HP Color LaserJet 5500 Technical Reference Manual page 114

If the printer does not support the variable, the response is:
@PJL INQUIRE [LPARM: personality | IPARM: port ]
~ variable <CR><LF>
"?"<CR><LF>
<FF>
If a printer language-specific variable is not available
because that printer language is not installed or is invalid,
or if a port-specific variable is not available because that
port is not supported, the command will return an
appropriate error code if USTATUS DEVICE=VERBOSE is
enabled.
Note
The LPARM : personality option must be used when
requesting printer language-specific information.
The IPARM : port option must be used when requesting
port-specific information.
Example: Using
This example requests the current print environment
settings for RET, PAGEPROTECT, RESOLUTION,
INQUIRE to Request
PERSONALITY, and TIMEOUT. The printer response for
Feature Settings
this example is listed below.
<ESC>%-12345X@PJL <CR><LF>
@PJL COMMENT ***Inquiring About <CR><LF>
@PJL COMMENT Environment Settings*** <CR><LF>
@PJL ECHO 02:18:23.9 05-30-92 <CR><LF>
@PJL INQUIRE RET <CR><LF>
@PJL INQUIRE PAGEPROTECT <CR><LF>
@PJL INQUIRE RESOLUTION <CR><LF>
@PJL INQUIRE PERSONALITY <CR><LF>
@PJL INQUIRE TIMEOUT <CR><LF>
<ESC>%-12345X
For the HP LaserJet 4 printer, a sample printer response
for this example is as follows. Other PJL printers may
respond differently.
7-6 Status Readback Commands