Printronix l7032 Manual De Referencia

 195

Code 128 includes three subsets: A, B, and C. All contain the same bar 
patterns, except for the unique start character instructing the bar code reader 
which subset is being used. Special characters are available for switching 
between the subsets in order to generate the shortest possible bar code. The 
Code 128 structure is shown in Figure 9 and described on the following 
pages.

Both ends of the bar code structure require blank quiet zones. The quiet 
zones should 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 are responsible for providing sufficient space on the 
form for the quiet zones.

Code 128 contains special characters which use unique start/stop codes to 
identify the leading and trailing end of the bar code. In the automatic mode, 
start and stop codes are generated automatically. In the manual mode, you 
must supply the start code, but the stop code is generated automatically.

DATA FIELD

QUIET

QUIET START

STOP

LOWER GUARD BAND

CODE

CODE

ZONE

ZONE

OPTIONAL READABLE DATA FIELD

HEIGHT

STARTING

POSITION

CHECK DIGIT

FIELD

DATA
FIELD

QUIET
ZONE

QUIET

ZONE

STOP

CODE

START

CODE

OPTIONAL

READABLE

DATA

FIELD

HEIGHT

STARTING

POSITION

GUARD

BAND

LOWER

CHECK

DIGIT

FIELD