What happens when the master key is switched to On?

When the master key is switched to On, the expected outcome is that the trip indication light activates. This means that the system is acknowledging the activation of the master key, providing status feedback to the operator regarding the operational state of the system.

The trip indication light serves as an important visual cue, confirming that the system is ready to proceed with operation, which is generally a safety-critical aspect in many environments, including the Siemens systems mentioned in your practice test. Activation of this light ensures that operators are aware of the system’s condition and can take necessary actions based on its information.

In contrast, the other options do not reflect the appropriate function of the master key when engaged. Lowering trips or shutting down systems may relate to safety responses or operational protocols but are not directly associated with simply turning the master key on. Similarly, the initiation of train movement involves additional controls beyond simply switching the master key. Thus, the correct reaction to switching the master key to On is the activation of the trip indication light.