This is the only place I could find. which is about the tech power supply 60/120 volt system
647.7 Receptacles.
(2) All outlet strips, adapters, receptacle covers, and faceplates shall be marked with the following words or equivalent:
WARNING ? TECHNICAL POWER
Do not connect to lighting equipment.
For electronic equipment use only.
60/120 V. 1ac
GFCI protected
I do not believe it is an actual code requirement however, regular receptacles that are GFCI protected should be labeled identifying this. This is why GFI's come with the little "GFI protected" stickers.