Rockwell Automation 2755-L7, -L9 Scanners - Manual (Page 41)

Glossary
G–3
clear area
A clear space, containing no dark marks, that precedes the start character of a
symbol and follows the stop character. That region of a document reserved
for OCR characters and the required clear space around these characters.
code
A set of rules governing how the bars and spaces of the symbol will represent
characters and groups of characters. bar code.
code medium
The material used to construct a machine readable code. Such materials may
be retroreflective or opaque.
code reader or scanner
A device that examines a spatial pattern, one part after another, and generates
analog or digital signals corresponding to the pattern.
contact scanner
A code reader that requires physical contact with the code medium.
continuous code
A bar code or symbol that does not use an intercharacter gap between
characters in the code. Code 128 is an example of intercharacter gap.
D
decoder
An unattended device used to decode, or make usable, a digital or analog
signal transmitted from a scanning device.
decoder logic
The electronic package which receives the signals from the scanner,
interprets the signals into meaningful data and provides the interface to other
devices.
depth of field
The distance between the maximum and minimum plane where a symbol can
be read.
diffuse reflection
Reflection of light in all directions. Diffuse reflection occurs from
non–glossy surfaces. (Also see specular reflection)
dirt
In paper, refers to the presence of relatively non–reflective foreign particles
embedded in the sheet. The size and lack of reflectance of the particles may
cause the optical scanner to mistake the dirt for inked areas.
discrete code
A bar code or symbol where the space between characters, intercharacter
gap, are not part of the code; as with Code 39. (Also see continuous code)