Printronix LQH-HWTM - Manual (Page 109)

Code 128A, 128B and 128C
109
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 codes identify the leading and trailing end of the bar code. Each
of the Code 128 subsets uses a unique start code and a common stop code,
both automatically provided by the IGP.
Code 128A Data Field
Although the command field does not allow the selection of Code A, the IGP
does encode these characters if found in the data.
Code 128B Data Field
The bar code symbol uses a series of varying width bars and spaces to
represent an extensive character set (96 ASCII characters and seven control
characters). The bars and spaces vary in width from one to four modules.
Each character consists of three bars and three spaces that total 11 modules.
Code 128C Data Field
The bar code symbol uses a series of varying width bars and spaces to
represent 100 pairs of numeric digits (00 through 99) and 3 control
characters. The bars and spaces vary in width from 1 to 4 modules. Each
character consists of three bars and three spaces that total 11 modules.
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-103 check digit is automatically calculated and inserted in the bar
code symbol. The check digit verifies accurate scanning. The start code is
included in the check digit algorithm.