What are the three requirements when a K-card is annulled?

The three requirements when a K-card is annulled encompass essential communication and operational protocols to ensure safety and coordination among train crew members.

Stopping the train is a critical first step, as it ensures that any potential risks associated with proceeding under the annulled K-card status are mitigated. Knowing the train's location is important for accurately relaying information to other crew members and ensuring that the crew can effectively manage their operations. Informing the engineer in person serves to provide direct communication, allowing for any immediate questions, clarifications, or instructions to be conveyed clearly. This face-to-face interaction is vital in high-stakes environments like train operations, where miscommunication can lead to serious safety issues.

The other options do not fully encompass the required protocol as outlined in this context, highlighting specific lapses in the communication method or the actions taken upon annulment, which are crucial for effective train management and safety.