nuts & bolts
Member
At stations with guarded operation and RA indicators, for example Euston, the guard doesn't use the buzzer but instead waves the green flag to the platform staff who operate the RA indicator. The slightly odd side of this is that the green flag is given when the staff door is still open so the train is not ready to depart.
In this scenario, the guard, by way of green flag/lamp shown is confirming door Interlock enabled?