Symbol LS3478-ER, Справочное руководство

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Glossary GL-9
PDF417 An error correcting 2-dimensional multi-row symbol
developed in 1992 by Symbol Technologies, PDF417
symbols are constructed from 4 bars and 4 spaces over 17
modules. The symbol size is from 3 to 90 rows. There is no
specified minimum or maximum for X or Y dimension. With
at least the recommended minimum level of error
correction, the recommended Y dimension is 3X. With less
than the minimum recommended level of error correction,
the recommended Y dimension is 4X. A quiet zone of 2X is
specified on each side of a symbol. Because of delta
decode techniques, the symbology is immune from uniform
bar width growth. PDF417 supports cross-row scanning.
The intellectual property rights associated with PDF417
have been committed to the public domain.
Percent Decode The average probability that a single scan of a bar code
would result in a successful decode. In a well-designed bar
code scanning system, that probability should approach
near 100%.
Pitch Rotation of a bar code symbol in an axis parallel to the
direction of the bars.
Plessey Code A pulse-width, modulated bar code commonly used for
shelf marking in grocery stores.
Postnet Code Code developed by the U.S. Postal Service to assist in the
automatic sorting of mail.
Print Contrast Signal (PCS) Measurement of the contrast (brightness difference)
between the bars and spaces of a symbol. A minimum PCS
value is needed for a bar code symbol to be scannable.
PCS = (RL - RD) / RL, where RL is the reflectance factor of
the background and RD the reflectance factor of the dark
bars.
Programming Mode The state in which a scanner is configured for parameter
values (see
Scanning Mode ).
Quiet Zone A clear space, containing no dark marks, which precedes
the start character of a bar code symbol and follows the
stop character.
Radio Frequency Non-optical automatic identification devices that use radio
waves to transmit data.
Radio Frequency Data Communication (RFDC) Handheld or vehicle mounted units that send and receive
messages by radio frequency. Information from the units is
displayed on a screen for workers and allows real-time,
two-way exchange of data between terminals when one
terminal is mobile and the other is a host computer at a
remote location.
Radio Frequency Identification (RFID) The use of small radio transponders that are activated by a
reading transmitter. The transponder carries a unique ID
code or other information in its memory and can be read at
a distance without line of sight.
Radio Frequency Tag An electronic tag capable of receiving, storing and/or
transmitting digital information.
Reflectance Amount of light returned from an illuminated surface.