From memory I think that there was only a main circuit breaker at one end of the tram and if the driver was using that cab then I think he could have re-set the thing himself. There would be no point in having two in series as either or both would trip on an overload. Perhaps there were two and only one closed at a time to set the driving end. Normally the breaker would only trip if he was a bit too quick swinging the controller handle across the notches. The old DC overhead cranes I worked