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Chapter 3 Bar Codes
Quiet Zone
Both ends of the bar code structure have blank quiet zones. The quiet zones
must be at least 0.25 inches wide and completely blank to ensure accurate
reading of the start/stop codes and to prevent adjacent bar codes from
overlapping. You must provide sufficient space on the form for the quiet
zones.
Start/Stop Codes
Unique start and stop codes permit bidirectional scanning. Both start and stop
codes contain bars and spaces. They are automatically produced.
Data Field
The bar code symbol uses a series of wide and narrow bars and spaces to
represent numeric characters. The structure is 2 wide elements (bars or
spaces) and 3 narrow elements. In the bar code, two characters are
interleaved (paired); bars are used to represent the first character in the pair
and spaces are used to represent the second character in the pair.
German I-2/5 and ITF-14 are special cases of Interleaved 2/5 bar codes.
While Interleaved 2/5 has a variable data field, German I-2/5 is restricted to 11
or 13 digits, and ITF-14 is restricted to 13 digits.
Readable Data
The optional readable data field provides a readable interpretation of the bar
code data. It can be printed above or below the bar code symbol.
Check Digit
The modulo-10 check digit can be inserted into the bar code to verify accurate
scanning.
Interleaved 2/5 can be printed with or without a check digit, but German I-2/5
and ITF-14 have the check digit automatically included.