| 摘要 |
The encoding is carried out by means of a low-pass input filter (21), a first modulator (20), a second low-pass filter (19), a second modulator (18) whose modulating signal has a frequency which is pseudo-randomly modified over time, this signal being pseudo-randomly chosen from two signals with differing frequencies (45, 46), and an output filter (17). The generator supplying two signals consists of two phase-lock loop oscillators each including a frequency divider (7, 9) in the loop, which are controlled by a common reference-signal generator (3, 4) which itself consists of an oscillator of the same type (3, 4) controlled by the frame-synchronising signal of the television transmitter, the latter, together with the reference signal, also being conveyed to the pseudo-random generator (14) in order to control the times of change of modulating signal. …<??>The decoding is carried out in the same way in the reverse order. |
