What device prevents power from being supplied to both the primary and alternate power source on an SDC?

The device that prevents power from being supplied to both the primary and alternate power source on a Submersible De-watering Controller (SDC) is a positive locking bar. This mechanism is specifically designed to ensure that only one power source can be actively supplying power at any given time, which is crucial for preventing potential electrical faults, equipment damage, or safety hazards.

When the positive locking bar is engaged, it physically obstructs the pathway for power from the inactive source, ensuring that there is a definitive separation between the two power sources. This locking mechanism offers a reliable and safe way of switching between the primary and alternate power supplies, enhancing the operational integrity of the system.

In contrast, the other options, while they may serve important functions in different contexts or devices, do not specifically fulfill the requirement of preventing simultaneous power supply in an SDC setup.