Allen-Bradley 2-D Manual de usuario descargar pdf (Pagina 124)

G–10 Glossary

Publication 2755-6.4

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.

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%.

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Allen-Bradley 2-D Manual de usuario Pagina 124