What is meant by "duty cycle" when referring to RF exposure?

"Duty cycle" refers to the ratio of on-air time to the total operating time of a transmitted signal. This concept is crucial when considering RF exposure because it helps determine how much time an operator or bystander is exposed to radiofrequency energy. In practical terms, a transmitter that operates with a high duty cycle means it is transmitting a significant portion of the time, resulting in higher cumulative exposure to RF radiation. Conversely, a low duty cycle indicates that the transmitter spends more time in a non-transmitting state, thus reducing overall exposure levels.

Understanding duty cycle is particularly important for ensuring compliance with safety standards related to RF emissions and the operation of transmitters. This is why the third choice is the most accurate definition of "duty cycle" in this context.