Which of the following types of signals must a signal person be knowledgeable about?

The correct answer highlights that a signal person must be knowledgeable about hand signals, voice signals, and radio signals, as these are the primary methods of communication used in construction and heavy lifting operations.

Hand signals are essential because they offer a visual means of communication that can be relied upon even in noisy environments where verbal communication may not be effective. Voice signals are equally important as they allow the signal person to provide real-time instructions and information to the operator and crew, especially during operations where immediate, clear communication is crucial. Radio signals are vital for instant communication over distances, providing a way to relay information quickly, which is especially beneficial in situations where the signal person is not in direct line of sight with the operator.

Understanding these three types of signals ensures that the signal person can effectively manage communication on the job site, enhancing safety and coordination during operations.