Blinkenlights

"ACHTUNG! ALLES TURISTEN UND NONTEKNISCHEN LOOKENSPEEPERS! DAS KOMPUTERMASCHINE IST NICHT FÜR DER GEFINGERPOKEN UND MITTENGRABEN! ODERWISE IST EASY TO SCHNAPPEN DER SPRINGENWERK, BLOWENFUSEN UND POPPENCORKEN MIT SPITZENSPARKEN. IST NICHT FÜR GEWERKEN BEI DUMMKOPFEN. DER RUBBERNECKEN SIGHTSEEREN KEEPEN DAS COTTONPICKEN HÄNDER IN DAS POCKETS MUSS. ZO RELAXEN UND WATSCHEN DER BLINKENLICHTEN."

Originally, Blinkenlights were simply diagnostic lights on electronic devices. In some places, they still are. But that's boring.

Thanks to signs in "mock German" that appeared in various computer rooms in the 1950s, Blinkenlights became something for non-technical people to look at, instead of touching something they really shouldn't touch. From there, it was only a matter of time – less than a decade – for Blinkenlights to become a visual shorthand for high technology in general, not just computers ... and, in Hollywood, they were always blinking.

As computers became more ubiquitous, the trope faded from the public consciousness. (Real Life 21st-century mainframes don't even have diagnostic lights any more, at least not where people can see them.) Nowadays it's used in works that purposefully invoke Zeerust, always paired with Beeping Computers.

Wikipedia has a page about Blinkenlights. The Jargon File has a page about them, too. And so does the Urban Dictionary.

Not to be confused with illumination for Winken, Blinken and Nod.

Film

 * The Q-Bomb in The Mouse That Roared was covered in Blinkenlights.

Live-Action TV

 * Shown in The Prisoner episode "The General". is a plot point.
 * Star Trek: The Original Series faked Blinkenlights in Engineering, by sliding cutout screens back and forth behind backlit wall transparencies.
 * Knight Rider's KITT had a simplified set of Blinkenlights inset into his front bumper.

Video Games

 * "Blinken Lights II", from Keep Talking and Nobody Explodes, is an exotic puzzle that combines blinkenlights (as the name suggests), Morse code and the Simon game.