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Chapter 3 Bar Codes
Quiet Zone
Both ends of the bar code structure require 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. Be sure to provide sufficient space on the form for the quiet
zones.
Start/Stop Codes
The start/stop code is a unique character identifying the leading and trailing
end of the bar code. The start/stop code is automatically produced with each
bar code. The start/stop code structure permits bidirectional bar code
scanning.
Data Field
The bar code symbol uses a series of wide and narrow bars and spaces to
represent standard alphanumeric characters. Each character is represented
by a different series of bars and spaces, both wide and narrow, but is always
16 units in width (for a wide to narrow ratio of 3). Each character starts with a
bar and ends with a space.
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
A mandatory modulo-127 check digit is inserted into the bar code to verify
accurate scanning.