JPS61230485A - Converter for catv - Google Patents

Abstract

PURPOSE:To control not to reproduce a sound signal in a broadcasting channel that is not contracted by mixing the sound signal component of a special channel in which the frequency of a sound FM carrier is converted, in a state that it is sufficiently larger than the level of the sound signal component in a TV signal that is not contracted, with the sound signal component in the TV signal that is not contacted. CONSTITUTION:The frequency of the sound FM carrier in the TV signal is converted to the same one in the TV signal that is not contracted and inputted to a main circuit A. The sound signal component in the special channel at a sub-circuit B side, the frequency of which is the same with that of the sound FM carrier, and the sound signal component at the main circuit A side that is not contracted are mixed. At such a time, so that the level of the sound signal component at the sub-circuit B side is not passed through many circuit apparatus including a variolosser 11, etc., not like at the main circuit A side, it is maintained at a sufficient higher level comparing to the level of the sound signal component at the main circuit A side. Therefore, the sound signal in a channel that is not contracted is masked with the sound signal in the special channel and is not reproduced from a TV receiver.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a CATV converter for receiving pay programs, and in particular to a converter that cannot receive audio signals of programs outside the reception contract. be.

(Prior Art) Usually, the video signal components of a TV signal in CATV are scrambled by, for example, a synchronization suppression method, and measures are taken to prevent a normal television receiver from viewing the signal.

Then, subscribers will be required to install a converter.
Tag data for synchronization signal reproduction is transmitted from the transmitting side within the broadcast band, and a converter on the receiving side reproduces the synchronization signal into the video signal component based on this tag data.
Even V receivers can receive the contract programs.

FIG. 2 is a diagram showing an example of such a conventional CATV converter. In the figure, 1 is a TV signal input terminal, 3 is a low-pass filter, 4 is a first mixer, 5 is a first oscillator with variable oscillation frequency, 6 is a band-pass filter for selecting a desired broadcast channel, and 7 is a first mixer. 2 is a mixer, 8 is a second oscillator with a fixed oscillation frequency, 9 is a band pass filter, 10 is a splitter, 11 is a varioscillator, 12 is a data receiver, and 14 is a TV signal output terminal.

Then, when a TV signal group including an audio signal component and a scrambled video signal component and tag data are input as a composite signal within a predetermined RF band from the input terminal 1, this composite signal passes through a low-pass filter 3 and then After the frequency is suitably converted by the first mixer 4 section, a desired broadcast channel is selected via the band pass filter 6.

The selected TV signal is frequency-converted by the second mixer 7 to the frequency of a predetermined vacant channel preset in the subscriber's receiver (not shown). This frequency-converted TV signal (synthesized signal) passes through a bandpass filter 9 and is divided into two by a splitter 10, one of which is applied to a data receiver 12 and the other to a variosser 11. The data receiver 12 extracts tag data from the composite signal, and this tag data becomes a drive signal for reproducing the synchronization signal and inputs it to the variosser 11.
The video signal component in the V signal is descrambled, the synchronization signal is reproduced in the video signal component, and the terminal 1
A regular TV signal is output from 4, which is input to the subscriber's receiver to reproduce the images and audio of the desired program.

If the broadcast channel selected by the first mixer 4 and bandpass filter 6 is a non-contracted channel, the data receiver 12 is provided with means that prevents it from reproducing the tag data. Therefore, images of broadcast channels outside the contract cannot be played back on the TV receiver of this subscriber.

(Problem to be solved by the invention) However, since the audio signal component in the TV signal is not subjected to any scrambling processing, even if the broadcast channel is not under contract, only the audio signal is sent from the TV receiver via a converter. There was a problem that the files were played back normally.

The purpose of this invention was to address the problems of conventional CATV converters, and to provide a CATV converter that prevents audio signals from being played on broadcast channels that are not under contract. be.

(Means for solving the problem) In order to achieve this purpose, the CAT related to this invention
The converter for V is the main circuit that receives the TV signal of the selected channel, and the TV signal of special channels such as program guide.
means for receiving the signal and converting the frequency of the audio FM carrier wave of the special channel into the same frequency as the frequency of the audio FM carrier wave in the TV signal outside the reception contract when the TV signal outside the reception contract is input to the main circuit; and a sub-circuit comprising: a sub-circuit that transmits the audio signal component of the special channel whose frequency has been converted, the level of which is sufficiently higher than the level of the audio signal component in the TV signal outside the reception contract; TV
and means for mixing the audio signal component in the signal.

(Function) The audio signal component on the special channel whose FM carrier frequency is the same and the audio signal component on the channel outside the reception contract are mixed with the level of the former audio signal component being sufficiently high. Audio from channels outside the reception contract is masked with audio from special channels and is not played back.

(Example) An example of the present invention will be described below based on FIG. 1. In FIG. 1, the same or equivalent components as those in FIG. 2 are designated by the same reference numerals, and redundant explanation will be omitted.

First, to explain the configuration, in this invention, in contrast to the main circuit A which receives the TV signal of the broadcasting channel to which the user has subscribed, which has almost the same configuration as that shown in FIG. 2, the sub-circuit B has the following configuration. are arranged side by side. That is, a tap 2 is provided between the input terminal 1 and the low-pass filter 3, and a line branched at this tap 2 is connected to a band-pass filter 15 for selecting a special channel such as a program guide, and a third mixer 1B. , and a bandpass filter 18 are connected in sequence.

On the other hand, a channel mixer 13 is disposed between the parilotzer 11 and the output terminal 14, and the bandpass filter 18
An output terminal of the channel mixer 13 is connected to one input terminal of the channel mixer 13. 17 is a local oscillator for the third mixer 16, and a control signal line from the data receiver 12 is connected to this local oscillator 17.

The bandpass filter 15 constitutes means for selecting special channels such as program guide, and the third mixer 16
And in the local oscillator 11, when a TV signal of a broadcasting channel other than the reception contract is input to the main circuit A, the frequency of the audio FM carrier wave in the TV signal of the special channel is input to the main circuit A. A means for converting the frequency to the same frequency as the carrier wave is configured, and the audio signal component in a special channel such as a program guide where the frequency of the audio FM carrier wave is made the same by the channel mixer 13, and the audio signal component in a broadcast channel outside the reception contract. A means for mixing the two is constituted. A subcircuit B is constituted by the above-mentioned special channel selection means, means for converting the frequency of the audio FM carrier wave into the same frequency, and the like.

Next, the action will be explained.

First, when the TV signal of the broadcasting channel that is subscribed to among the TV signal group inputted from the input terminal 1 is selected by the main circuit A, in the same manner as explained in the case in FIG. 2 above,
A regular TV signal in which a synchronization signal is reproduced in the video signal component is led from the output terminal 14 to the TV receiver, and normal image and audio reproduction is performed. At this time, data receiver 1
The local oscillator 17 is held in an oscillation stopped state by the control signal from 2, and no channel selection operation is performed in the subcircuit B.

Next, when the main circuit A selects a TV signal from a broadcasting channel that is not included in the reception contract, the video signal component in the TV signal is scrambled as described above, so the image is not reproduced on the TV receiver. . At this time, since no oscillation stop signal is input from the data receiver 12 to the local oscillator 17, the local oscillator 17 and the third mixer 16 are in a normal operating state. In this state, the bandpass filter 15 selects a TV signal of a special channel such as a program guide from the TV signal group input through the tap 2, and the third mixer 16 selects the TV signal of a special channel such as a program guide. The frequency of the carrier wave is converted to the same frequency as the frequency of the audio FM carrier wave in the TV signal input to the main circuit A, which is not under the reception contract. Then, the audio signal component in the special channel on the sub-circuit B side, in which the frequency of the audio FM carrier wave is made the same, and the audio signal component on the main circuit A side, which is outside the reception contract, are mixed by the channel mixer 13. At this time, the level of the audio signal component on the side of the subcircuit B is sufficiently high compared to the level of the audio signal component on the side of the main circuit A, since it does not pass through many circuit devices including the parilotzer 11 as on the side of the main circuit A ( The audio signal component level is maintained at a level of about 6 dB or more, and the channel mixer 13 mixes these two audio signals of large and small audio signal component levels.

By the way, when two FM modulated signals with the same carrier frequency and FM modulated with different modulated signals (audio signals) are simultaneously received by an FM receiver, the signal level of one modulated signal will be the same as that of the other modulated signal. It is known that when the level is sufficiently large (difference of about 6 dB or more) compared to the above, a masking phenomenon occurs in which only signals on the higher level side are demodulated.

In a similar phenomenon, in the case of the present invention, audio signal components having the same carrier frequency and the level of one audio signal component being sufficiently higher than the level of the other audio signal component are mixed, and this is transmitted to the TV receiver. Therefore, the audio signal of the channel outside the reception contract is masked with the audio signal of the special channel and is not reproduced from the TV receiver.

In order to increase the level of the audio signal component of the channels outside the reception contract to a desired level, suitable amplification means may be provided in the subcircuit.

(Effects of the Invention) As detailed above, according to the present invention, the audio signal component in a special channel such as a program guide where the frequency of the FM carrier wave is the same and the audio signal component in a channel outside the reception contract are the same. Since the latter level is sufficiently higher than the latter level, the audio signal of the channel outside the reception contract is masked with the audio signal of the special channel and is not reproduced from the TV receiver.

[Brief explanation of the drawing]

FIG. 1 is a block circuit diagram showing an embodiment of a CATV converter according to the present invention, and FIG. 2 is a block circuit diagram showing a conventional CATV converter. A: Main circuit, B: 11 circuits, 1: TV signal input terminal, 4: First mixer, 5: Frequency variable oscillator, 12: Data receiver, 13: Channel mixer, 1
4: Output terminal, 15: Bandpass filter, 16:
Third mixer, 17: Local oscillator.

Claims (1)

[Claims] (1) A main circuit that receives the TV signal of the selected channel and a TV signal of a special channel such as a program guide, and transmits the frequency of the audio FM carrier wave of the special channel to the main circuit for TV signals that are not under the reception contract. a sub-circuit that converts the audio signal component of the special channel whose frequency has been converted to the same frequency as the frequency of the audio FM carrier wave in the TV signal outside the reception contract when the frequency is input, and converts the audio signal component of the special channel whose level is A converter for CATV, characterized in that it is equipped with means for mixing an audio signal component in a TV signal outside the reception contract at a level sufficiently higher than the level of the audio signal component in the TV signal outside the reception contract. .