In the past and indeed up to quite recently, film studios often generated their own power. This was in the form of a d.c. voltage, usually at 120 V and mainly used because of the need to supply carbon arc sources used in the film industry. The basis of the 120 V was the importation from America of the lighting technology used in film studios. As the public supply authorities did not in general, supply d.c. voltage, it was necessary for the film studio to install large diesel driven generators. Associated with the 120 V systems used was the need to have much larger copper feeder cables than would be normal in the UK, due to the current being used. With the advent of much more sophisticated d.c. power ...