HP Color LaserJet 5500 Technical Reference Manual page 123

Example: Using the
ECHO Command
Related Commands:
Use the ECHO command to synchronize status so that you
know the status you are receiving is the requested status.
To do this, send an ECHO command to the printer, and
then discard the incoming status messages until your
message is echoed back. Eliminate all data received from
the printer up to the echoed response string. For the
remainder of your print job, you can be sure that all status
messages you receive after your echoed message were
requested by your application. If you turned on USTATUS,
you may receive unsolicited status information at any time.
This example sends the Testing 68394 10:57:06.4
message using the ECHO command. After the application
receives the Testing 68394 response, all succeeding
solicited messages received during the current job are those
requested by the current application.
<ESC>%-12345X@PJL <CR><LF>
@PJL COMMENT Using the ECHO command <CR><LF>
@PJL ECHO Testing 68394 10:57:06.4 <CR><LF>
<ESC>%-12345X
A sample HP LaserJet 4 printer response for this example
is shown below. Other PJL printers may have different
responses.
@PJL ECHO Testing 68394 10:57:06.4<CR><LF>
<FF>
INQUIRE, DINQUIRE, INFO, SET, DEFAULT, USTATUS
Status Readback Commands 7-15