What must be ensured before making electrical connections during coupling?

Before making electrical connections during coupling, it is essential to ensure that the mechanical coupling has been completed. This is crucial for several reasons. The mechanical coupling is what physically links the train units together, ensuring that they can function as a single cohesive unit. If the mechanical coupling is not completed, there is a risk of disconnection during operation, which can lead to accidents or equipment damage.

Moreover, completing the mechanical coupling provides a stabilizing foundation for the subsequent steps in the coupling process, including establishing electrical connections. The integrity of the mechanical connection ensures that electrical systems, once established, can operate effectively without the risk of separation that might disrupt power supply or communication between train units.

While it is important for the train to be stopped and the crew to be in position for safety reasons, these factors do not directly pertain to the requirement for completing the mechanical coupling first. Similarly, while operational signal lights contribute to overall safety and communication, they are not a prerequisite for making electrical connections during this part of the coupling process.