Although the sign might initially appear to be in German and uses an approximation of German grammar, it is composed largely of words that are either near-homonyms of English words or (in the cases of the longer words) actual English words that are rendered in a faux-German spelling. As such, the sign is generally comprehensible by many English speakers regardless of whether they have any fluency in German. Much of the humor in these signs was their intentionally incorrect language.
Michael J. Preston recites the gem as being posted above photocopiers in offices as a warning not to mess with the machine in the first print reference from 1974. The sign is also reported to have been seen on an electron microscope at the Cavendish Laboratory in the 1950s. Such pseudo-German parodies were common in Allied machine shops during and following World War II, and an example photocopy is shown in the Jargon File.
The Jargon File also mentions that German hackers have developed their own versions of the blinkenlights poster, in fractured English:
This room is fullfilled mit special electronische equippment.
Fingergrabbing and pressing the cnoeppkes from the computers is allowed for die experts only!
So all the “lefthanders” stay away and do not disturben the brainstorming von here working intelligencies.
Otherwise you will be out thrown and kicked anderswhere!
Also: please keep still and only watchen astaunished the blinkenlights.
With dramatically rising CPU frequencies in computer processors, the traditional front-panel "blinkenlights" soon became useless for monitoring computations and diagnosing software bugs. Still, they remain useful for indicators of power on/off status, hard disk activity and network activity on most personal computers.
Very early computers had a tendency to 'fall over' meaning that they were unreliable. In order to know it was working, a set of lights were added that indicated the condition of the address bus and data bus, and sometimes the control bus. If the lights were blinking, the computer was doing something. If the lights stopped in a pattern, it had stopped doing anything, and the problem might be found at the binary address displayed by the lights. These displays were useful because many programs might take days to complete, and the outcome would only be known when the machine spat out a card with an 80 character answer.
Some computers had a diagnostic display very similar to many SciFi movies, where the blinking lights represented the high byte address (XX__) vertically, and the low byte address (__XX) horizontally on an 8x8 matrix of lights. The experienced diagnostics engineer could watch the program and be able to tell what memory it was using and therefore which part of the program it was running, based on the activity of the 'blinking lights'.
The original IBM PC could have a diagnostics card plugged into it that used LEDs to show what part of the memory it was using, and show the memory address and data code on 7-segment displays whenever the card was manually locked or automatically triggered.
The Connection Machine, a 65,536-processor parallel computer designed in the mid-1980s, was a black cube with one side covered with a grid of red blinkenlights; the sales demo had them evolving Conway's Game of Life patterns.
This word gave its name to several projects, including screen savers, hardware gadgets, and other nostalgic things. Some notable enterprises include Project Blinkenlights and the Blinkenlights Archaeological Institute. Also, a telnet site, called towel.blinkenlights.nl, has an ASCIImation of Star Wars Episode IV: A New Hope on port 23 and a BOFH excuse server on port 666.