What must the train engineer do if a Call for Orders signal is displayed?

When a Call for Orders signal is displayed, it indicates that the train engineer must stop the train on their own. This type of signal is a clear instruction that requires immediate attention, signaling the engineer that there is a need for communication regarding the train's movements, orders, or changes in operation.

Stopping the train allows the engineer to safely assess the situation and receive any new instructions or orders. The importance of this procedure lies in ensuring that the train does not proceed without the necessary information, which is vital for operational safety and adherence to regulations.

The other options do not align with the appropriate response to a Call for Orders signal. Allowing the Automatic Train Control (ATC) system to stop the train is not guaranteed in every scenario presented by this signal, as the situation demands the engineer's direct action. Notifying the Trainmaster is a protocol that may occur later, but it should not precede the necessity to stop the train. Continuing at the same speed would directly contravene the indication of the Call for Orders signal, disregarding the operational protocols designed to ensure safety.