The 70s’ infinite monotone at the close of the broadcasting day (you still get it in China and some places). The mysterious static and squeal of the AM/FM/SW radio tuner, the bleep-blop sound effect of Atari’s original Pong video game. The click-clack-ring of the Olivetti typewriter. The 70-80s’ clickety-clickety dial of the rotary phone (that’s why it’s called a dial). The early 80s’ click-clack shuffle of the overhead slide projector.