The Radio Shack PC-4 was used in the first movie, primarily by Dr. Spengler in the first half. It can be seen after the library scene, and during the Ghostbusters commercial. The Calculator was originally made by Casio, but, in 1983 Radio Shack and Tandy both made versions of it. In the film, it was mated with a TRS-80 Cassette Interface.
