"Everything you need to know is in the movies. You ought to see more movies."

-Steve Martin

Traditional movie theater booth used matched pairs of projectors, each running 2000 foot reels of film. At the tail end of each roughly 20-minute reel, skilled projectionists watched for a first “changeover” cue on the screen, started the other projector, and on the second cue, switched the lamp projection and the sound source to the other machine. The projectionists’ (dying) craft provided audiences a seamless performance.