What should be done after entering the ETD number on the HTD?

After entering the ETD (Electronic Train Data) number on the HTD (Handheld Terminal Device), the correct action is to push the COMM TEST button. This step is crucial because it initiates a communication test between the ETD and the on-board systems to ensure that the ETD is functioning properly and that data can be transmitted effectively.

Conducting a communication test validates that all systems are connected correctly and can exchange necessary information, reducing the risk of issues during train operations. This step is essential for confirming that the ETD is ready for use and that any potential communication failures can be identified and addressed before they affect train handling and safety.

While other options may seem relevant to troubleshooting or testing systems, the primary purpose right after entering the ETD number is to check communication functionality to maintain operational integrity of the train's braking system and overall safety management.