JPH0220198B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention is directed to a TV set targeting a specific number of subscribers.
The present invention relates to a TV signal converter used for broadcasting, such as CATV broadcasting.

[Conventional technology]

The broadcasting method for general TV broadcasting aimed at an unspecified number of recipients is so-called stream broadcasting, but in TV broadcasting aimed at specific subscribers, such as CATV, each subscriber is given a subscriber code (address data). ) and a program contract code (authorization data), and the transmitting side sends out these data and other control signals in addition to the TV signal.
Individually controlling and servicing receivers.

For example, in pay programs (pay broadcasting), the video signal to be sent out is transformed by scrambling processing, and in addition to the descrambled synchronization signal (hereinafter referred to as SYNC signal) superimposed on this signal, there is a function to enable this synchronization signal. Address data and authorization data were sent as separate signals, allowing subscribers to receive them but preventing non-subscribers from receiving them.

In addition, as a parental control service, parental control data is superimposed on the TV signal and sent out, and on the receiving side, if the mode switch connected to the TV signal converter is switched to the parental control mode, the TV program that has a parental contract can be used. There is a service that can make it impossible to receive images. This service is effective when the recipient does not want the child to watch adult programs while the parent is away.The mode switch is set to a key lock type, and the parent carries this key when going out. , others who do not have the key cannot change the mode or receive programs containing parental control data.

In order to receive these controls and services, the receiving side requires a TV signal converter for the CATV broadcast network, and this must be a so-called addressable converter that has addressable functions that can be individually controlled from the transmitting side. . Figure 3 shows a system diagram of a conventional addressable converter.
This will be explained based on the diagram.

The CATV RF signal input from the input terminal 1 is distributed to the first mixer 7 and the FM signal demodulator 2. In addition to the TV signal of each channel, this RF signal includes, for example, in the United States,
Contains an FM signal frequency modulated at 106.5MHz,
The FM signal contains address data, authorization data, etc., and after the FM signal is demodulated by the FM signal demodulator 2, the address data, authorization data, and other data are extracted by the data separation circuit 3. These data are converted into parallel data by a serial-to-parallel conversion circuit 4 and provided to a microprocessor 20 (hereinafter referred to as a microcomputer).

On the other hand, the RF signal distributed to the first mixer 7 is mixed here with a local oscillation signal from the first local oscillator 6 whose oscillation frequency is controlled by the tuning circuit 5, and is mixed with a local oscillator signal of about 700 MHz, for example. The second intermediate frequency is converted into a first intermediate frequency, and further mixed with the local oscillator signal from the second local oscillator 9 in the second mixer 10.
After being converted to the second intermediate frequency of 60 MHz, it is distributed to the descrambler 15 and the AM signal demodulator 11.

The signal demodulated by the AM signal demodulator 11 is sent to the next data separation circuit 12, where a SYNC signal, program code data, parental control data, and other data are extracted. 14, and other data is converted into parallel data by a serial-to-parallel conversion circuit 13 and provided to the microcomputer 20.

In addition to the CPU 22, the microcomputer 20 has an input/output port 21 for data input/output, a RAM 23, and an internal
It consists of a ROM 24, a clock generation circuit 25, and other components, and is connected to an external ROM 26 in which address data assigned to each TV converter is written in order to identify the subscriber.

On the transmitting side, address data and authorization data corresponding to the number of subscribers are sent out sequentially in a time-sharing manner using the FM signal, and the microcomputer 20 operates according to a program written in the internal ROM 24 to The address data inputted from the parallel conversion circuit 4 is compared with the address data of the external ROM 26, and if a match is inputted, the authorization data corresponding to the address is written into the RAM 23.

Authorization data records the subscriber's contract status for pay programs, and if the subscriber operates the channel selection circuit 5 to select a pay program channel, the channel number will be changed to the microcomputer 2.
0, and the program code that is superimposed on that channel is input to the serial-to-parallel converter circuit 1.
3 to the microcomputer 20, the microcomputer 20 refers to this program code and the authorization data written in the RAM 23, and if the program is subscribed to, the descrambler control circuit 14 outputs the descrambler ON signal. It is programmed to output a disk scrambler.
When the ON signal is output, the descrambler control circuit 14
The SYNC signal is sent to the descrambler 15, and the scrambled signal is restored by the descrambler 15 and sent to the RF attenuation switch 16.
The microcomputer 20 is programmed not to output the descrambler ON signal to the descrambler control circuit 14 if the program is not subscribed to, so it is output from the output terminal 19 to the television receiver. The signal that is output to the TV remains scrambled, and although the audio can be heard on the TV, the image cannot be discerned.

Now before we talk about parental controls
The data included in the TV signal will be explained based on FIG. 4. In the figure, 35 is the AM signal demodulated waveform, 36 is the SYNC signal synchronized with each horizontal synchronization signal in the TV signal, and 37 is the program code data, the parental 16 control data and other data
It is encoded in bits, and each
After the SYNC signal 36, bits 1 and 0 are superimposed to indicate the presence and absence of a pulse, respectively.

In FIG. 4, portions where there is no pulse because the bit is 0 are shown by vertical dotted lines for ease of understanding. 39, 40, and 41 are one horizontal synchronization period, one data period, and one vertical synchronization period, respectively,
In the case of NTSC method, each time is 63.5μS,
1mS, 16.7mS.

One bit of the 16 bits is assigned to the parental control data, and when this bit is 1, parental control is possible. To explain the operation of the parental control based on FIG.
You can enable or disable parental control mode by toggling OFF or ON.

The mode switch 18 is connected to the microcomputer 20, and the microcomputer 20 can recognize the ON or OFF state. When mode switch 18 is switched to parental control mode,
If the bit assigned to the parental control data is 1, the microcomputer 20 is programmed to issue a parental control ON signal to turn the RF attenuation switch 16 into an attenuation state.
When the RF attenuation switch 16 enters the attenuation state, the RF signal passing through the RF attenuation switch 16 is attenuated and becomes blocked.

[Problem that the invention attempts to solve]

However, the RF attenuation switch 16 is an attenuation circuit made up of nonlinear elements such as switching diodes, and cannot completely block signals attempting to pass through. Even if the video signal is attenuated relatively lightly, it becomes impossible to distinguish the contents, but the audio signal cannot be identified unless it is attenuated by at least 60 dB, and the circuit would be complicated to attenuate it by as much as 60 dB, making it difficult to realize it easily. Can not.

In addition, in this type of attenuation method, a nonlinear element is inserted into the signal path, which causes signal distortion in the case of strong electric field input or strong input interference. The problem was that it could not be realized.

[Purpose of the invention]

The present invention aims to provide a TV signal converter that can make not only video but also audio indistinguishable with a simple circuit during the parental control.

[Means for solving problems]

In order to solve the above problems regarding parental control, the present invention provides a local oscillation stop circuit that receives a parental control ON signal output from a microcomputer and turns off the power to the local oscillator.

[Effect]

When the conditions for parental control are met, the microcomputer issues a control signal to turn off the power to operate the local oscillator and stop the local oscillator, so the oscillation voltage from the local oscillator is no longer supplied to the mixer. The frequency conversion function of the mixer is lost, making it impossible to obtain the desired output.

〔Example〕

FIG. 1 shows a system diagram of an embodiment of the TV signal converter according to the present invention. 8 in the figure is a local oscillation stop circuit, and its basic circuit is shown in FIG. Second
In the figure, 27 is a control terminal connected to the microcomputer 20, 28 is a power input terminal connected to a -22V power supply, 29 is a power output terminal that supplies power to the second local oscillator 9, 30 and 31 are transistors, 32 and 33 are resistors, respectively. To explain the operation of this circuit, the control terminal 27 is activated by the parental control ON signal from the microcomputer 20.
When a voltage of -5V is applied to the transistor 31, the transistor 31 becomes conductive, and the potential of the point A becomes approximately the same as that of the ground. In this state, the transistor 30 is non-conductive, the -22V voltage applied to the power supply input terminal 28 is not output to the power supply output terminal 29, and the second local oscillator 9
doesn't work. On the other hand, when the voltage applied to the control terminal 27 becomes 0V due to the parental control OFF signal from the microcomputer 20, the transistor 31 becomes non-conductive, and since point A is connected to the power input terminal 28 via the resistor 32, the power supply It becomes approximately equal to -22V applied to the input terminal 28. In this state, the transistor 30 becomes conductive, a voltage of approximately -22V is output to the power output terminal 29, and the second local oscillator 9 operates to supply an oscillation voltage to the second mixer 20. A TV signal converted to a predetermined frequency is obtained.

The rest of the configuration in FIG. 1 is the same as the conventional TV signal converter shown in FIG. 3 except for the RF attenuation switch 16, so the same numbers will be given and the explanation will be omitted.

In this embodiment, for the reason described below, the second local oscillator 9 stops operating for several tens of seconds, and then oscillates for about 20 mS, during which the microcomputer 2
If parental control data is input to 0, the oscillation is stopped again, but if no parental control data is input, the oscillation is continued, which is an intermittent stop method.

That is, if the oscillation operation of the second local oscillator 9 is simply stopped, it will remain stopped unless some kind of recovery operation is performed, and if you want to receive a non-parental control program following a parental control program, the parental control program Even if an RF signal that does not include a parental control signal is input after the end of the program, it still cannot be received. If there is a program you want to watch and you want to watch it from the beginning, it is common practice to turn on the device and set the channel before the program starts. However, there is an inconvenience in that the TV reception remains stopped even though the program start time has passed.

Next, the time during which the second local oscillator 9 is intermittently stopped and activated according to this embodiment will be explained. These times are controlled by the internal clock of the microcomputer 20, and are controlled by the horizontal and vertical synchronization included in the TV signal. It is asynchronous with the signal. Therefore, in order to operate the second local oscillator 9 and obtain the complete data period 40 shown in FIG. 4 at least once, the operating time is the sum of one data period 40 and one vertical synchronization period 41. , that is, it needs to be 17.7 mS or more. In this example, the operating time is approximately 20 mS.
The stop time is selected to be as long as possible to avoid the above-mentioned inconvenience, and is set to several tens of seconds. During the stop time, when a return operation is performed such as switching to another channel by operating the channel selection circuit 5 that cancels the parental control mode by switching the mode switch 18, the second local oscillator 9 starts oscillating.

Note that each circuit operates normally for the aforementioned operating time of about 20 mS, and during that time, theoretically, video and audio are output from the output terminal 19, but because it is a short time, the video may be incomplete and flicker momentarily. Only,
Also, the audio is only a clicking sound and cannot be identified.

〔Effect of the invention〕

When performing parental control, the present invention stops the power supply to the second local oscillator, so both video and audio can be completely cut off during that time, and power is supplied intermittently for short periods of time. As a result, the presence or absence of parental control data can be monitored during that time, and if the data is no longer present, operation is immediately restored and reception is possible. Also, the power supply circuit
Since it is an ON/OFF system, it can be implemented with a simple electronic switch circuit, making it possible to provide an inexpensive TV signal converter.

[Brief explanation of drawings]

Fig. 1 is a system diagram of an embodiment according to the present invention, Fig. 2 is a basic circuit diagram of a local oscillation stop switch, Fig. 3 is a system diagram of a conventional example, and Fig. 4 is a descramble synchronization signal and data bits by CATV. An explanatory diagram is shown. 8... Local oscillation stop circuit, 9... Second local oscillator, 10... Second mixer (frequency conversion circuit),
18...Mode switch, 20...Microprocessor, 12...Data separation circuit.

Claims (1)

[Claims] 1. A frequency conversion circuit that converts the frequency of a received television signal, a local oscillator that supplies a local oscillation signal to the frequency conversion circuit, and a data separation circuit that separates and extracts parental control data superimposed on the television signal. In a TV signal converter equipped with a microprocessor having a control function based on the parental control data and a mode switch, the local oscillator is controlled based on the operation of the mode switch and the parental control data. A TV signal converter characterized by being equipped with a local oscillation stop circuit that stops operation intermittently.