An analogue scrambling scheme for television signals
V. Zacharopoulos, Ch. Mantakas, K. Dagakis, Constantine Caroubalos · International Journal of Electronics · 1985
A new technique is proposed for a time-domain analogue scrambler which can be used to protect television (TV) signals against unauthorized reception. With the new technique, time-domain permutation of picture segments does not require double buffering of the picture signal and is realized using only one random access memory (RAM). This is achieved using a scrambling algorithm, which allows readout and write in the same memory address during each clock period. An alternative scrambling algorithm is used in the case when a higher level of security is required. The scrambler was designed, constructed and tested in the laboratory. The effect of scrambling on the video spectrum is experimentally investigated and the results are discussed. Photographs of the scrambled and descrambled TV pictures are given to show the effectiveness of the proposed scrambler and the good quality of the reconstructed picture.