JPH0369461B2 - - Google Patents

Description

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

The present invention relates to a terminal device for a CATV system in which an audio signal is transmitted through a channel different from a video signal for one source in the CATV system, and the terminal device side can reproduce FM stereo broadcasting.

[Conventional technology]

Generally speaking, in a CATV system where the audio is monaural,
Stereo broadcasting is carried out using so-called simulcast, which transmits audio signals for FM stereo on a different channel from the video and audio signals for television. The center side of such a CATV system has the configuration shown in FIG. 1, for example. In other words, the TV signal from the video/audio source 1 such as a VTR or video disc is sent to the IF modulator 2 and the IF
When outputted to the channel up converter 4 via the scramble encoder 3, it is combined with other channel signals and sent out to the line. On the other hand, when audio signals for performing a stereo broadcast service on the same source are outputted to an up converter 7 via a stereo encoder 5 and an FM audio modulator 6 in addition to the monaural system described above, they are converted into other channel signals. The signals are combined and sent over the line. FIG. 2 shows an example of a terminal device connected to the line from the center side in FIG. The signal is output to the TV set 9 via the CATV terminal 8 equipped with a decoder 14. The other of the demultiplexed signals is output to the speaker 12 via the stereo FM tuner 10 and audio amplifier 11 of the audio device. Then, on the center side shown in Figure 1,
The video signal and audio signal (monaural) from the video/audio source 1 are modulated by the IF modulator 2,
After converting into video IF signal and audio IF signal, video IF
The signal is scrambled by an IF scramble encoder 3. On the other hand, decoding information for descrambling the video is multiplexed onto the audio IF signal. Apart from this, video and
An audio stereo signal from an audio source 1 is converted into an IF signal after passing through a stereo encoder 5 and an FM audio modulator 6. On the other hand, on the terminal device side shown in Figure 2,
When a signal is received from the center via the line, it is separated into a TV frequency band and an FM broadcast band, the former being supplied to the CATV terminal 8 side, and the latter being supplied to the audio equipment side. When the viewer operates the CATV terminal 8 to watch Hch, for example, the converter 13 tunes Hch. The tuned signal is descrambled by the scramble decoder 14 and then output to the TV set 9 side. As a result, the TV set 9 displays images based on the descrambled signal. At this time, monaural audio is output from the TV set 9. Here, if the viewer wishes to broadcast the same video in stereo, for example, if the stereo broadcast frequency for this video is 84MHz, then
When the FM tuner 10 tunes 84MHz, a stereo service can be received through the speaker 12.

[Problem to be solved by the invention]

However, in the conventional CATV system described above, when receiving a stereo broadcast service on another channel, it is necessary to change the FM tuning every time the channel of the CATV terminal 8 is changed. In such a case, the viewer has to perform tuning by manual operation, which has the disadvantage that the operation is very complicated. The present invention has been made in response to these circumstances, and is a CATV system that can easily perform stereo broadcast tuning operations on the terminal device side.
The purpose is to provide a terminal device for the system.

[Means to solve the problem]

In order to achieve the above object, the present invention provides a terminal device for a CATV system that selects a first TV channel sent out from a center and outputs it to a TV set as a predetermined second TV channel. an externally settable FM tuning means; a switching means for selecting one of the first and second FM signals and supplying the selected FM signal to the FM tuning means; and the first TV channel multiplexed on the first TV channel. FM frequency in the first FM signal simulcast with the TV channel of
comprising data demodulation determination means for demodulating and determining FM broadcast frequency data and controlling the switching means;
The second FM signal is supplied from the output of the second TV channel, the tuning means has a function of tuning according to the FM broadcast frequency data, and the switching means has a function of tuning according to the FM broadcast frequency data, and the switching means has a function of tuning according to the FM broadcast frequency data. selecting the second FM signal when the FM broadcast frequency data is equal to the audio frequency of the second TV channel, and the FM broadcast frequency data is different from the audio frequency of the second TV channel; The present invention is characterized in that it has a function of selecting the first FM signal when the first FM signal is selected.

[Effect]

In the terminal device of the CATV system of the present invention, the FM
The tuning means performs FM tuning based on the data demodulation result by the data demodulation determining means, and the switching means selects the FM stereo broadcast to be simultaneously broadcast, if any, based on the determination result of the data demodulation determining means. Select by switching the TV audio (monaural). Therefore, FM tuning can be performed automatically each time a channel is changed on the terminal device side, and monaural broadcasting can also be played back.

【Example】

Hereinafter, details of embodiments of the present invention will be described based on the drawings. In the figures described below, the configuration on the center side is the same as that shown in FIG. 1. Also, in the diagrams described below,
Components common to those in FIG. 2 are given the same reference numerals and redundant explanations will be omitted. FIG. 3 shows an embodiment of the terminal device of the CATV system of the present invention, which is equipped with a CATV terminal 15. In FIG. Here, in the CATV terminal 15,
It is equipped with the converter 13 and scramble decoder 14 shown in FIG. 2, and is also equipped with an output terminal (not shown) for outputting data to the outside, and the data is output from the controller. . Note that the converter 13 and scramble decoder 14 are both omitted from illustration in FIG. On the other hand, on the FM stereo device side, an FM converter 16 is installed upstream of the FM tuner 10. The FM converter 16 includes a converter 17 that uses a double converter method and an RF relay circuit 20 that switches input paths. Note that these converter 17 and RF relay circuit 2
0 is equipped with an input port (not shown), and is adapted to perform a predetermined operation based on a control signal from the above-mentioned controller. The terminal device of the CATV system having such a configuration performs the following operations. In the following explanation, it is assumed that, for example, Hch and Bch involve stereo broadcasting with simultaneous FM broadcasting, and Fch is monaural broadcasting, that is, there is no simultaneous FM broadcasting and only TV audio. Also, the FM broadcast frequency corresponding to Hch is 84MHz, and that of Bch is
Assume that it is 83MHz. Note that these frequencies are set to be different from the audio frequency of a predetermined TV channel to be output to the TV set 9. First, on the center side, the IF scramble encoder 3 multiplexes scramble decode information and data indicating the stereo broadcast frequency onto the audio signal on the Hch and Bch. Then, when the CATV terminal 15 receives Hch of the signal from the center side via the line, Hch
After the data multiplexed in the scramble decoder 14 is decoded, the data is sent to the controller. The controller outputs a control signal to the converter 17 from the decoded signal to instruct the stereo broadcast frequency of 84 MHz. As a result, the converter 17 performs a tuning operation of 84 MHz, converts this into a constant output frequency, and supplies the output frequency to the stereo FM tuner 10.
Thereby, by performing a tuning operation of the output frequency on the stereo FM tuner 10 side, a stereo broadcast service can be received. Furthermore, the controller determines that stereo broadcasting is present when the information is different from the audio frequency in a predetermined TV channel to be output to TV set 9 based on the decoded information of the Hch stereo broadcast frequency data. and outputs a control signal to receive the stereo broadcast to the RF relay circuit 20. As a result, the RF relay circuit 20 is switched to the A terminal side. Next, a case where the TV band channel is changed from Hch to Bch will be explained. First, since the Bch audio signal is multiplexed with data indicating 83MHz in addition to scramble decoding information, the stereo service corresponding to Bch can be received in the same manner by the operation of each component described above. Next, when the TV band channel is changed from Bch to Fch, the Fch audio signal will have
In addition to scramble decoding information, TV set 9
Data indicating the audio frequency itself on a predetermined TV channel to be output to is multiplexed. Therefore, the controller determines that there is no stereo broadcast, switches the RF relay circuit 20 to the B terminal side, and at the same time tunes the converter 17 to that frequency. This allows you to receive the same audio as the TV output audio signal, that is, a monaural signal.
It can be reproduced through the speakers 12 on the FM stereo device side. In this manner, in this embodiment, FM tuning is automatically performed each time the channel of the CATV terminal 15 is changed, so that the drawback of the extremely complicated operation in the past can be overcome. Furthermore, in the case of monaural broadcasting, the RF relay circuit 20 is automatically switched to the B terminal side, so that the monaural broadcasting can also be listened to through the speaker 12 on the FM stereo device side. In this embodiment, as shown in FIG. 3, a case has been described in which an FM converter 16 that can be externally controlled is provided upstream of the FM tuner 10, but this is not limited to this example.
As shown in the figure, the stereo FM tuner 10 may be replaced with an FM tuner 19 that can be externally controlled. Further, in this embodiment, a case has been described in which stereo broadcast frequency data is multiplexed with an audio signal and sent from the center side, but the example is not limited to this example.
A correspondence table may be provided in the internal ROM of the CATV terminal 15, and when a TV channel is selected, the corresponding stereo broadcast frequency information may be given to the FM converter or FM tuner for control. Furthermore, using a data channel that transmits data from the center side, stereo broadcast frequency data is sent to the CATV terminal side, the data is stored in the internal RAM of the CATV terminal side, and a tuning operation is performed based on this data. Good too.

[Effects of the Invention] As explained above, according to the terminal device of the CATV system of the present invention, FM tuning is automatically performed every time a channel is changed on the terminal device side. Tuning operations for stereo broadcasts can be easily performed, and monaural broadcasts can also be played back.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an example of the configuration on the center side in a conventional CATV system, and FIG. 2 is a block diagram showing an example of the configuration on the terminal device side.
FIG. 3 is a block diagram showing the configuration of the terminal device according to one embodiment of the terminal device of the CATV system of the present invention, and FIG. 4 is a block diagram showing another embodiment in which the configuration is changed. 1...Video/audio source, 2...IF modulator,
3...IF scramble encoder, 4...Channel up converter, 5...Stereo encoder, 6...FM audio modulator, 7...Up converter, 8...CATV terminal, 9...TV set,
10... Stereo FM tuner, 11... Audio amplifier, 12... Speaker, 13... Converter, 14... Scramble decoder, 15...
CATV terminal, 16...FM converter, 17...
Converter, 18...Stereo FM tuner, 2
0...RF relay circuit.

Claims (1)

[Claims] 1. A first TV channel sent from a center is selected and set as a predetermined second TV channel.
In a terminal device of a CATV system outputting to a TV set, an FM tuning means whose tuning frequency can be set externally, and one of the first and second FM signals is selected,
switching means for supplying to the FM tuning means; demodulating FM broadcast frequency data indicating an FM frequency in the first FM signal that is multiplexed on the first TV channel and broadcast simultaneously with the first TV channel; and data demodulation determining means for determining and controlling the switching means, wherein the second FM signal is supplied from the output of the second TV channel, and the tuning means is configured to determine the frequency of the FM broadcast according to the FM broadcast frequency data. The switching means is configured to tune the FM broadcast frequency data to the second frequency according to the control of the data demodulation determining means.
has a function of selecting the second FM signal when the audio frequency is equal to the audio frequency of the TV channel, and selecting the first FM signal when the FM broadcast frequency data is different from the audio frequency of the second TV channel. A CATV system terminal device featuring: