| 摘要 |
When the invention is used in multi-standard colour-television receivers, it is intended to reach a decision, using predominantly digital means, between the three following types of received signal, SECAM, PAL, and monochrome, the probability of incorrect decisions being reduced and, in addition, it being intended to produce the signal for synchronisation of the line-frequency switch. Using the digital variable ZÄ for the offset of the instantaneous frequency of the SECAM signal, and using a second digital variable SIGMA +/- for the phase shift of the PAL colour burst, which is obtained either in an analog or digital manner, a parameter is obtained by addition with alternating mathematical sign, the magnitude and mathematical sign of which parameter indicate which standard was present in the preceding field and whether the line-frequency switch is correctly synchronised. According to the invention, the result of the magnitude test is used for controlling a state register. The position of this state register supplies on the one hand a selection signal which determines which of the two standards is tested. On the other hand, by decoding the position of the state register, in each case one signal can be obtained for driving the colour killer and for selecting the corresponding colour demodulator.
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