| 摘要 |
This invention deals with beam focus. The amplitude of an index signal varies with the focus conditon of the receiver tube. The aim of this invention is to control automatically the most suitable focus condition in the beam index-type color television receiver. The output of the phase comparison circuit enters into the low-pass filter and the matrix circuit to control the direct voltage level. In doing this, the focus of the electron beam achieves the most suitable condition. As the focus adjusts to the most suitable condition, the amplitude of the index signal always has a maximum value. So, we can effect the tint control.
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