Which of the following best describes an isolated power supply?

An isolated power supply is best described as an ungrounded power source with isolated output wires. This characteristic is critical in the context of fireworks and special effects operations because it enhances safety by minimizing the risk of electrical shock or unintended activation of pyrotechnic devices.

When a power source is ungrounded, it means there is no direct electrical connection to the ground for safety. This isolation helps prevent faults from propagating through the system, reducing the chance of electrical hazards in a pyrotechnical environment where precision and safety are paramount. The isolated output wires ensure that if there is an overcurrent or malfunction, it does not create a path that could energize other conductive objects or surfaces, further enhancing safety.

In contrast, the other choices describe aspects that do not accurately represent an isolated power supply. For instance, grounded power sources could pose a risk if faults occur, and describing the supply solely based on its application, such as charging pyrotechnic devices, does not capture the essential electrical characteristics that define isolation. Therefore, the ungrounded aspect coupled with isolated output wires aptly encapsulates what an isolated power supply entails within this specialized field.