35mm projectors - the standard projectors in commercial movie houses in the 40's and 50's - ran at 24 frames per second. And, at that speed, it would have been 90 feet a minute.

The projection booths contained two projectors. The film came on 15 to 20 minute reels and the projectionist had to do "change overs" from one projector to the next. They watched for "cue marks" on the screen to tell them when to do this.   The sound tracks were mostly optical. The projectors were made up of a "picture head" and a "sound head".   

The projectionist used a "rewind bench" to get each reel back to the start for the next show.   Films are said to be "heads" out, or "tails" out in orientation. (If they're tails out, they need to be rewound to the head).

The projectors had a "focus" knob and a "reframing" knob in case the film was "misframed". Behind the lens was a "mask" that had to be changed depending on the format of the film - flat or cinemascope ("scope").

At that time the projector lamps were probably not lamps at all, but carbon arcs which used "rods," like in a welding machine, that were struck together briefly and then pulled apart so that an arc of electricity flowed between them, making a very bright light.

Hope some of this helps.