Rockwell Automation 2755 High Performance VLD Scanner - Manual (Page 55)

Glossary G–7
Spectral Response
The variation in sensitivity of a device to light of different
wavelengths.
Specular Reflection
Reflection of light from a surface at an angle equal but opposite to
the angle of incidence. See reflectance, specular.
Spots
Ink or dirt spots within the spaces or clear area of a bar code which
may reduce first read rate.
Start/Stop Characters
Bar code characters that provide the scanner with information on the
how the code is bounded and its orientation. The start character is
normally at the left end of a horizontal code and adjacent to the most
significant character. The stop character is normally at the end of a
horizontal code and adjacent to the least significant character.
Substitution Error
This error can be seen in a mis-encodation, misread, 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.
Symbology
The conventions, or rules, which govern the formation of characters
and strings in bar codes. The language of the bar code symbol.
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.
Valid Read
A condition in which a bar code has been successfully decoded.
VLD
Visible Laser Diode.