Rockwell Automation 2755-L7, -L9 Scanners - Manual (Page 49)

Glossary
G–11
substitution error
This error can be seen in a mis–encodation, mis–read, or human operator
error. Characters are substituted with erroneous information. Example:
correct data is 1, 2, 3; substitution is 1, 2, 5. Substitution errors are usually
the result of bar code labels with printing defects. Substitution errors are
extremely difficult to determine and are usually not found until the data has
been processed and an obvious data error is noticed.
symbol
A combination of characters including start/stop characters and check
characters, as required, which form a complete scannable entity.
symbol density
The number of characters per linear inch.
symbol length
The length of the symbol measured from the beginning of the quiet area
adjacent to the start character to the end of the quiet area adjacent to a stop
character.
U
unattended system
A Scanner/decoder combination that is triggered, or activated, by an external
source such as a computer, PLC or mechanical switch.
UPC
Universal Product Code. The standard bar code symbol for retail food
packaging in the United States.
V
valid read
A scan that when processed by a decodder, satifies the follwowing
parameters:
•
Belongs to an enabled symbology
•
Field length (number of characters)
•
Fields per scan
•
Capture count