On Design Observer today, Steve Heller uncovers the arcana of television test patterns, and if this item doesn't belong on Wikipedia, I don't know what does. Here are a few lines:

The origin of the pattern is a story of form following function. Aesthetics were irrelevant to the primary purpose, and the technical draftsmen who anonymously designed it could have never predicted that decades later it would become a nostalgic icon. The intent was to enable engineers, who in the so-called "pre-television" days were the only persons to actually receive broadcasts, to calibrate the extremely small, very crude black and white scans that became the TV picture. While the circular target may seem odd given the rectangular shape of even the earliest screens, in fact, the initial test patterns conformed to the circular shape of an oscilloscope that showed engineers the electrical equivalent of an image in the form of a wave. But there was an even more deliberate rationale.

Read the whole thing here.