Amazing article at The Atlantic on how baseball games were shown to large crowds using manual displays, lights and puppets. The modern ESPN online gamecasts are very similar to how the games were shown to crowds back in the early 1900s.
There, a series of lights shone through the thin fabric indicate the progress and location of hits, base runners and fielders. At right in the photo are ball, strike, and out lights. This was not a one man job. Several controlled the indicators, one acted as announcer.