How did "Mehikon"
Congratulations to all on Victory Day!
- As you know, in Israel in the late 70s artificially removed color from television signals when broadcasting (this system was called “Mehikon” - “eraser”), so that the owners of expensive color TVs would not be conceited before the owners of black and white. But few know how it worked.
So, the television signal consists of lines (the screen consists of approximately 576 visible lines, there are 625 frames per frame, some of which are used for vertical synchronization,
15625 lines are transmitted per second - 25 frames per second.
At the beginning of the image line, there is a low-voltage pulse, called a sync pulse. So the TV knows when the line starts on the screen. Behind him comes a part of the color signal.
The device cut out the color signal at the beginning of the line (as we remember, it included the display), but left it in the picture!
This was noticed by some engineers, and a device was invented called the “Anti-Mechanic”, which was sold for one-tenth of the cost of a color TV at the time.
It inserted a color signal after the sync pulse, and the TV started to show color. The only problem was that the chrominance signal, as described above, was used for automatic adjustment, respectively, the signal could not be completely restored. Those who use the device often had to turn the adjustment knob on it (once every 15-20 minutes), since the color began to “float” due to a frequency failure.
- As you know, in Israel in the late 70s artificially removed color from television signals when broadcasting (this system was called “Mehikon” - “eraser”), so that the owners of expensive color TVs would not be conceited before the owners of black and white. But few know how it worked.
So, the television signal consists of lines (the screen consists of approximately 576 visible lines, there are 625 frames per frame, some of which are used for vertical synchronization,
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and should not be displayed). Синхронизация нужна для того, что бы можно было понять момент начала кадра (самая верхняя строка на экране, развёртка идёт сверху вниз слева направо) и начала каждой из строк,
15625 lines are transmitted per second - 25 frames per second.
At the beginning of the image line, there is a low-voltage pulse, called a sync pulse. So the TV knows when the line starts on the screen. Behind him comes a part of the color signal.
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This signal is used as a reference (which you can navigate when receiving), and also as an indicator of color transmission (if the program is black and white and the TV is color, then it can confuse parts of the picture with color, showing it where it is not necessary , and so he just turn it off). After the color signal is the visible part of the line image. Voltage is brightness, and the color signal itself is mixed into it. And now - how the Mekhikon itself worked. Цветовой сигнал является частью сигнала яркости, и выглядел на чёрно-белых телевизорах, как группы мелких точек в ярких местах, а цветные его отделяли.
The device cut out the color signal at the beginning of the line (as we remember, it included the display), but left it in the picture!
This was noticed by some engineers, and a device was invented called the “Anti-Mechanic”, which was sold for one-tenth of the cost of a color TV at the time.
It inserted a color signal after the sync pulse, and the TV started to show color. The only problem was that the chrominance signal, as described above, was used for automatic adjustment, respectively, the signal could not be completely restored. Those who use the device often had to turn the adjustment knob on it (once every 15-20 minutes), since the color began to “float” due to a frequency failure.
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Частота сигнала медленно изменяется из-за нагрева деталей и т.д. Со временем изменение становится существенным.