Rockwell Automation 2755 2D Hand-Held Scanner - Manual (Page 124)

G–10 Glossary
Publication 2755-6.4
O
One-Dimensional Symbology
Symbologies which encode data only in a linear or horizontal
dimension (X-dimension); the symbol’s vertical height
(Y-dimension) is redundant (e.g., UPC/EAN, Code 39).
Opacity
The capacity for material to interfere with transmission of light.
Overhead
The number of characters required for start, stop, and checking for a
given symbol (in PDF417, also left and right row indicators and error
correction codewords). For example, a one-dimensional symbol
requiring start/stop and two check characters contains four characters
of overhead. Thus, to encode three data characters, seven characters
are required.
P
Parameter
A variable that can have different values assigned to it.
PDF417
A two-dimensional, or stacked, bar code symbology which can
encode over one kilobyte of data per label and which represents data
in the form of codewords (values 0 - 928). Each codeword consists
of four bars and four spaces, for a total of 17 module widths;
modules vary in width from one to six element widths. The
symbology permits encoding up to 30 data columns and from 3 to 90
data rows. For ease of reading while still maintaining high data
density, codewords are encoded in three mutually exclusive
encodation sets, or clusters, with the same cluster repeating
sequentially each third row.
Percent Decode
The average probability that single scan of a bar code would result in
a successful decode. In a well-designed bar code scanning system,
that probability should appear near 100%.