
checksum in the message matches the checksum calculated
from the message characters, but does not include the
checksum character in the returned message.
An extended 3 of 9 code includes the complete ASCII character
set, but it is
not
read by the bar code reader.
Table 1
Standard 3 of 9 code properties
Character set
Capital letters: A to Z (check values 10 to 35)
Numerals: 0 to 9 (check values 0 to 9)
Other characters:
- . space $ / + % (check values 36 to 42)
Message length
Variable
Checksum
Optional