Activation
Also: activated, called, 0001
The moment TRUST starts following a particular train for the day.
A schedule on its own is just a plan. A little while before a train is due to start, TRUST activates it: it picks today’s schedule, gives the run a train ID, and starts expecting reports.
The activation is what links the live train ID to the timetable’s train UID, so every later report can be matched back to the schedule.