What is indicated when buzzers are sounding OO when standing?

When buzzers are sounding OO while the train is standing, it indicates the need to start the train. This particular alert serves as a signal to the crew that the systems are engaged and the train is ready to move. Specifically, the "OO" sound typically means that all parameters are acceptable and that the operator can initiate movement safely.

Understanding this signal is crucial for train operations, as it ensures that the crew is aware of their status and can proceed accordingly. Other options, such as applying brakes, proceeding with caution, or making an emergency stop, are associated with different signals or situations and do not represent the correct interpretation of the "OO" buzzing sound while the train is stationary.