METHOD OF TELEVISION BROADCASTING WITH PROTECTION AGAINST UNAUTHORIZED RECEPTION AND SYSTEM FOR ITS REALIZATION Russian patent published in 1994 - IPC

FIELD: television equipment. SUBSTANCE: method includes operations for isolation of synchronization pulses out of video signal, formation of new coded synchronization signals with their subsequent mixing into video signal, transmission of coded video signal over communication channel, extraction of coded synchronization signals from received video signal of formation of standard mixture of synchronization pulses and its connection with video signal. At transmitting side method includes operations of formation of new bipolar synchronization pulses, of formation of signal of first pseudorandom sequence, of signal of second pseudorandom sequence and of signal of third pseudorandom sequence. Then operations of addition of first and third PR sequences by their alternation and modulation of signal of bipolar synchronization pulses with signal of alternated PR sequence for generation of new coded synchronization signals are carried out. At reception side method involves operations of formation of signals of auxiliary frequency, of frequency of lines, fields and frames, of binary quantization of received video signal, of extraction of signal of frame synchronization pulse, of setting of phase of signals of frequency of lines, fields and frames in compliance with phase of frame synchronization pulse, of formation of signal of number of subscriber and of its comparison with signal of current phase position of formed signal of frame frequency with formation of comparison signal. After this operations of addition of comparison signal with binary-quantized video signal, of comparison of obtained summary signal with preset threshold value and of formation of signal of permission for scanning of coded video signal are conducted. System for realization of proposed method has input buffer, amplitude selections, phase discriminators, low-pass filters, voltage controlled generators, pulse generators, synchronization pulse former, keys integrator, unit for isolation of standard and input of new synchronization pulses, output amplifier, communication channel, referencing unit, selectors of field pulses, former of payment signal, payment memory unit, switch, selector of pulses of synchronization signal of receiver, integrator, selector of new synchronization pulses, decoder of payment signal, AND gate, coincidence circuit and pickup of subscriber's number. EFFECT: novelty of approach lies in insertion of coding of synchronization pulses by payment signal and their masking by means of series of pseudorandom sequences. 4 cl, 11 dwg