| 摘要 |
<p>1. An arrangement for deciphering television pictures which were scrambled at transmission, by submitting the video signals consisting of separate components, for example signals having analog components of the MAC type to cyclic permutations from the adresses xi of points of cut produced by a pseudo-random digital address generator, the arrangement comprising for recreating the permuted signals two sets of analog or digital memories of the serial type whose outputs are connected to their inputs during the deciphering, these sets being used alternately and each comprising as many memories as there are separate components transmitted for each line, and the number ni of cells of each memory being equal to the length of the useful signal on which the circular permutation is effected, the said arrangement being characterized in that the clock frequency for the deciphering operation by means of a shift which is complementary to the shift effected at transmission is sufficiently high to ensure that the sum of the durations of the writing, the deciphering and the memory reading operations is less than or equal to two line periods.</p> |
