"Das Blinkenlights," or just "blinkenlights," is a humorous term for any of the front-panel light-emitting diode (LED) lights found on computer and networking equipment. The concept behind das blinkenlights probably originated around World War II as a parody of the German language, the German facility for working with precision machinery, and their knack for posting assertive or domineering notices. To lighten the mood, workers in Allied machine shops during World War II posted parody safety notices on or around the machinery. The purpose of these signs was to warn the uninitiated away from messing with any machinery they didn't understand, and instead watch and enjoy the output.
In the early 1950s, these signs made their way into more scientific laboratories and research institutions. It is rumored that the first such notice to mention blinking lights appeared on an electron microscope at the Cavendish Laboratory at Cambridge University. Another version is reported to have made an appearance in 1955 at an International Business Machines (IBM) laboratory, and yet another at London University in the early 1960s. The generation of the parody language used in the sign is based on the fact that the English language has such strong Germanic roots that a parody version of German is easy to understand, read, and enjoy by English speakers.
Over the years after World War II, the sign continued to propagate and vary. What actually started as "blinkenlichten" eventually became "blinkenlights" as the latter became more commonly used in computer laboratories. Early computer programmers had implemented a series of lights on the fronts of their computers so they could see when the computer was performing specific operations.
The lights were meant to help them interpret the bus register states or the instruction counter while a program was running on the machine. As computers became faster, the blinking lights became nothing but a blur and were only capable of offering very general information. Most modern computers forgo the original blinkenlights now, and blinkenlights panels are typically only found on networking equipment such as routers, hubs, and patch bays, to indicate when throughput is occurring on a specific interface.
Still, das blinkenlights are much more enjoyable to look at than a plain black box, so a number of variations have evolved over time. In the 1980s, a parallel-processing computer called The Connection Machine was given a front panel that was nothing more than a programmable grid of LEDs; during its demo, it was programmed to display John Conway's mathematical Game of Life. Later, a personal computer named the BeBox made an appearance on the market, sporting rows of blinkenlights on its front panel.
Even though most computers ship with few or no blinkenlights on their front panels these days, the desire to brighten up an otherwise boring computer continues to take on new forms. Enterprising users have devised multiple methods of doing this. Some of those ways include lighted cooling fans visible through transparent panels, base lighting, and other modifications to the computer case and front panel.