Specialty step-down transformers are often _____.

Specialty step-down transformers are designed to convert high voltage levels to lower voltage levels, which makes them particularly useful for specific applications. Option B highlights that these transformers are often used for small tasks like doorbells and other signaling systems. This is correct because such applications generally require a lower voltage for safety and functionality, allowing the transformer to step down the voltage appropriately.

In these scenarios, safety is paramount, particularly in low-voltage applications where the risk of electric shock is minimized. Transformers designed for this purpose also typically feature insulated materials and components that protect both the device and the user. Specialty transformers can handle the specific voltage requirements needed for signaling systems, ensuring that they operate effectively without the hazards associated with higher voltages.

Other options may refer to different uses or characteristics that don't align with the typical applications of specialty step-down transformers, which primarily focus on scenarios needing low voltage, as mentioned in the correct choice.