What should be done last when disarming the ETD system?

The correct procedure for disarming the ETD (Electronic Train Destination) system emphasizes the importance of communication checks before final actions are taken. By pressing the COMMUNICATIONS TEST/ARM button last, you ensure that all systems are functioning properly and communicate effectively with other components before shutting down the system.

This step verifies that the ETD is correctly set to a safe state and alerts the crew to any issues that could affect the system's operation. Following this, turning off the power or removing the ETD would happen afterward to ensure that the system has been confirmed as inactive and secure during the disarming process. Proper adherence to this sequence helps maintain safety and operational integrity.