 One episode took place on a nuclear submarine and the producer  wanted the sound of a sub humming in the background. Sound effects  editor Greene, Robert V. (qv) called the Navy who told him that  nuclear submarines dont make any noise. Undeterred, he placed a  microphone inside an old IBM electric typewriter and recorded the  "whir and clicks" it made. The next day the producers loved it and  asked where he got it. He told them that some Navy guys in San Diego  had sent him a tape.