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Test card

A test card is a television test signal, typically broadcast at times when the tranmitter is active, but no programmes are being broadcast.

The test card usually has a set of line-up patterns, enabling televisions to be adjusted to show the picture correctly. (Compare with color bars[?]). They would also typically be broadcast to a background of specially composed music, to avoid having to pay licencing fees for existing compositions. There is now a cult following for test-card music[?].

Formerly a common sight, test cards are now only rarely seen. Two things have led to the demise of the test card:

Modern microcontroller-controlled televisions rarely if ever need adjustment, so test cards are much less important than previously.
The financial imperatives of commercial television broadcasting mean that air-time is now typically filled with programmes and commercials 24 hours a day, and non-commercial broadcasters have to match this