Which statement is true about modulated frequency ranges?

• A. It is always above 1000 Hz
• B. It is never changed during treatments
• C. It is typically in the range of 0-200 Hz
• D. It is equal to the carrier frequency

Answer: (C)

The beat or envelope frequency produced when two high-frequency currents interact is what actually modulates the tissue response. This modulated frequency is a low-frequency range, typically in the 0–200 Hz zone. That low range is chosen because it effectively influences nerve fibers and pain pathways while staying comfortable for the patient; high-frequency carriers provide the energy, but it’s the low-frequency modulation that drives the therapeutic effect.

So this statement is the best fit because it correctly describes how modulation works in practice: the modulation frequency is not the carrier frequency, and it is not fixed above 1000 Hz or kept constant regardless of treatment. The carrier frequencies are usually in the kilohertz range, while the modulation (beat) frequency used therapeutically sits in the 0–200 Hz range.