Under what condition is a two-way device required to be disarmed?

A two-way device must be disarmed whenever the devices are to be separated to ensure safety. This procedure is crucial because disarming the device prevents unintended activation or engagement that could lead to accidents or unsafe conditions during the separation process. The risk of accidental triggering increases when coupling or uncoupling trains, hence the requirement for disarming at that time to maintain operational safety.

While reduced speed, maintenance checks, and nighttime operations may involve other procedures and safety protocols, they do not necessitate the disarmament of a two-way device in the same way that separating the devices does. Therefore, the correct condition reflects a fundamental safety measure essential for the efficient and secure operation of train handling.