What is the "color plate" on the TV?

Regarding TV, I believe that everyone had a common doubt in childhood: What is the meaning of the "green plate" appearing on the TV every Tuesday? Its existence makes it impossible for us to watch TV programs all day. This doubt is accompanied by everyone's childhood, and until now, there are still many people who don't know what it means. Today, Xiaobian will come to explain it with everyone.

Television broadcasts did not take long. After the 1950s, television broadcasting was available in China. Beijing TV Station (the predecessor of CCTV) was the first television broadcast in China. After that, Taiwan was established throughout the country, but most of them broadcasted CCTV programs and inserted some local news. At that time, CCTV carried out equipment overhaul every Tuesday afternoon, so the local stations did not have the CCTV signal, and they also arranged to repair the equipment on Tuesday afternoon, which continued. Therefore, every Tuesday, many years ago, there will only be a “green plate” on our TV set, and we will not be able to watch the show.

This "plate" is called "PM5544 TV test card clock", which consists of parts of different colors, sizes, and shapes, and each part represents a different meaning.

â—† There are 9 kinds of test and sign signals in the center of the big circle, which are arranged from top to bottom:

● TV station logo, indicating the name of the broadcast TV station.

● Black and white square wave, used to check the transient response of the TV brightness channel.

● Color signal, there are 6 color bars below the black and white square wave, which are arranged in the order of yellow, cyan, green, purple, red and blue. It gives the TV viewer a total impression of color, and thereby adjusts the hue and color saturation, as well as checking whether the TV's automatic erasing circuit is normal.

● White center crosshair, white center crosshair on black background, horizontal white line width 1 line/field, a total of two lines; vertical white line center one, two sides symmetrically distributed four, a total of six. Used to determine the center position of the entire image, check for interlaced scanning, and static convergence.

● Standard time stamp, which has Beijing Standard Time broadcast in the black rectangular block on the sharpness line.

● The sharpness line has a total of 5 levels of 140, 220, 300, 380, and 500 lines. Located below the standard time in the Great Circle, it is used to observe and adjust the bandwidth of the TV's sharpness and color saturation.

● Gray level, below the sharpness line, has a horizontal band that gradually changes from black to white. It is a test strip for measuring gray levels. This test strip is divided into 6 levels according to the amplitude of the electrical signal, and the linear and white balance can be checked.

● TV station logo display area.

● Outside the color signal test chart around the circle, there are 15 squares on the left and right sides, each with a certain brightness and color saturation value. Used to check the performance of the color decoder.

â—† Black and white rectangular guard frame on both sides: used to adjust the amplitude of the line and field scan and the center position of the image. The aspect ratio of the test chart is the same as that of the color TV screen, which is also 4:3, so it can be used to check the aspect ratio of the TV. The vertical frame is used to check the synchronization separation and clamping.

â—† The white background of the gray background is in the guard frame. Except for the big circle pattern and the rectangular color strip signal around the circle, it is composed of the white square square pattern on the gray background. Its horizontal direction is 13 grids, the vertical direction is 17 grids, and the gray background brightness is 30% black to white. It can be used to check geometric distortion, nonlinear distortion, dynamic convergence and color purity.

In order to better understand the "PM5544 TV test card clock", we take "Shandong Education TV Station" as an example:

After reading this, do you have a feeling of “sudden realization”? Instant knowledge! China Home Theater Network () will continue to share more exciting content about home theater related technologies. Stay tuned!

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