What condition must be met before returning to normal operations after a call-on?

Returning to normal operations after a call-on requires that the entire train must be clear of the interlocking area. This condition is essential for ensuring safety and proper functioning within the signaling system. The interlocking area is critical because it contains the switches and signals that help manage train movements. If the train is not fully clear, there could be potential conflicts with other trains or signals, which may create unsafe conditions.

Ensuring that the entire train is clear allows for the resumption of standard operations without the risk of obstruction or accidents. Safety protocols are in place to prevent any situation that could endanger passengers or railway staff, making this a fundamental aspect of returning to normalcy after any call-on procedures.