Electric signs and outline lighting systems must be grounded by connecting to which component?

The proper grounding for electric signs and outline lighting systems is achieved by connecting to the equipment grounding conductor. This conductor ensures a safe pathway for electrical fault currents to the ground, which is critical for protecting both the people using the system and the equipment itself. When a fault occurs, the equipment grounding conductor provides a low-resistance route that allows the excess current to safely dissipate into the earth, which can help prevent electric shock hazards and potential damage to the equipment.

Using the equipment grounding conductor is in accordance with electrical safety codes and standards, which prioritize the reliable grounding of equipment to enhance overall safety. This choice also helps maintain effective performance of protective devices, such as circuit breakers or fuses, ensuring that they operate correctly in the presence of faults.

The other options proposed do not fulfill the same safety functions. For instance, connecting to the neutral conductor does not provide the necessary grounding needed for safety and can lead to unsafe conditions. Similarly, connecting directly to the supply line or other conductors would not establish the intended safety mechanisms prescribed in electrical regulations.