The old trolley bus's and trams used to be controlled via a drum resistance controller it consisted of about a 100 contacts arranged around the edge of the drum and the resistance strips were also arranged around the periphary of the drum. The contact arm was driven by a pilot motor. This made for a very smooth acceleration and braking system. Much of the control gear was made by Alln West & Co Ltd Brighton makers of the old dashpot oil starters anybody remember them??
