JPH02123887A - Catv terminal equipment - Google Patents

Abstract

PURPOSE:To prevent an output of noise sound from a TV receiver even if the power of the TV receiver is applied by devising the terminal equipment such that an audio signal is not outputted through an audio signal output control circuit provided to an audio signal path when the power supply of the CATV terminal equipment is turned off. CONSTITUTION:When the AC power supply of a TV receiver is not supplied from an AC outlet 21 of the CATV terminal equipment, only the power supply of the TV receiver is supplied when the power of the CATV terminal equipment by a remote controller 26 is interrupted and a comparatively large noise sound is sounded from the TV receiver to give a sense of displeasure to a viewer. Then a mute SW 15 normally closed is provided to the post-stage of an electronic ATT 14 and is opened when the power supply of the CATV terminal equipment is interrupted by using the remote controller 26 to avoid a sudden noise or large sound from being sounded from the TV receiver whose power supply is applied thereby avoiding a sense of displeasure to a viewer.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a CATV terminal device.

(Prior Art) Generally, a CATV terminal device has an AC outlet that is turned on and off by turning the power on and off with a remote control device (remote control device).
By connecting the power outlet of the TV receiver 1 to the AC outlet ACOUT as shown in FIG. There is.

However, as shown in FIG. 5(b), the AC power for the TV receiver 1 is supplied via the AC outlet of the video tape recorder (VTR) 3, or as shown in FIG. In some cases, it may be supplied separately from 2. In particular, the latter connection must be adopted for TV receivers in which memory contents such as channel frequency settings are erased unless the power is turned off using a dedicated remote control device.

In this way, the power supply of the TV receiver is connected to the A of the CATV terminal 2.
It is not necessarily taken from C outlet ACOUT.

As mentioned above, the power supply of the TV receiver 1 is connected to the CATV terminal 2.
If you choose to obtain power from a source other than the AC outlet of the
When the power to the TV terminal 2 is turned off using the dedicated remote control device, the TV receiver l remains powered on until the power is turned off using the dedicated remote control device. Pictures and sounds will be produced. In addition, if two remote control devices are used, one for the CATV terminal and the other for the TV receiver, the remote control devices may be misused, and when the TV receiver is turned off, the
A similar problem occurs when the ATV terminal is turned off and left unattended when the user goes out.

At this time, a specific signal is transmitted to produce a specific image and sound.
It is being considered to output to a V receiver. However, if a normal broadcast signal (video carrier signal, audio carrier signal, etc.) is set as this specific signal, it will be necessary to prepare a dedicated transmission device at the head end to transmit this signal, so it will not be possible to actually broadcast the signal. It is often set to a frequency other than a wave or a carrier frequency of an external command signal.

[Problem to be solved by the invention]

However, if you do this, when the power to the CATV terminal is off and the power to the TV receiver is on, no picture will be displayed but a snow screen will be displayed, and the audio will generate a noise like "zah". This comes to be felt by the viewer as an unpleasant sound.

Therefore, the present invention is designed to prevent the noise from coming from the TV receiver when the power of the CATV terminal is turned off, even if the power of the TV receiver is on, thereby eliminating the viewer's discomfort. Our goal is to provide a CATV terminal device with

[Means to solve the problem]

CATV made by the present invention to solve the above problems
The terminal device includes a converter that converts the frequency of the RF multiplied signal transmitted through the transmission path into an intermediate frequency signal, and a demodulator that demodulates the intermediate frequency signal obtained as the output of the converter and separates it into a video signal and an audio signal. , a modulator that modulates the audio signal and video signal obtained at the output of the demodulator and converts them into a specific channel signal, and an audio signal output provided in an audio signal path between the demodulator and the modulator. The device is characterized by comprising a control circuit and a controller that controls the audio signal output control circuit in response to a power-off operation and prevents the audio signal from being output.

[For production]

In the above configuration, in response to a power-off operation, the controller generates a mute signal that opens a normally open mute switch provided in an audio signal path between the demodulator and the modulator. Therefore, noise is prevented from being output from the TV receiver, and the viewer's discomfort is eliminated.

〔Example〕

Embodiments of the present invention will be described below based on the drawings.

FIG. 1 is a block diagram showing an embodiment of the CATV terminal device according to the present invention. In the same figure, 11 is an input terminal of the CATV terminal device, and the input terminal is connected via a transmission path such as a coaxial cable (not shown). connected to the center as a headend.

12 is a converter, and the converter 12 is 50MH
It is transmitted using the frequency band from z to 550 MHz (
A desired channel is selected from among the multi-channel video signals, and the video signal of the selected channel is frequency-converted to obtain an intermediate frequency signal (IF signal). A demodulator 13 demodulates the IF signal from the converter 12, and the demodulator 13 separates the IF signal into a video signal and an audio signal.

14 is an electronic attenuator (ATT);
14 attenuates the audio signal separated by the demodulator 13 in the relationship shown in FIG. 2 by a voltage corresponding to the volume adjustment level applied to its control input. 15 is a mute switch (SW), and the mute 5W15
When muting the output signal of the electronic ATT 14, the mute signal applied to its control input prevents the audio signal from being supplied to the subsequent stage.

Amplifiers 16a and 16b respectively amplify the video signal from the demodulator 13 and the audio signal that has passed through the mute 5W15.

17 is a modulator, and the modulator 17 is connected to amplifiers 16a, 1
Using the video signal and audio signal amplified by 6b as modulation signals, a carrier signal having a frequency corresponding to an empty channel of the TV receiver is subjected to FM modulation. 18 is a 2 or 3 channel RF modulated by the modulator 17;
This is an output terminal for outputting a double signal to a TV receiver (not shown). 19 is an AC power input terminal 20 and an AC outlet 21
is a relay contact connected between the relay contact 1 and
9 supplies AC power to the equipment connected to the AC outlet 21 when the AC outlet 21 is closed.

22 is a controller constituted by a microcomputer (μmC0M) that operates according to a predetermined program, and the controller 22 controls the above-mentioned ATT14, mu) SV40, modulation based on command signals from the center described above and the remote control device described later. A control signal is generated to control the device 17 and the relay contact 19.

23 is a band pass filter (BPF) connected to the input terminal 11, and the BPF 23 is connected to the FSK (frequency 5 shift) through a transmission cable.
(keying) selectively passes an external command modulated signal transmitted using a modulation method. 24 demodulates the external command modulation signal that has passed through the BPF 23 and outputs the BPS (by
The demodulator 24 converts the command demodulated signal into a command demodulated signal of the phase 5 pace) system, and the command demodulated signal obtained by demodulation by the demodulator 24 is applied to the controller 22. Incidentally, as the external command modulation signal, one having a format as shown in FIG. 3 is used.

Reference numeral 25 denotes a remote control light receiving section, and the remote control light receiving section 25 receives a remote control optical signal from the remote control device 26, converts it into an electrical signal, and applies the converted remote control signal to the controller 22. In response, the controller 22
generates the above control signal based on the above remote control signal,
This is applied to a predetermined controlled object. For example, when a volume adjustment operation is performed using the remote control device 26, the controller 22
applies a voltage corresponding to the adjusted volume level to the ATTl 4 as a control signal. In addition, the remote control device 26
When the power is turned off, the controller 22 generates a control signal related to the relay contact 19 and also generates a mute signal to open the SV 40.

Note that 27 is a channel selection switch connected to the controller 22, and the switch 27 is used to set the carrier frequency used in the modulator 17 to one of a plurality of available channels.

As mentioned above, the IF multiplied signal obtained by frequency conversion by the converter 12 is separated into a video signal and an audio signal in the demodulator 13, and the audio signal is converted into an electronic A
After passing through the TT 14, the audio signal and the video signal whose volume is controlled in the subsequent stage are FM-modulated again in the demodulator 17, and are outputted as an RF multiplied signal to the TV receiver. The volume control in this electronic ATT 14 is realized by controlling the level of the audio signal in a direction that lowers it, taking distortion into account for the convenience of FM modulation in the subsequent stage. Therefore, the volume of the TV receiver should be adjusted to a high volume position in advance, and the volume adjustment should be done exclusively on the CATV.
This will be done using the volume function on the terminal device side. In this case, if the AC power of the TV receiver is not taken from the AC outlet 21 of the CATV terminal device, when the power of the CATV terminal device is turned off by the remote control device 26, only the TV receiver is in the power on state, and the TV receiver is not connected to the TV receiver. A relatively loud noise sound is emitted, causing further annoyance to the viewers.

In this regard, in the embodiment of the present invention, a normally open mute SWI 5 is provided after the electronic ATT 14.
Switch SW15 to the remote control device 26 to power the CATV terminal device.
According to the information regarding when the TV receiver is turned off, even if the TV receiver is turned on, unexpected noises and loud sounds are not emitted from the TV receiver, so that viewers are not made to feel uncomfortable.

Also, at this time, the controller 22 sends a channel control signal for selecting a specific channel to the converter 12 in response to the power off, causing the converter 12 to select a specific channel,
Only the video signal of the selected channel is sent to the TV receiver. Therefore, the image of a specific channel is displayed on the TV receiver without sound.

In the above configuration, the operation of the CATV terminal device will be described below with reference to the flowchart of FIG. 4 showing the work performed by μmC0M constituting the controller 22 according to a predetermined program. In the figure, in the first step S1, it is determined whether or not a remote control optical signal from the remote control device 26 is input via the remote control light receiving section 25, and if a remote control signal is input and the determination in step S1 is YES, Proceeding to step S2, if no remote control signal is input and the determination is No, the process proceeds to another step (not shown) for performing another task.

In step S2', it is determined whether one remote control signal inputted from the remote control device 26 is due to a key operation to turn off the power. In step S3, an off control signal is output to open the relay contact 19, and after step S3 is executed, the process proceeds to step S4. In step S4, a mute signal for opening the mute 5W15 is output, and the process returns to the unillustrated step of restoring the mute signal.

Note that if the determination in step S2 is NO, that is, the power off key has not been operated on the remote control device 26, steps S3 and S4 are skipped and the process returns to the original step (not shown).

With the above operation, when the power of the CATV terminal device is turned off by the remote control device 26, the mute 5W15 is opened, so that no audio signal appears at the output of the modulator 17.

Therefore, if the power supply of the TV receiver is A of the CATV terminal device,
Even if it is taken separately rather than from the C outlet 21, unexpected noise or loud audio will not be output from the TV receiver, and the viewers will not be annoyed.

〔effect〕

As explained above, according to the present invention, when the power of the CATV terminal device is turned off, the audio signal is no longer output through the audio signal output control circuit provided in the audio signal path. Even if 1. Noise sounds are not output from the TV receiver, and the viewer's discomfort is eliminated.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing an embodiment of the CATV terminal device according to the present invention, Fig. 1 is a characteristic diagram showing the control characteristics of the electronic ATT in Fig. 1, and Fig. 3 is a transmission from the center to the CATV terminal device. An explanatory diagram showing the format of the external command signal to be sent.
FIG. 5 is an explanatory diagram showing the power supply relationship between the CATV terminal device and the TV receiver. 12...Converter, 13...Demodulator, 15...
Mute switch, 17...Modulator, 22...Controller.

Claims (1)

[Claims] A converter that converts the frequency of an RF signal transmitted through a transmission line into an intermediate frequency signal, and a demodulator that demodulates the intermediate frequency signal obtained from the output of the converter and separates it into a video signal and an audio signal. a modulator that modulates the audio and video signals obtained at the output of the demodulator and converts them into specific channel signals; and an audio signal path provided in the audio signal path between the demodulator and the modulator. A CATV terminal device comprising: a signal output control circuit; and a controller that controls the audio signal output control circuit in response to a power-off operation to prevent audio signals from being output.