Citizen Systems iDP-3550 - Manual (Page 76)

ESC "
−
" n
[Function] Specifying/Canceling the underline
[Code] <1B>H <2D>H n
[Outline] This command selects/deselects an underline. The underline is selected at n = 1 and
deselected at n = 0.
The space by the horizontal tab is not underlined.
ESC "4"
[Function] Specifying the red print
[Code] <1B>H <34>H
[Outline] This command prints its subsequent data in red. This command remains valid until the red
print deselection command is entered. Red and black characters cannot be mixed in one line.
ESC "5"
[Function] Canceling the red print
[Code] <1B>H <35>H
[Outline] This command deselects red print.