I am aware it is not a physical switch. Assumed it was short for switchover. Why do you get 500amp rheo brake during the rundown then? Auxiliary rheostatic braking?
According to the BR manual it's rheostatic braking obtained from the train heat winding via a step down transformer - which seems a cunning solution to the inability to generate rheostatic braking until the taps have run down.
Yeah, interesting I was just reading that bit in the driving manual. Which all rather confirms that they were designed to have a brake application made when 'notched up' if necessary.
