Rockwell Automation 2755-G6-D Scanner with RS-232 Option - Manual (Page 55)

Message Format Parameters
Chapter 7
7–2
A prefix is a subset of the preamble normally
formatted to some industry standard. It is represented
by a specific ASCII code. An example of a prefix is
the STX (Start of Transmission) code.
Scan the appropriate prefix label.
IA Prefix=None *
IB Prefix=STX
IC Prefix=SOH
Prefix