During the decades of analog television service, broadcasters transmitted a test pattern for a short period at the beginning or end of the broadcast day (sometimes overnight), to be able to adjust equipment and log required readings. In the early days of television, in fact, it was also very useful for consumers to be able to adjust their sets. The Indian-head test pattern was the most common one in the black & white era. The specific one you ask about was the Philips PM5544 test card, which was not commonly used in the US or Canada. It is an electronic signal injected directly into the transmitter rather than an actual card placed in front of a camera.