Not a dummy, the big dial actually works. It is connected with two telephones, an amplifying apparatus, and a loudspeaker. When the instructor dials a number, the loudspeaker reproduces, so that all may hear them, the typical sounds that will be heard; and the instructor explains to the pupils what they mean.Link
I write books. My latest is a YA science fiction novel called Homeland (it's the sequel to Little Brother). More books: Rapture of the Nerds (a novel, with Charlie Stross); With a Little Help (short stories); and The Great Big Beautiful Tomorrow (novella and nonfic). I speak all over the place and I tweet and tumble, too.