HP PCL/PJL reference - Printer Job Language Technical Reference Manual

EN Programming Tips for Using PJL 11-13
Spoolers equipped for bi-directional communications can monitor
printer status using the following commands:
Spooler Examples
The following examples show jobs used by spooling applications:
Jobs that monitor job progress and confirm job completion
Jobs that notify the user to load specific forms or paper
Jobs that control printer resources and print selected pages
Jobs that print a banner page followed by an application-
generated job (application specifies printer language)
Jobs that print a banner page followed by an application-
generated job (application does not specify printer language)
In each example, the indented lines indicate commands belonging to
a print file created by another application.
ECHO To synchronize status readback
information. The application should send
an ECHO command before any other
status readback commands; all status
responses before the returned ECHO
response should be discarded to ensure
proper synchronization.
STMSG To display a customized message and
take the printer off-line until the operator
presses the On Line, Continue, Job
Cancel, or Reset key. Returns the name of
the key that the operator pressed.
USTATUSOFF To turn off all unsolicited status before
specifying the desired USTATUS.
USTATUS PAGE To receive notification as each page lands
in the output tray.
USTATUS JOB To monitor job progress. Sends status
message when job has completed.