~JO - Head Test Non-Fatal
Turns the printhead element test back off, so a failed element no longer stops the printer.
~JO is the other half of the ~JN switch and the state a printer powers up in.
With it active, the printhead element check reports no error, so a failed element
neither halts nor pauses the printer.
Syntax
~JOSupport
Accepted and skipped, because it configures the printer rather than the label. It cannot change the rendered output, and Labelary skips it too.
This is the other half of the ~JN switch, and no printhead exists for either half to act on. The renderer does not parse this command. It reports IGNORED_COMMAND at info severity, which does not reach X-Warnings. Labelary is also silent, so the rendered label is identical in both engines. — not pinned by a test
Labelary renders this command.
Parameters
~JO takes no arguments.
Behavior
That is the guide's account, and ~JO also clears the sticky error condition
~JN leaves after a failure. Labelary's reference reads the command the other way
round, as a test that pauses on failure. The two descriptions disagree, and
neither engine performs a test, so nothing observable depends on which is right.
~JO is the default, so it changes nothing without a preceding ~JN, even on
hardware.
Differences from the specification
Labelary against the ZPL II guide
Where Labelary — our compatibility target — behaves differently from the printed specification.
- Labelary says
~JOstarts a printhead test that pauses the printer if the test fails. The guide says the opposite:~JOturns the head test option off, is the power-on default, and stops the element check from reporting an error. The two sources disagree about what the command does, not about how the printer escalates a failure. — not pinned by a test
Example
The test made non-fatal again. The label renders exactly as it would without the command:
^XA
~JO
^FO50,50^A0N,40,40^FDHead test off^FS
^XZ
Related commands
~JNHead Test FatalTurns the printhead element test on, so that a failed element halts the printer.^JTHead Test IntervalSchedules how often the printhead element test runs, and which elements it covers.~HQHost QuerySends one of ten named printer reports back to the host.