What signal is used to indicate both a warning and to cease operations?

The correct answer indicates that a repeated high arm signal is used to convey both a warning and to cease operations. This type of signal is essential in crane operations and construction sites where visual communication is often necessary due to noise and the distance between workers and the operator.

The repeated high arm signal is recognized universally as a clear indication that attention is needed and that operations need to stop or be carefully approached. This is particularly important for ensuring safety around cranes, which can pose serious risks if not handled properly. By using a high arm signal, workers can effectively get the attention of the operator, indicating that there is a need to halt any ongoing maneuvers, thus preventing accidents.

In contrast, while other methods like using flashlights or a long blast of a horn may also serve as warnings, they do not necessarily combine the dual function of signaling for attention and indicating a need to stop operations in the same way as the high arm signal does. Similarly, waving both arms up and down could be misinterpreted and is not a standardized signal for ceasing operations; hence, it lacks the clarity and universality required in crane operations.