Symbol LS 6000i Product Reference Manual page 133

LS 6000i Series Product Reference Guide
advised, selecting this option is an extreme measure
against misdecoding severely out of spec bar codes.
Selection of this level of security significantly impairs the
decoding ability of the scanner. If this level of security is
necessary, you should try to improve the quality of your
bar codes.
UPC/EAN SECURITY LEVEL 3
5-92