Test card
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A test card, also known as a test pattern in North America, is a television test signal, typically broadcast at times when the transmitter 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 SMPTE color bars). They would also typically be broadcast to a background of specially composed music, to avoid having to pay licensing fees for existing compositions. There is now a cult following for test-card music.
The most famous British test card is Test Card F which incorporates a colour photograph, used on the BBC and ITV from the beginning of colour broadcasts in the late 1960s. It was later updated as Test Card J, and for widescreen broadcasts as Test Card W. This test card has often been spoofed by comedians.
Formerly a common sight, test cards are now only rarely seen. Three 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.
- In developed countries such as the United States or the United Kingdom, 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.
- In North America, most test cards such as the famous Indian Head test card of the 1950s and 1960s have long been relegated to history. The SMPTE color bars occasionally turn up, but with most North American broadcasters now following a 24-hour schedule, this too has become a rare sight, and the switch from analog to digital broadcasting is expected to render this last test pattern obsolete.
- When there are in fact no standard programmes being broadcast on the channels that still do not have 24-hour programming, other, more informative features such as educational programmes, i.e. the BBC Learning Zone, and teletext-type programmes such as CLOSE, ITV Nightscreen and 4-Tel On View are often broadcast, the latter type acting as the better test-card substitute as they just roll continuously.
- However, on television networks and stations in most of the Third World countries, test cards are still seen because most television networks and stations in those countries do not have 24-hour programming.
See also
External links
- The Test Card Gallery (http://www.meldrum.easynet.co.uk/mhp/testcard/index.html)
- Television Test Cards, Tuning Signals, Idents and Clocks (http://www.pembers.freeserve.co.uk/Test-Cards/)
- Barney Wol's website (http://www.noctua.demon.co.uk/video/video.html) has details of the development of UK testcards F, J and Wde:Testbild