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, having been supplanted by Extreme Graphical Representation. (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.

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

Film

 * The Q-Bomb in The Mouse That Roared was covered in Blinkenlights.
 * Lampshaded at Alpha Beta Base in Airplane II: The Sequel. They don't know what all those lights do, they just keep blinking on and off.

Literature
""You asked what I knew." His binary read-out lights rippled back and forth — a chuckle."
 * In the very first scene in The Moon Is a Harsh Mistress, the self-aware computer Mycroft ("Mike" to his friends) is described as using his blinkenlights to laugh:

Live-Action TV

 * Shown in The Prisoner episode "The General". is a plot point.
 * Star Trek: The Original Series: The set designers faked Blinkenlights in Engineering by sliding cutout screens back and forth behind backlit wall transparencies.
 * In the Space: 1999 episode "Voyager's Return", the device built to override Voyager's computer has blinkenlights that flash when it is connecting to or connected to the spacecraft... but not when the connection is terminated.
 * Knight Rider's KITT had a simplified set of Blinkenlights inset into his front bumper.
 * IRAC from the 1970s Wonder Woman TV series had blinkenlights where one would expect to see a monitor screen.

New Media

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

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.

Web Comics

 * In the defunct web comic Commedia 2X00, Lord only knows what half the stuff in Dottore's lab do; among the Cow Tools allegedly stored in boxes in his basement are full out shout-outs to famous technobabble, including turbo-encabulators, vgrep scanners, and Blinkenlights.

Real Life

 * The very earliest Personal Computers, including the groundbreaking Altair 8800, had no keyboard or monitor (or any way of connecting either). Programs were entered in raw binary via switches on the computer's front panel -- and their output was returned via a row of blinkenlights, also on the front panel.
 * Those annoying flashing blue lights on Netgear routers. You know what they are.