JPS6170883A - Centralized viewing control system in catv system - Google Patents

Abstract

PURPOSE:To affect effectively jamming in a television set and to exhibit as sufficient scramble effect by setting a synchronous time division signal slightly shifted from the television vertical synchronization and the time division signal of a random frequency as a jamming carrier. CONSTITUTION:In terms of a system for scrambling a picture by adding a jamming signal to a television signal, a distribution system unit for distributing a picture from a branching line 1 to each terminal is provided with two sets of jamming generators 10 and 11 and a control circuit 9 which receives and demodulates the control signal from the center to transmit PLL data to the jamming generators 10 and 11 in accordance with the decoded data. The jamming generator 10 causes a voltage control oscillator to generate the oscillation frequency sequentially set in a period shifted slightly from the television vertical synchronization, while the jamming generator 11 causes a voltage control oscillator to generate the oscillation frequency at random by period set in a period slightly shifted from the television vertical synchronization.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a centralized viewing fee system for centrally controlling the viewing of paid programs to subscribers in a CATV system.

[Prior art]

Conventional viewing control methods include the following. ■ Jamming method At the center that transmits the program, 2.5 MHz is set in advance from the video carrier frequency that is within the pay program channel band
Trap (interfering signal) that makes TV reception impossible by injecting a carrier having a level equal to or higher than the video signal level into a frequency approximately z high, and removes the injected carrier (interfering signal) only for subscribers who wish to watch. This method is equipped with a notch filter). ■ Trap method In a system that distributes signals to each subscriber's terminal by setting a tap-off point, traps are arranged according to the video carrier frequency of the pay channel being operated in the system, and a tap-off point is set to each subscriber's terminal. This method inserts a trap into the terminal section of the TV for channels that you do not wish to view. ■Addressable Terminal System In this method, terminals with addresses are lent to subscribers, and viewing control signals are received from the center, demodulated, decoded as data, and viewing is controlled on each subscriber's terminal. The above method has the following drawbacks. (i) In the jamming method, a trap is required to reduce the degree of influence on the video signal as much as possible in order to remove the interfering carriers present in the TV channel transmission band. Quite large and steep characteristics are required. Therefore, expensive traps are required, the resolution of the video image after interference is removed is adversely affected, and if the center frequency of the trap drifts due to temperature etc., it tends to appear as beat interference in the image, and the existing The disadvantage is that converters and traps can easily be used for eavesdropping. 01) In the trap method, the trap is installed at a tap-off distribution terminal that is connected to a coaxial cable strung on a utility pole or the like, so it is installed at a relatively high location. Therefore, not only is management and maintenance troublesome, but also the cost is high because a predetermined number of traps are prepared in advance, and the quality of the video signal is degraded by connecting a large number of traps. Above all, there is a physical limit to the number of traps, and a large number cannot be aggregated. ■ In the addressable terminal method, a descrambling system is built into the terminal device, so there is a possibility that the terminal device may be intentionally modified by a malicious user and a charge for which there is no contract is made. Not only is there a risk that the first set may be viewed by eavesdropping, but the subscriber's consent is required for management and maintenance purposes, and if the consent is refused, the terminal device d cannot be checked. Furthermore, there is a risk that an expensive loaned terminal device may be taken away by mistake or intentionally when the user moves. Furthermore, when a subscriber has multiple television receivers, a terminal device is required for each receiver. Furthermore, deterioration in image quality due to scrambling and descrambling cannot be avoided. As described above, the conventional method has various disadvantages in various aspects. Furthermore, recent T and V sets have become 11
As 1J playback is becoming more stable and highly selective, jamming can make synchronization unstable and make viewing difficult even when TV is detuned! It has become 1.

[Objective of the Invention 1] The present invention was made based on the above circumstances, and it leaves only the converter function in the subscriber's premises, and incorporates the functional part that controls the subscriber's viewing control into the distribution system unit. , we will provide a centralized viewing control method for a CATV system that is installed outdoors and avoids the above-mentioned inconveniences, and also allows jamming to work effectively on the TV set and achieve a sufficient scrambling effect. That is. [Structure of the Invention] For this purpose, the present invention provides two sets of jamming generation systems in a distribution system unit that distributes from a branch line to each terminal in a system that scrambles uniformity by adding an interference signal to a television signal. Receives control signals from the device and center 1! IIIL is equipped with a control circuit that sends PLL data to each jamming generator according to the decoded data, and one of the jamming generators transmits the PLL data applied to its PLL port to the TV! I! An oscillation frequency that is set sequentially within a period slightly different from the direct synchronization is generated in a voltage controlled oscillator in a time-division manner, and the frequency generated from the voltage controlled oscillator is generated by a local oscillator at a frequency of 300% relative to the TV video carrier frequency. The other jamming generator converts the frequency to a frequency that is ~500KHz apart, and the other jamming generator uses the PLL data given to its PLL circuit to generate a frequency that is slightly different from the TV vertical synchronization.
2. A voltage controlled oscillator generates an oscillation frequency set within a period of 2/3 or 1/3 in a random order every period, and the frequency generated from the voltage controlled oscillator,
A local oscillator converts the TV image carrier frequency to a frequency that is approximately the same or within several tens of KHz apart, and is superimposed on the TV signal as an interference signal. [Embodiment 1] Hereinafter, one embodiment of the present invention will be specifically described with reference to the drawings. FIG. 1 shows a distribution system unit, which is installed at the tap-off portion of a branch line 1 and distributes television signals to converters at the subscriber's premises via a drop line. Here, a television signal from a branch line 1 is input to a branching filter 4 via a branching device 3. The television signal from the duplexer 4 is sent via a variable resistance attenuator 6 to a transmission module 18 by a distribution type 7 corresponding to each terminal. Further, the television signal from the duplexer 4 is input to the FSKfi modulator 8, and its data signal component is extracted and input to the control circuit 9. From this control circuit 9, two sets of jamming generators 10. For It, P
LL data is sent. In the module 18, when the output signal from the wideband RF amplifier 13 turns on the wideband high-speed RF switch 14.15 corresponding to each channel in the synthesizer 16 by the switching pulse from the control circuit 9, the jamming generator 10.11 is combined with the interference signal (jamming signal) from Then, the demultiplexer 17 sends the output of the combiner 16 to the drop line to the subscriber, and
An upstream signal from the subscriber side is input to the demultiplexer 4 through the combiner 12. In the drawing, reference numeral 2 is a power valve @ (or superimposition) circuit, and 5 is a DC stabilization power supply circuit for converting the AC power obtained from the power separation circuit 2 into a DC stabilization power supply. FIG. 2 provides a detailed explanation of the contents of the jamming generator 10.11. Here, a signal from a voltage a-controlled oscillator (VCO) 20 is divided by a prescaler 21, and this frequency-divided output signal is sent to a programmable divider 2.
Enter 2. Here, P from the control circuit 9 is
The frequency division ratio is changed in time series according to the LL data, and the frequency-divided signal is input to the phase comparator 24. The phase comparator 24 compares the output signal from the reference frequency oscillator 23 with the input signal, and feeds back the difference signal component to the VCO 20 via the low-pass filter 25. In the PLL circuit configured in this manner, a jamming signal having a time-divided frequency corresponding to each channel is periodically output to the frequency converter 27. In this case, the first
Jamming occurred 2! ) PLL data to 10 is VC
The oscillation frequencies generated in time division at O20 are set so that they are arranged sequentially within a period slightly shifted from the TV vertical synchronization. On the other hand, the second jamming generator 11
The PLL data to vC020 is set such that the oscillation frequencies generated in time division in vC020 are randomly aligned every cycle within 1/2, 2/3, or 1/3 of the generation synchronization period in the first jamming generator. It is set. When these signals are expressed as a frequency array, it becomes as shown in FIG. Here, foll~f1nt5 and ro21~fa
The time-division signal as shown in 2n is generated. This jamming signal is input to the frequency converter 27 and converted into a difference component from the carriers fLx and fLz from the local oscillator 26. The output signal from the frequency converter 27 is amplified by a wideband amplifier 28, and is input as a jamming signal to a transmission module 18 corresponding to each terminal via a distributor 29. The output signals of the frequency converter 21 mentioned above are foll~Un and fo2+~fo2nk:
Correspondence L/ r, rj++ ~ fj 1ntr3 yo (
F fj2+ to fj211 (7) are time-division signals. Here, the operation of the jamming generator 10 is expressed on the time axis as shown in FIG. PLL. Data corresponding to each Booyan channel is sent out sequentially during a period Tx (a period slightly shifted from the TV vertical synchronization), and this operation is repeated every period. As a result, the jamming carrier corresponding to each channel has a period T
1 time division signal. The frequency of the carrier fL1 from the local oscillator 26 is set so that the frequency-converted jamming carrier frequency of the jamming generator 10 is 300 to 500K)-1z away from the video carrier frequency of the jammed channel. selected. Similarly, the operation of the jamming generator 10 is expressed on the time axis as shown in FIG. The PLL data is sent out sequentially during the period T2, but is arranged so that the order in which it is sent out every period is random. As a result, the jamming carriers corresponding to each y-yannel are distributed as time-division signals with random periods within a period of 27z or less. Here, the lower period is 1/2.2/3 or 1.2 of the above-mentioned period T1. /3 is selected. and the local oscillator 2 mentioned above.
The period of the carrier rLt from 6 is the jamming generator 1
1 is selected so that the frequency-converted jamming carrier frequency is approximately the same as or several tens of KHz apart from the video carrier frequency of the channel to be jammed. (Effect 1 of the invention As described in detail above, the present invention sets two time-division jamming carries ψ, and one is a time-division signal with a period slightly shifted from the TV vertical synchronization from the video carrier by 30
Since the frequencies are configured to be separated by 0 to 500 KH2, it is possible to have a sufficient interference effect on TV sets with stable vertical synchronization playback, and it is also possible to obtain an interference effect on audio.
In addition, since the time-division signal with other random periods is set to approximately the same frequency as the video carrier, the interference effect will not be impaired even if the TV set is tuned out with good selection characteristics. By incorporating this into the branch line, it is possible to avoid the conventional inconveniences.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a distribution system unit showing one embodiment of the present invention, the second factor is a block diagram showing the internal configuration of a jamming signal generator, and FIG. 3 is a diagram showing time-divided oscillation frequencies. FIG. 4 is a diagram showing each frequency level, and FIGS. 5 and 6 are time charts of each signal. 1... Branch line, 2... Power separation circuit, 3...
Brancher, 4... Brancher, 5... DC stabilized power supply, 6
...Variable resistance annihilator, 1...Distributor, 8...FS
K demodulator, 9...control circuit, 10.11...
- Jamming signal generator, 12... combiner, 13...
・Wideband RF amplifier, 14°15... wideband high-speed RF
Switch, 1G...combiner, 17...brancher, 18
... Sending module, 19... Drop line, 2
0... VCo, 21... Prescaler, 22...
Programmable divider, 23...11 frequency oscillator,
24... Phase comparator, 25... Low pass filter,
26... Local oscillator, 27... Frequency converter, 28
...Broadband amplifier, 29...Distributor. Patent applicant Pioneer Co., Ltd. agent - Patent attorney Ig Ko 4 Same patent attorney Shinshi Murai? 5Q Evening? , 5f3E) 1st friend 1b ( -> 4-15

Claims (1)

[Claims] In a system that scrambles images by adding interference signals to television signals, the distribution system unit that distributes from branch lines to each terminal receives and demodulates control signals from two sets of jamming generators and a center and decodes them. The device is equipped with a control circuit that sends PLL data to each jamming generator according to the received data, and one of the jamming generators uses the PLL data given to the PLL circuit to sequentially transmit PLL data within a period slightly different from the TV vertical synchronization. A voltage controlled oscillator is used to time-divisionally generate an oscillation frequency set to The jamming generator uses a voltage controlled oscillator to generate an oscillation frequency set within a period of 1/2, 2/3, or 1/3 of synchronization slightly shifted from the TV vertical synchronization using PLL data given to the PLL circuit. The frequency generated by the voltage controlled oscillator is generated in a random order every cycle, and the frequency generated by the voltage controlled oscillator is converted by a local oscillator to a frequency that is approximately the same as the TV video carrier frequency or is within several tens of KHz apart, and this is used as an interference signal. A centralized viewing control method in a CATV system characterized by superimposing it on a television signal.