JPS6363152B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a CATV system that connects a center and a terminal device with a cable and allows two-way data communication, and in particular, a CATV system that can prevent unauthorized viewing of programs on the terminal device side. The present invention relates to an eavesdropping prevention device in a system.

First, an overview of the CATV system will be explained with reference to FIG.

Figure 1 shows the entire CATV system. In this system, one center 1 has a terminal device 28 that serves tens of thousands of households 2, and the center 1 and the terminal devices 28 of each household 2 are connected by a coaxial cable. A trunk cable 3 is drawn out from the center 1.
A trunk amplifier 4 and a branch 5 are provided at predetermined locations on the trunk cable 3. A plurality of branch cables 6 are drawn out from this branch 5, and each branch cable 6 has an extension amplifier 7 and a tap-off 8 at a predetermined location.
is provided. From each tap-off 8, the ends of a plurality of branch cables 9 are led into each home 2, respectively. The terminal device 28 in each home 2 is composed of a main box 10, a television receiver 11, and a control box 12.The end of the branch cable 9 is connected to the main box 10, and the television receiver 11 and control box 12 are Each is connected to the main box 10. In other words, the center 1 and the terminal devices 28 of each home 2 are segmented and connected in a Christmas tree shape.

A receiving antenna 13 is erected outside the center 1, and the receiving antenna 13 is connected to a demodulator 15 in a source group 14. This source group 14 includes a video disc player 16,
There are a video tape recorder 17, a studio 18, etc. The modulation sending section 19 that receives signals from the source group 14 consists of two types of systems: one system includes an IF modulation circuit 20, a scramble circuit 21, and an up-converter circuit 22, and the other system includes an IF modulation circuit 23 and an up-converter circuit 24. The outputs of the up converter circuits 22 and 24 are connected to the trunk cable 3, respectively. Further, a data transmitter/receiver 25 for communicating with each main box 10 is connected to the trunk cable 3, and a computer 26 is connected to the data transmitter/receiver 25. A device 27 is connected.

Next, the operation of this CATV system will be explained.
By turning on the television receiver 11 and operating the control box 12 to select a desired channel, the main box 10 converts the frequency of the channel to be received into an empty channel that is not on air. supply to. The types of channels that can be selected in the control box 12 can be divided into groups such as (A) retransmission that receives TV waves as they are, (B) independent programs, and (C) paid programs, and each group has several channels. There are about 20 to 30 choices in total.

(A) Retransmission The television waves received by the reception antenna 13 are demodulated once by the demodulator 15 and output to the modulation transmitter 19. Then, it is modulated by the IF modulation circuit 23, and the modulated signal is increased to a specific frequency by the up converter circuit 24. This modulated signal positioned on a specific channel is transmitted to the trunk cable 3, the branch cable 6,
The signal is transmitted to the home 2 via the branch cable 9 and received by the television receiver 11 via the terminal device 28 .

(B) Independent programs Weather forecasts, news programs, etc., recorded programs by the video display player 16 and video tape recorder 17, and live programs produced in the studio 18 are modulated by the IF modulation circuit 23 and the up converter circuit 24. At the same time, the frequency is converted into a specific channel and transmitted to the trunk cable 3. This program is free of charge regardless of the number of times it is watched or the time, and each household 2 can watch it for a basic monthly fee.

(C) Paid programs These include new movies and specific programs, such as recorded programs by the video disc player 16 and video tape recorder 17, and live programs produced in the studio 18, which are modulated by the IF modulation circuit 20 and scrambled by the scrambling circuit. 21, a specific synchronization signal is added to the image signal so that it does not become a normal image even if the image is received as is. Next, the up converter circuit 22 increases the frequency to the frequency of a specific channel and sends it to the main cable 3. When each household 2 wants to receive this pay program, the signal sent in the main box 10 is demodulated into a normal image signal and transmitted to the television receiver 11, so that it can be viewed on a normal screen. When this pay program is received, a preset fee is calculated and the monthly basic usage fee plus the special usage fee is charged.

The center 1 is connected to the terminal device 28 of each home 2 by a coaxial cable, but unless you know which home 2 is receiving which channel at a particular time, it is difficult to distinguish between paid programs and free programs. ,
Fair operation of the CATV system cannot be expected.
For this purpose, the data transmitter/receiver 25 outputs a search signal at regular intervals, calls the main box 10 of each terminal device 28 with its individual address number, and determines which channel is being received during the search. We perform so-called polling to ask if there are any. Therefore, the main box 10 outputs a response indicating which channel is being received at that time, and sends it to the data transmitter/receiver 25. The data received by the data transceiver 25 is processed by a computer 26 and displayed or printed by a peripheral device 27. Since this polling is performed at regular intervals (every few seconds to several tens of seconds), the audience rating etc. can be immediately compiled. In addition, some programs involve viewer participation, and the viewer can respond to questions in the program by operating the control box 12 while watching the television receiver 11, and the content of the response (data) is It is sent to center 1 by a coaxial cable.

In this way, data communication can be performed in both directions between the center 1 and the terminal device 28.
The center 1 cannot operate the system unless it is constantly aware of the operating status of the terminal devices 28. For example, even if a pay program is being viewed illegally, if the center 1 cannot prevent such fraudulent activity, it will be impossible to accurately collect fees, and system operation will not be maintained. Therefore, the act of surreptitious viewing using illegal means must be prevented in the CATV system. Conventionally,
As mentioned above, the video signal and downlink data signal are always sent from the center 1 to the terminal device 28, and the terminal device 28 responds to the center 1 as an uplink data signal indicating which channel is being viewed, and this uplink data signal The operation of each terminal device 28 was grasped by the following. However, if the reception of the operation status search signal included in the downlink data signal is interfered with by some means, or the transmission of the uplink data signal that responds to which channel is being received, the terminal at center 1 It became impossible to grasp the operating status of the device 28, and it became impossible to prevent eavesdropping.

In view of the above-mentioned drawbacks, the present invention provides a means for determining whether or not a specific signal for searching the operating status is input into the terminal device, and stops viewing by the terminal device when this specific signal is interfered with. , this can prevent eavesdropping.
The present invention provides a device to prevent eavesdropping in a CATV system.

An embodiment of the present invention will be described below with reference to FIG.

The branch cable 9 is connected to a channel converter 31 via a branch 30 within the main box 10, and the output of the channel converter 31 is connected to a television receiver 11. A receiving section 32 for receiving a downstream data signal is connected to the branching device 30, and a clock detecting section 3 is connected to the receiving section 32.
A timer section 34 is connected to the clock detection section 33, and a tuning signal generation section 35 is connected to the timer section 34. The tuning signal generator 35 is connected to the control box 12, and the output of the tuning signal generator 35 is connected to the channel converter 3.
It is connected to 1.

Next, the operation of this embodiment will be explained.

An operating status search signal is constantly sent from the center 1 to the terminal device 28 at a specific frequency, and this signal includes a clock. Therefore, when the main box 10 is operating properly, the receiving section 32 receives this specific signal at its frequency, and the clock detecting section 33 detects the clock included in the operating status detection signal. Therefore, no signal is output to the timer section 34 in a state where it is determined that this specific signal is being received normally. Therefore, the tuning signal generator 35 is controlled by the control box 12 to output a tuning signal corresponding to the selected channel, and causes the channel converter 31 to convert the frequency of the selected channel to a specific channel for TV reception. You can view your favorite program by outputting it to the computer 11.

Here, if the subscriber uses some means to prevent the terminal device 28 from receiving only the downlink data signal in order to perform eavesdropping, the receiving section 32 will not be able to receive the frequency of that specific signal, and this will cause the clock to be detected. The section 33 detects the absence of the clock and transmits its output to the timer section 34. Timer section 34
Then, when the detection signal from the clock detection section 33 continues for several minutes, an operation stop signal is output to the tuning signal generation section 35, and the tuning signal generation section 3
The tuning signal from No. 5 is forcibly changed to a preset channel (an empty channel or a free program channel) to prevent eavesdropping.
At this time, since the stop signal from the timer unit 34 is given priority over the selection signal from the control box 12, channel selection is impossible no matter how the control box 12 is operated. In addition, the timer section 34 is set to have a time loss of several minutes, but this means that if the computer 26 or data transmitter/receiver 25 in the center 1 fails and the carrier wave of a specific frequency or clock cannot be transmitted, the clock can be stolen immediately. This is to prevent it from being judged as a visual act, and if a specific signal is sent out from the spare equipment in Center 1 within these few minutes, the terminal device 28 will continue to broadcast the program regardless of the failure on the Center 1 side. can be viewed.

Since the present invention is configured as described above, it is possible to prevent the act of eavesdropping on the program by illegal means by controlling the terminal device, and if the act of eavesdropping is performed, the program cannot be eavesdropped on the terminal device. By eliminating this, fraudsters will be warned, and the CATV system will operate more smoothly.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing an outline of a CATV system according to the present invention, and FIG. 2 is a block diagram showing the configuration of a terminal device. 1...Center, 28...Terminal device.

Claims (1)

[Claims] 1. A cable connects the center and a large number of terminal devices, and the center sends an operation status search signal as a video signal and a downlink data signal to the terminal device, and the terminal device sends the operation status search signal to the center. It sends out an uplink data signal that indicates the channel being viewed, and communicates between the center and the terminal devices, allowing the center to understand the operation of each terminal device.
The terminal device is a CATV, and the terminal device includes a detection means for detecting that an operating status search signal is normally received among the signals sent from the center to the terminal device, and an operating status search signal is detected by the detection means. 1. An eavesdropping prevention device for a CATV system, comprising a stop means for forcibly stopping the image receiving operation of a television receiver when it is determined that a signal is not being received normally.