A flexible cord used with grounding type equipment shall contain an equipment grounding conductor.
Adapters which interrupt the continuity of the equipment grounding connection may not be used.
Attachment plugs and receptacles may not be connected or altered in a manner which would prevent proper continuity of the equipment grounding conductor at the point where plugs are attached to receptacles. Additionally, these devices may not be altered to allow the grounding pole of a plug to be inserted into slots intended for connection to the current-carrying conductors.