What is the name given to a variety of rotary devices used in the Navy?

The correct answer is "Synchronous." In the context of Navy operations, a variety of rotary devices are often referred to as synchronous devices. These devices are essential for precise control and accurate measurement in various applications, including navigation and positioning systems. Synchronous technologies are utilized due to their ability to operate at a constant speed and maintain phase relationships, which is crucial for the coordination and synchronization of different systems aboard naval vessels.

Synchronous devices can encompass a wide array of elements that perform various functions, and their reliability and precision make them a favored choice in military and naval applications. The nature of synchronicity in these devices means that they consistently align with a timing reference, enhancing the effectiveness of the overall system they are part of.

Other options, while related to technology and mechanical systems, do not specifically pertain to the category of rotary devices widely used within the Navy in the same context as synchronous devices.