HP 2500 HP PCL/PJL reference - Printer Job Language Technical Reference Manual - Page 127

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. Example: Using the ECHO Command 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. %-12345X@PJL @PJL COMMENT Using the ECHO command @PJL ECHO Testing 68394 10:57:06.4 %-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 Related Commands: INQUIRE, DINQUIRE, INFO, SET, DEFAULT, USTATUS EN Status Readback Commands 7-15