According to the NEC, conductors of different systems, such as 120V power and 24V control circuits, are permitted to occupy the same raceway, cable, or enclosure under which of the following conditions?

• Only if all conductors have an insulation rating for the highest voltage present.
• Only if the control circuit is Class 1.
• Only if a barrier is installed between the systems.
• They are never permitted in the same raceway.