Practically everything on the card has significance. Along the top are the main colors of white, yellow, cyan, green, magenta, red, blue and black. There are triangles on each of the four sides of the card to check for correct overscanning of the picture. The standard greyscale and frequency response tests are found on either side of the central picture. On the updated Test Card J, the 'X' on the noughts-and-crosses board is an indicator for aligning the centre of the screen. A person was used so it would look obvious if skin colour is wrong. Even the garish colors of the clown have a purpose, according to the BBC, because their juxtaposition is such that a common transmission error called chrominance/luminance delay will make the clown's buttons show up white.
Often, the name of the broadcasting channel will appear in the space, underneath the letter 'F'.
The card was developed by BBC engineer George Hersee, who died in 2001 at aged 76. The girl in the picture is Carole, one of Hersee's daughters.
Today the test card is rarely broadcast. This is due to the onset of 24 hour television. The last known occasion that the card was broadcast on British screens was Friday, 9 January, 2004, when early morning tests were carried out on BBC 1 and BBC 2. BBC 2 still regularly goes off-air for two or three hours each night, but usually broadcasts pages from Ceefax rather than test cards.