HP 83751A Programming Manual page 250

Error Messages
311 -178, "Expression data not allowed;SHSS: No Default Step Sizes
Allowed (311)"
Indicates that the command "SHSS" was detected while the
instrument was using the HP 8350 compatible language. These
commands are accepted but no action is taken because the
instrument does not have this feature.
312
Allowed (312)"
instrument was using the HP 8350 compatible language. These
commands are accepted but no action is taken because the
instrument does not have this feature.
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