A test pattern, or test card, was a screen represented by a card that was filmed and broadcast in between programs, usually during off-air times at night hours. It was used to calibrate and align the camera.
On many networks the test pattern would be preceded and ended by a rendition of the American national anthem, sometimes either accompanied by a flag flying in the wind, panoramic visions of the countryside or fighter jet formations, signifying the network was about to go on- or off-air for the day.
Today test patterns have been less used as there have been more TV shows in syndication, and other public access programs that air round-the-clock. However, they are still used in local UHF networks as well as some cable access shows, such as Christian channels that do not air on all hours.
One particular test pattern featured an Indian head. The "Indian head test pattern" became famous for its common use and is associated with classic black-and-white TV today. Nostalgia shops sometimes sell an "Indian head test pattern night light", as people often remember seeing the Indian head in the middle of the night if they accidentally left the TV set on.
- In one episode of Back to the Future: The Animated Series, Doc's head replaces that of the Indian.