HP Color LaserJet 5500 Technical Reference Manual page 261

STMSG Response
@PJL STMSG DISPLAY=" message " <CR><LF>
key <CR><LF>
<FF>
UEL
<ESC>%-12345X
USTATUS
@PJL USTATUS variable = value [<CR>]<LF>
Unsolicited Status Message (not a response, but returned when printer events occur)
@PJL USTATUS variable <CR><LF>
[1 or more lines of printable characters or <WS> followed by
<CR><LF>]
<FF>
USTATUSOFF
@PJL USTATUSOFF [<CR>]<LF>
PJL Command Summary B-5