JPH0794986A - Muting device - Google Patents

Abstract

PURPOSE:To pass only a required television broadcasting signal and to interrupt other signals. CONSTITUTION:A video/sound intermediate frequency signal from a tuner 54 is directly inputted to a muting circuit 74 through an amplification part 60, an SAW filter 62, an AGC amplification part 64, and a change-over swtich 72 as an example. When an output signal from an amplification part 68 which is obtained by amplifying the output signal of the amplification part 64 exceeds a prescribed level, an intermediate frequency level detecting part 102 supplies an H level output signal to an AND circuit 100. At the time of detecting a synchronizing signal from a base band video signal outputted from a video terminal 58, a synchronism detecting part 104 supplies an H level output signal to the AND circuit 100. Thereby only when the intermediate frequency signal is more than the prescribed level and includes the synchronizing signal, the AND circuit 100 suplies the H level signal to a muting circuit 92 to pass the inputted intermediate frequency signal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mute device for blocking or passing an input signal according to a control signal.

[0002]

2. Description of the Related Art A mute device is used in various devices, but is sometimes used in a channel processor in a head end device of a joint hearing device as shown in FIG.

That is, a television broadcast signal from a broadcast station received by a receiving antenna (not shown) is supplied to the tuner 4 via the input terminal 2. Tuner 4
Selects a desired one of the television broadcast signals, outputs the baseband audio signal to the audio output terminal 6 and the baseband video signal to the video output terminal 8, and converts the frequency of the television broadcast signal. The output intermediate frequency signal is output.

The intermediate frequency signal is amplified by the amplifying section 10 and then supplied to the SAW filter 14 from the output side of the 1-branching device 12. The SAW filter 14 extracts a video intermediate frequency signal from the intermediate frequency signals. The extracted video intermediate frequency signal is amplified by the amplifier 16 and
It is supplied to the level adjuster 20 via the output side of the branching device 18, adjusted to a desired level by this, and then supplied to the combiner 22.

On the other hand, the intermediate frequency signal branched to the branch output side of the 1-branching device 12 is supplied to the SAW filter 24. The SAW filter 24 extracts an audio intermediate frequency signal from this intermediate frequency signal. This audio intermediate frequency signal is A
It is amplified by the amplification unit 26 with GC, further amplified by the amplification unit 28, and combined with the video intermediate frequency signal by the combiner 22.

Thus, the reason why the audio intermediate frequency signal and the video intermediate frequency signal are separated, amplified and then recombined is to set the levels of the audio intermediate frequency signal and the video intermediate frequency signal to desired levels. Is.

The audio and video intermediate frequency signals synthesized by the synthesizer 22 are amplified by the amplifying section 30, and SA
After the unnecessary harmonic component is removed by the W filter 32, it is amplified by the amplifier 34, further adjusted to a desired level by the level adjuster 36, and then supplied to the mute circuit 38.

An energizing signal is supplied to the mute circuit 38 from the intermediate frequency level detecting section 40. The intermediate frequency level detecting section 40 is supplied with a video intermediate frequency signal branched from the branch output side of the one-branching device 18 and amplified by the amplifying section 42, and the video intermediate frequency signal from the amplifying section 42 is predetermined. If the level is above the level, the energizing signal is supplied to the mute circuit 38, and the video and audio intermediate frequency signals from the level adjuster 36 are output to the output terminal 44. On the other hand, the amplification unit 4
When the image intermediate frequency signal from 2 is not higher than a predetermined level, the energizing signal is not generated from the intermediate frequency level detector 40, and the image and audio intermediate frequency signals from the level adjuster 36 are cut off, that is, muted. Is not supplied to the output terminal 44.

The video and audio intermediate frequency signals generated at the output terminal 44 are supplied to the up converter 48 via the input terminal 46.
To a high frequency audio signal and a high frequency image signal of a desired frequency higher than the intermediate frequency signal of the video and audio signals, and output to the output terminal 50.

[0010]

In the above channel processor, whether or not to operate the mute circuit 38 is determined only by whether or not the level of the video intermediate frequency signal is above a predetermined level. Therefore, even if the video and audio intermediate frequency signals do not exist, for example, audio F having a level higher than a predetermined level in the vicinity of these frequencies.
When the M signal or the like is present, there is a problem that the unnecessary audio FM signal is output to the up converter 48 without being muted.

[0011]

SUMMARY OF THE INVENTION To solve the above problems, the present invention provides a signal source and a signal from the signal source, which passes the signal when an energizing signal is supplied. Muting means, a level detecting means for generating a first output signal when the signal is above a predetermined level, a reference signal detecting means for generating a second output signal when the signal includes a reference signal, And a mute control means for supplying the energizing signal to the mute means when both the second output signal and the second output signal are inputted.

[0012]

According to the present invention, the level detecting means generates the first output signal when the signal from the signal source is equal to or higher than the predetermined level, and the reference signal detecting means when the signal from the signal source includes the reference signal. Produces a second output signal. When both the first and second output signals are supplied, the mute control means supplies the energizing signal to the mute means, and the mute means passes the signal from the signal source. Therefore, even if the signal from the signal source is above the predetermined level, the mute means does not pass the signal from the signal source when the signal from the signal source does not include the reference signal.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In this embodiment, as shown in FIG. 1, the present invention is applied to a mute device used for a channel processor. A television broadcast signal received by an antenna (not shown) via an input terminal 52 is received by a tuner 54. Is supplied to. The tuner 54 receives and demodulates the television broadcast signal, outputs the baseband audio signal to the audio output terminal 56 and the baseband video signal to the video output terminal 58, and also amplifies the video and audio intermediate frequency signals. 60
Output to.

The video and audio intermediate frequency signals are amplified by the amplifier 60.
After being amplified by the SAW filter 62, unnecessary high frequency components are removed by
Is amplified by. The output of the amplification unit with AGC 64 is branched by the one-branching unit 66, the branched output is amplified by the amplification unit 68, and then divided into two by the two-divider 70, and one of the divided outputs is used as the AGC control signal. It is fed back to the amplification unit 64 with AGC.

The output signal of the one-branching device 66 is directly supplied to the mute circuit 74 via the changeover switch 72. Further, the output signal of the one-branching device 66 is also supplied to the amplifying unit 76 via the changeover switch 72, and after being amplified here,
The output is branched by the branching device 78, the branched output is supplied to the SAW filter 80, only the audio intermediate frequency signal is extracted, and is amplified to a predetermined level by the amplification unit 82 with AGC.

The output signal of the 1-branching device 78 is supplied to the SAW filter 84 and the video intermediate frequency signal is extracted.
The video intermediate frequency signal is amplified by the amplifier 86, adjusted to a desired level by the level adjuster 88, combined with the audio intermediate frequency signal by the combiner 90, and supplied to the mute circuit 74.

In this way, the changeover switch 72 is switched to the terminal 72a so as to directly supply the video and audio intermediate frequency signals to the mute circuit 74 when the audio signal exists outside the audio subcarrier band (for example, NICAM7).
This is because the SAW filter 80 directly supplies the audio signal to the mute circuit 74 so that the audio signal is not cut. On the other hand, change the switch 72 to the terminal 72b.
To separate the video and audio intermediate frequency signals,
After amplification, it is supplied to the mute circuit 74. The NICAM728 signal is used to multiplex digital stereo sound into terrestrial television broadcasting in the United Kingdom and Northern European countries. This is to place an audio carrier at a frequency higher than the video carrier by 5.5 MHz, FM-modulate this audio carrier with an audio signal,
A digital voice carrier is arranged at a frequency higher by 0.35 MHz than this voice carrier, and this digital voice carrier is DQPSK modulated to transmit digital voice data. A television broadcast signal in which voice multiplexing is performed by such a NICAM728 signal is SAW
When supplied to the filters 80 and 84, a part of the digital audio data is cut by the narrow band SAW filter 80, and the stereo audio is satisfactorily output to the rear mute circuit 74.
Cannot be supplied to. Therefore, when the digital voice data is included, the changeover switch 72 is changed over to the terminal 72a side.

The mute circuit 74 outputs the input signal to the output terminal 92 when the energizing signal is supplied. For example, as shown in FIG. 2, a PIN diode 94 having a cathode connected to the output terminal 92 is provided. And its cathode is grounded through a grounding resistor 96. Also,
The anode is a DC blocking capacitor 97, the changeover switch 72
It is connected to the branching device 66 side and to the combiner 90 via.

Further, the anode of the PIN diode 94 is connected to the AND circuit 100 via the high frequency blocking coil 98. Then, when a voltage of 5 V is applied as an H level from the AND circuit 100, for example, the high frequency blocking coil 98, the PIN diode 94, and the grounding resistor 9
6, the high-frequency resistance value of the PIN diode 94 decreases, and the video and audio intermediate frequency signals are output to the output terminal 92.
However, when a voltage of 0 V is applied as an L level from the AND circuit 100, the PIN diode 94 generates a large high frequency resistance value, and the video and audio intermediate frequency signals are output to the output terminal 92. Block.

An output signal from the intermediate frequency level detecting section 102 is supplied to the input terminal 102a of the AND circuit 100. The intermediate frequency level detecting unit 102 is supplied with the distributed output from the two-way distributor 70 (the intermediate frequency signal of the video and audio output from the amplifier 64 with AGC is amplified by the amplifying unit 68), and this distributed output is supplied. When the level is higher than a predetermined level, the H level signal is sent to the AND circuit 10
It is configured to supply 0.

An output signal is also supplied from the synchronization detecting section 104 to the input terminal 100b of the AND circuit 100. A baseband video signal is supplied from the video output terminal 58 of the tuner 54 to the synchronization detection unit 104. When the synchronization signal is detected from the baseband video signal, the synchronization detection unit 104 ANDs the H level signal. It is configured to supply the circuit 100.

Therefore, the AND circuit 100 supplies the H level energizing signal to the mute circuit 74 only when the level of the output signal of the amplifying section 68 is equal to or higher than a predetermined level and when the synchronizing signal is detected. At this time, the branching device 66 or the combiner 9 supplied via the changeover switch 72
Since the output signal from 0 is a video and audio intermediate frequency signal and has a predetermined level or more, the mute circuit 7
4 and is supplied to the output terminal 92.

On the other hand, when the level of the output signal of the amplifier 68 is equal to or higher than a predetermined level, but the sync signal is not detected,
The AND circuit 100 generates an L level signal. At this time, the output signal from the branching device 66 or the combiner 90 supplied via the changeover switch 72 is not a video and audio intermediate frequency signal, and is therefore cut off by the mute circuit 74.

Further, when the level of the output signal of the amplifier 68 is not higher than a predetermined level and no sync signal is detected, A
The ND circuit 100 generates an L level signal. At this time, the switch 6 supplied through the changeover switch 72
6 or the output signal from the synthesizer 90 is not a video and audio intermediate frequency signal, and is cut off by the mute circuit 74.

When the level of the output signal of the amplifier 68 is not higher than the predetermined level and the sync signal is detected, the AND signal is output.
The circuit 100 generates an L level signal. At this time,
The output signal from the branching device 66 or the combiner 90 supplied via the changeover switch 72 is a video and audio intermediate frequency signal, but its level is low, so the mute circuit 74 is used.
Blocked by.

The video and audio intermediate frequency signals supplied to the output terminal 92 are supplied to the up-converter 108 via the input terminal 106 where they are converted to a desired frequency higher than the video and audio intermediate frequency signals. Output terminal 110
Is output from.

In the above embodiment, the mute device according to the present invention is implemented in the channel processor, but other devices,
For example, it can be used as a receiver. Of course, the signal received by the receiver includes a reference signal such as a synchronization signal. Further, in the above embodiment, the changeover switch 72 is used to directly output the video and audio intermediate frequency signals.
4 and a case where the video and audio intermediate frequency signals are separately amplified and then synthesized, and then the mute circuit 74.
It is configured so that it can be switched between the case of supplying to any of the above, but it is also possible to provide only one of them. Further, although the sync signal is detected from the baseband video signal, the sync signal may be detected from the video intermediate frequency signal.

[0028]

As described above, according to the present invention, the signal from the signal source is passed only when the signal from the signal source is equal to or higher than a predetermined level and further includes the reference signal, In the cases other than the above, since the signal from the signal source is configured to be blocked, it is possible to reliably block an undesired signal having a level equal to or higher than a predetermined level, although the reference signal is not included.

[Brief description of drawings]

FIG. 1 is a block diagram of one embodiment of a channel processor implementing a mute device according to the present invention.

FIG. 2 is a circuit diagram of a mute device used in the embodiment.

FIG. 3 is a block diagram of one embodiment of a channel processor implementing a conventional mute device.

[Explanation of symbols]

 54 Tuner (Signal Source) 74 Mute Device (Mute Means) 100 AND Circuit (Mute Control Circuit) 102 Intermediate Frequency Level Detection Unit (Level Detection Means) 104 Synchronization Detection Unit (Reference Signal Detection Means)

Claims (1)

[Claims] 1. A signal source, a mute means for supplying a signal from the signal source and passing the signal when an energizing signal is supplied, and a first output signal when the signal is at a predetermined level or higher. Level detecting means for generating, a reference signal detecting means for generating a second output signal when the signal includes a reference signal, and the energizing signal for the mute means when both the first and second output signals are input. A mute device comprising a mute control means for supplying.