Test Card W
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Test Card W is a test card, an image used to determine the quality of a broadcast television picture. It is an updated 16:9 (1.78:1) widescreen version of Test Card F, which was created by BBC engineer George Hersee. Test Card W is similar to Test Card J, the latter being a 4:3 version. Both appeared for the first time in November 1999.
The colour-bars on the top and right of the image are the full 100 percent saturation version, unlike Test Cards F and J which use the 95 percent type. Extra mirrored arrow-heads on the central axis at the sides mark the positions of the middle 4:3 and 14:9 sections of the image.
As television is usually broadcast 24 hours a day, the test card is now rarely used. The last known occasion that this card was broadcast on British screens was Friday 9 January 2004, when early morning tests were carried out on BBC One and BBC Two. BBC Two still closes every weekday morning between 4.00 and 6.00 and during Educational Holidays, but pages from Ceefax rather than test cards were broadcast on these occasions until October 2012, and subsequently trailers and promos for various programmes have been shown.
BBC HD channel variant ('Test Card X') 
A modified version of Test Card W (sometimes referred to unofficially as Test Card X) was used on the now-defunct BBC HD channel. It was designed for 1080 line vision and includes the same picture of Carole Hersee and Bubbles the clown. This card could be viewed every two hours as part of the BBC HD preview slot. When viewed, it was enhanced with 5.1 surround sound tests. A BLITS tone is played alongside, which plays test tones at different frequencies from each of the different surround sound speakers, with markers (such as L, R, C, LFE, Ls, Rs) appearing inside some of the grey boxes of the testcard. BBC HD closed in March 2013; therefore Test Card X is no longer broadcast.
- "Hidden testcard on topup box". Digital Spy. 2008-01-13. Retrieved 2012-05-10.
- Quested, Andy. "A Christmas Present from the HD Channel!". BBC Internet blog. Retrieved 2013-12-21.
The test card seems to have been given the name "Test Card X" but not by us, it is in fact a modified high definition version of test card W
- Quested, Andy. "A Christmas Present from the HD Channel!". BBC Internet blog. Retrieved 2011-12-14.