3.3.5   Isolator identification

The OFF position on all isolators must be clearly marked and should not be indicated until the contacts have opened to their full extent to give reliable isolation. Every isolator must be clearly and durably marked to indicate the circuit or equipment it protects. If a single isolator will not cut off the supply from internal parts of an enclosure, it must be labelled to draw attention to the possible danger. Where the unit concerned is suitable only for off-load isolation, this should be clearly indicated by marking the isolator "Do NOT open under load".