| 摘要 |
<p>Signals are coded by the SECAM system, with an oscillation present during one part of each colour period whose frequency has a first value in one period, and a second value in the second one and is always the same in each second period. A switching signal generator fundamental frequency is the reciprocal of twice this period. First devices controlled by this generator separate from the chrominance signal one or the other of the two frequencies, depending on the generator phase. Second devices respond mainly to the first frequency and generate a continuous signal. Third devices respond to it and bring the signal generator back to the required phase, if the phase has been shifted.</p> |
