Abbott CELL-DYN 3200, Руководство оператора системы, Страница: 660 / 684

A-2
CELL-DYN ® 3200 System Operator’s Manual
9140181H—October 2001
Bar Codes
Overview
Appendix A
Understanding the Label’s Code
In all bar code symbologies, the code consists of elements (single bars or white
spaces) and characters (groups of elements that stand for numbers or letters). In
code 39, a commonly used symbology, each code character contains nine elements,
at least three of which must be wide. Wide elements (whether they are bars or
spaces) in this symbology have a binary value of 1. Narrow elements have a binary
value of 0.
Most contemporary bar code systems have several features in common. These
include the following:
• The Quiet Zone is the area immediately before and after the bar code symbol.
This zone enables the scanner to read the code properly.
• Start and Stop Characters indicate the beginning and end of the bar code
symbol. They allow the label to be scanned from either right to left or left to
right, ensuring that code information is transmitted correctly.
• Intercharacter Gaps act as spaces between each character in the bar code
symbol. Code 39 contains these gaps. However, there are other codes, such
as Interleaved 2 of 5, that do not use them.
• The Interpretation Line is an area at the bottom of the bar code label where
human-readable information can be placed. This may or may not be the same
data as in the label code.
• The Check Digit is an extra numeric character in the bar code that permits the
scanning device to mathematically determine whether it read the code
correctly. This keeps the error rate as low as one for every billion characters
scanned.