HP 83751A User Manual page 200

Error Messages
If an error condition occurs in the sweeper, it will always be reported to both
the front panel and HP-IB error queues. These two queues are viewed and
managed separately. The m key is used to view the contents of the front
panel error queue. The HP-IB query "SYSTem:ERRor?" is used to view the
contents of the HPIB error queue.
If there are any error messages in the front panel error queue, the front panel
MSG annunciator will be lit. Pressing the m key repeatedly until the MSG
annunciator turns off will empty the front panel error queue. The (MSG) key
has no affect on the HP-IB error queue. Emptying the HP-h3 error queue
has no affect on the front panel queue, therefore, it will not affect the MSG
annunciator.
There are some special error types that are called permanent errors.
Permanent errors remain in the error queues until the error condition is
cleared. Pressing the IIVISG) key will empty the front panel error queue, but
the permanent errors will be re-reported if the error conditions still exist.
In the HP-IB error queue, the permanent errors are re-reported after the
message, 0,"No error" is read using the "SYSTem:ERRor?" query or after the
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