RU2002377C1 - Device for masking and demasking of tv picture signal - Google Patents

Abstract

Usage: in television technology, in particular in methods of maximizing a television image signal to exclude unauthorized access to transmitted information over open radio channels in unicast, subscriber and other special television systems Summary of the invention: the method involves the formation of a subcarrier frequency, the following signals: 1) frame sync pulses, 2) pulse blanking pulses, 3} horizontal sync pulses, 4) pulse blanking pulses, 5} information pulses, ma a scanning signal, as well as transmitting a masked television image signal. To do this, a sequence of masking radio pulse signals, pseudo-random sequence signals and additional frame sync pulse signals is formed. In this case, the last two signals are logically multiplied and the envelope of the sequence of maximizing radio pulse signals, which are summed with the television radio signal, is determined in accordance with the shape of the received signal. The amplitude of the sequence of masking radio pulse signals is determined by the amplitude level of the synchronizing signals in the television image radio signal, and the spectrum of signals of the sequence of masking radio pulse signals is located in the spectrum band of the television image radio signals. The signals of the frame sync pulses synchronize the signals of the pseudo-random sequence and the signals of the additional frame sync pulses. For a color television picture signal, additional frame sync pulses are placed directly in front of the frame blank pulses. This reduces the bandwidth of the frequencies and thereby increases the masking degree of the television radio signal of the image V ©

Description

The invention relates to television technology and can be used to prevent unauthorized access to transmitted masked information.

In Fig. 1, a block diagram of a transmitting tea device for masking and unmasking television signals is shown; in FIG. 2 is a block diagram of a receiving portion of a device.

The television signal masking and unmasking device comprises a video signal source 1 on the transmitting side, the output of which is connected to the first input of the mixing amplifier 2, a sync generator 3, whose output is connected to the input of the video signal source 1 and the second input of the mixing amplifier 2, the output of which is connected to the first input of the module torus 4, the second input of which is connected with the output of the image carrier frequency generator 5, as well as the output stage of the transmitter 6. The output of the clock sync pulses of the clock generator 3 is connected to the input of the unit counter 7, the sync input of which is connected to the output of the horizontal sync pulses of the clock 3, the output of the counter 7 is connected through the standby multivibrator 8 to the first input of the key 9 and to the input of the pseudo-random pulse generator 10, the output of which is connected to the second input of the key 9, the output of the last the first input of the additional modulator 11, the second input of which is connected with the output of the generator 12 of the subcarrier frequency. The output of the additional modulator 11 is connected to the first input of the adder 13, the second input of which is connected to the output Odulov torus 4, wherein the output of the adder 13 is connected with the input of the transmitter output stage 6.

The television signal masking and unmasking device (see Fig. 2) contains, on the receiving side, a channel selector 14, an intermediate image frequency amplifier 15, the output of which is connected to the input of the video detector 16, an emitter follower 17, the output of which is connected to the input of the synchronization unit 18, a frame output the clock of the synchronization block 18 is connected to the input of the counter 19, the output of the horizontal clock pulses of the synchronization block 18 through the multivibrator 20 is connected to the clock input of the counter 19, the output of which is through the standby the vibrator 21 is connected to the control input of the key 22, the controlled input of which is combined with the input of the filter 23 and connected to the output of the channel selector 14, while the output of the filter 23 is combined with the output of the key 22 and connected to the input of the amplifier 15 of the intermediate image frequency, and the output of the video detector 16 is connected to the input of the emitter follower 17.

The device operates as follows.

On the transmitting side, the video signal from source 1 is fed to a mixing amplifier 2, into which, to form a complete television video signal,

 synchronizing and quenching, horizontal and frame pulses from the sync generator 3. The generated complete television video signal is fed to the first input of modulator 4, To another input of modulator 4

5, an image carrier frequency signal is supplied from the image carrier frequency generator 5. At the output of the modulator 4, an amplitude-modulated full television radio signal is generated. From the sync generator 3, the frame clock arrives at the installation input of the counter 7, setting its predetermined state. Horizontal sync pulses from the output of the sync generator 3 are fed to the sync input

5 of counter 7. A portable multivibrator 8 is launched from the output of counter 7, which generates an additional frame sync pulse, which is fed to the clock input of generator 10 of pseudorandom sequences of pulses and to the first input of key 9, to the second input of which a binary pseudorandom sequence is supplied.

From the output of key 9, a sequence of additional frame sync pulses is obtained, the occurrence of which is determined by a pseudo-random law, i.e. on key 9, the operation of logical multiplication occurs. An additional modulator 0 converts the signals from the output of the subcarrier frequency generator 12 and from the output of the key 9 into masking radio pulses, the spectrum of which is located in the spectrum of the full television radio signal of the image. The inputs of the adder 13 are fed, on the one hand, the full television image signal, on the other hand, masking radio pulses. As a result of the summation at the output of the adder 13, the complete masked television image signal is applied, which is fed to the input stage of the transmitter 6. matched with the antenna-feeder device .

5 On the receiving side, the full masked television image signal from the receiving antenna is fed to the input of the channel selector 14, from the output of which the television image signal of the intermediate frequency is fed to the input

the filter 23 and the controlled input of the key 22. From the combined output of the filter 23 and the key 22, the unmasked full television image signal at an intermediate frequency is fed to the input of the amplifier 15 of the intermediate image frequency, where it is amplified, and fed to the video detector 16. From its output, the full video signal image through the emitter follower 17 enters the synchronization unit 18, which extracts the horizontal and frame clock. The frame clock arrives at the installation input of the counter 19, setting it to a predetermined state. On the other hand, to the counter clock input 19 through the multivibrator 20 operating in a self-oscillating mode and synchronized by the horizontal sync pulses from the synchronization unit 18, additional horizontal sync pulses are supplied. When a portable pulse appears at the output of the counter 19, a standby multivibrator 21 is triggered, which, at the control input of the key 22, opens the latter. As a result, a filter 23 is cut in which the masking radio pulses are rejected in the passband of the intermediate-frequency amplifier, thereby unmasking the entire masked television image signal.

(56) Copyright certificate of the USSR No. 745016, cl. E 04 N 7/16, 1980.

Claims (1)

The claims DEVICE FOR MASKING AND DEMASKING OF THE TV SIGNAL OF THE IMAGE, containing on the transmitting side a video source whose output is connected to the first input of the mixing amplifier, a sync generator, the output of which is connected to the synchronization input of the video signal and the second input of the mixing amplifier, the output of which is connected to the first input of the mixing amplifier a torus, the second input of which is connected to the output of the carrier frequency generator, the output stage of the transmitter, on the receiving side a channel selector, a gap amplifier ary frequency, whose output is connected to the input of the video detector, an emitter follower whose output is connected to an input of the synchronization unit, characterized in that on the transmission side entered the first counter, whose output is connected to the input of the first multivibrator, whose output is connected to the input of pseudo-random generator im0 5 about 5 (3 pulses and the first key input, the output of the pseudo-random pulse generator is connected to the second input of the key, the output of which is connected to the first input of the second modulator, the second input of which is connected to the output of the subcarrier generator, and the output is connected to the first input of the adder, the second input of which is connected to the output of the first modulator, on the receiving side a counter, a second and third multivibrators, a key, a filter, the output of the frame sync pulses of the synchronization unit are connected to the counter setup input, the output of the horizontal sync pulses s of the synchronization unit - to the input of the multivibrator, the output of which is connected to the second input of the counter, the output of which is connected to the input of the third multivibrator, the output of which is connected to the first input of the key, the second input of which is connected to the output of the channel selector and the filter input, the filter output is connected to the key output and connected to the input of the intermediate frequency amplifier. 0te /