What is information on antique carbon arc projectors?

I use to operate these prjectors in the 70's-80's before they were replaced by 1500 watt zenon bulbs. Only the lamp housing was changed out, the projector and film part stayed the same. The carbon rods were replaced quite often. The film was split up in about 20 minute reals usually 5 to 6. When it looked like the rod would not make it we would change it. It was a gamble if you had a short real or commercial if a small rod would make it. These ran on a AC to DC motor generator. When I came abord we used a diode unit mutch quiter but the motor-generator where still kept and we could switch over if the diode unit failed. Witch never did in around 15 years. Peerless made the projectors. These were in the bay area California USA