In 1909, radio pioneer Charles “Doc” Herrold made his first broadcast in what would soon become KCBS news radio, the world’s first broadcasting station. Even though he didn’t invent radio itself — Marconi did — Radio quickly became a powerful disseminator of culture, entertainment and, as 40 years of NPR attest, necessary critical thinking. But how does radio broadcasting actually work? In 1937, the Handy (Jam) Organization (which you might recall) produced On The Air, a fascinating piece of vintage edutainment explaining exactly that, from how the microphone converts sound waves into electrical currents to how audio waves travel from studio to audience, in under 10 minutes.

For more on how radio revolutionized modern communication, see Anthony Rudel’s excellent Hello, Everybody!: The Dawn of American Radio.