Something not seen very often on television, if at all, is the television test card, also known as a test pattern in North America. Basically, it is a television test signal, typically broadcast at times when the transmitter is active but no program is being broadcast (often at start-up and close-down). These interesting pieces of technical design evoke the warm memories that we have for the early days of television, when TV stations actually shut down for a few hours every day. Yes, really!

Used since the earliest TV broadcasts, test cards were originally physical cards at which a television camera was pointed, and such cards are still often used for calibration, alignment, and matching of cameras and camcorders. Test patterns used for calibrating or troubleshooting the downstream signal path are these days generated by test signal generators, which do not depend on the correct configuration (and presence) of a camera.

Digitally generated cards allow vendors, viewers and television stations to adjust their equipment for optimal functionality. With the complete U.S. conversion to digital television signals, it is highly doubtful that any real test patterns (test cards) are in use today at TV stations.