The old theaters that run a movie with two projectors, a projectionist has to stand right there to change projectors at the exact second so the audience never sees the break when one reel starts and one reel ran out. You have to look for the white dots in the top, right-hand corner of the screen. This is the warning. Watch the movie, and you'll see two dots at the end of a reel.

"Cigarette burns," they're called in the business.

The first white dot, this is the two-minute warning. You get the second projector started so it will be running up to speed.

The second white dot is the five-second warning. Excitement. You're standing between the two projectors and the booth is sweating hot from the xenon bulbs that if you looked right at them you're blind. The first dot flashes on the screen. The sound in a movie comes from a big speaker behind the screen. The projectionist booth is soundproof because inside the booth is the racket of sprockets snapping film past the lens at six feet a second, ten frames a foot, sixty frames a second snapping through, clattering Gatling-gun fire. The two projectors running, you stand between and hold the shutter lever on each. On really old projectors, you have an alarm on the hub of the feed reel.

Even after the movie's on television, the warning dots will still be there. Even on airplane movies.

As most of the movie rolls onto the take-up reel, the take-up reel turns slower and the feed reel has to turn faster. At the end of a reel, the feed reel turns so fast the alarm will start ringing to warn you that a changeover is coming up.

The dark is hot from the bulbs inside the projectors, and the alarm is ringing. Stand there between the two projectors with a lever in each hand, and watch the corner of the screen. The second dot flashes. Count to five. Switch one shutter closed. At the same time, open the other shutter.

Changeover.

The movie goes on.