JPH069266U - Magnetic tape unit - Google Patents

Abstract

(57) [Summary] [Purpose] A mute-controlled magnetic tape device that prevents noise generated during channel selection during VTR channel switching. When the channel of the VTR is selected, the control circuit microcomputer 2 sends tuning data to the tuner 3 and at the same time sends a mute signal to the mute circuit 1 to perform video mute. When the mute is released after the end of the channel selection period, the video signal and the audio signal are input to the video circuit and subjected to signal processing, and then become a television signal wave in the RF modulator circuit 5, and the television receiver 6 becomes empty through the changeover switch 7. Received on channel.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to mute control of a video signal when switching channels of a magnetic tape device.

[0002]

[Prior art]

 When supplying a television broadcast reception signal from a built-in television tuner to a magnetic tape device, especially a video tape recorder (hereinafter referred to as a VTR), when the tuner is selected, an unsightly screen or uncomfortable noise is caused by inter-station noise. Occurs. Therefore, a method of muting the video and audio signals on the tuner side during tuning was considered.

FIG. 3 is a block diagram of conventional video mute control. Here, 131 is a mute control switching transistor, 132 is a mute signal input terminal, and 134 is a video signal input terminal. Further, 5 is an RF modulator, and 112 is an RF output terminal. The operation of the mute circuit installed after the video circuit is as follows. At the time of channel switching, a video mute signal is formed in a time width corresponding to the channel selection time in synchronization with the channel selection scanning pulse. The video mute signal is supplied from its input terminal 132 to the switching transistor 131. As a result, the switching transistor 131 is switched from OFF to ON, the video signal 134 is set to 0 potential, and the image is muted.

[0004]

[Problems to be solved by the device]

 However, in the conventional technique shown in FIG. 3, since the mute circuit is provided after the video circuit for performing various signal processing, there is a problem that the adverse effect due to the level variation is likely to occur. Also, the mute is divided into the image signal and the sync signal period, only the image signal is muted, and the pre-sync processing is performed on the receiver.However, the phase of the sync signal of the new channel selected and switched is Since it is different from the previous channel, it increases the double labor of setting the mute time so that the mute of the video and audio signals will be continued until it is completely synchronized after the new channel selection. There is a problem that the circuit configuration becomes complicated.

Further, in the case of the electronic tuning system, since the tuning time is compressed, the image contents are switched at an early timing immediately after the occurrence of the tuning operation pulse, and the receiver side sees the advance synchronization process and new synchronization. There is a problem that the timing of receiving the image contents due to channel selection overlaps, and the preceding synchronization process is meaningless.

The present invention has been made in view of the above circumstances, and a mute circuit having a simple structure is provided on the tuner circuit side, not after the video circuit, to cause adverse effects due to signal level fluctuations. It is an object of the present invention to provide a magnetic tape device which does not effectively perform video mute.

[0007]

[Means for Solving the Problems]

 In order to achieve the above object, the present invention is characterized in that a video mute circuit controlled by a mute signal from a control circuit is provided on the tuner circuit side when switching channels of broadcast signal waves.

[0008]

[Action]

 With the above configuration, the control circuit obtains tuning data, and at the same time sends a mute signal to the video mute circuit on the tuner circuit side to perform video mute, so that the generation of noise during the tuning period of the tuner can be prevented. .

[0009]

【Example】

 An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of a video signal mute circuit according to the present invention. FIG. 2 is a block diagram of the VTR. First, the reference numerals in FIG. 2 which are hole drawings of the entire VTR will be described. Here, 1 is a mute circuit, 3 is a tuner, 4 is a video circuit, 5 is an RF modulator circuit, 2 is a control circuit microcomputer, 2a is a channel selection data output terminal, 2b is a mute signal output terminal, and 6 is a television receiver. Machine, 7 is a changeover switch, 8 is a magnetic tape, 9 is a distributor, and 10 is an antenna.

A block diagram of the mute circuit 1 in FIG. 2 is shown in FIG. Here, 11 is a switching transistor for mute, and 12 is a mute signal input terminal. A circuit 30 receives the video IF signal from the tuner 3 and amplifies the video IF signal until it is output to the video circuit 4. Here, 31 and 32 are input terminals for the video IF signal from the tuner 3, and 33 is an output terminal for the video signal that has been subjected to processing such as IF signal amplification, and this output signal is sent to the video circuit 4. Further, 34 is an automatic gain control (AGC) circuit of an IF amplifier circuit, and 35 and 36 are amplifier circuits.

In these figures, when recording with a VTR and monitoring with a television receiver, press the video / television button on the remote control in the connection state shown in FIG. The tuner 3 selects the recording channel by pressing the channel button on the remote control.

When the recording button is pressed, the VTR recording display is displayed, and the channel selected by the tuner 3 via the antenna 10 and the distributor 9 is recorded on the magnetic tape 8 by the recording head while the video circuit 4 processes the signal. record. On the other hand, the TV signal of the selected channel is received and displayed by the RF circuit 5 and the switch 7 (on the video side) on an empty channel of, for example, 2ch of the TV receiver 6.

At this time, in order to prevent inter-station noise when channel selection is performed by the tuner 3 of the VTR, as shown in FIG. 1, the video mute circuit 1 at the output stage of the tuner 3 is provided before the video circuit 4 as shown in FIG. Is controlled by the control circuit microcomputer to mute the video signal of the tuner 3 during the tuning period to cut noise until the reception of the television receiver 6 becomes stable.

First, the control circuit microcomputer 2 sends the tuning data (tuning voltage, frequency division ratio, etc.) of the electronic tuning to be tuned to the tuner 3 from the terminal 2a and tunes to the mute circuit at the same time. Send the mute signal from the 2b terminal to 1.

The transmission timing of the mute signal is a pulse signal having a time width that covers the channel selection time starting from the channel selection data transmission time point. The mute signal voltage is applied to the AGC circuit 34 of the IF (intermediate frequency) amplifier circuit 35 to cut off the IF amplifier circuit. The mute voltage is supplied by inputting a signal that is turned on / off by a mute pulse from the terminal 2b of the control circuit microcomputer 2 to the switching transistor circuit 11 from the mute signal input terminal 12.

When the mute pulse is turned off after the tuning period has elapsed, the mute of the IF amplifier circuit is released and the original operation is restored, and the muted video signal and audio signal are normally sent to the video circuit 4. The input signal is converted into a TV wave by the RF modulator circuit 5 and output to the TV receiver 6. At this point, the unstable condition has disappeared during the tuning period, so stable images and sound can be obtained.

In this embodiment, by performing video mute on the tuner side of the VTR with a simple circuit configuration, it is possible to mute the video and audio signals accurately during channel selection.

[0018]

[Effect of device]

 As described above, according to the present invention, since the tuner circuit side is provided with the video mute circuit which is controlled by the mute signal from the control circuit when the channel of the VTR is switched, it is difficult for the television receiver to hear during the channel selection period. This has the effect of preventing inter-station noise such as noise and image distortion.

[Brief description of drawings]

FIG. 1 is a circuit diagram of video mute control of a VTR tuner of the present invention.

FIG. 2 is a block diagram of a VTR.

FIG. 3 is a circuit diagram of conventional video mute control.

[Explanation of symbols]

 1 Mute Circuit 2 Control Circuit Microcomputer 2a Channel Selection Data Output Terminal 2b Mute Signal Output Terminal 3 Tuner Circuit 4 Video Circuit 5 RF Modulator Circuit 6 Television Receiver 7 Changeover Switch 8 Magnetic Tape 9 Distributor 10 Antenna 11 Switching Transistor 12 Mute Signal Input terminal 30 IF amplifier circuit 31, 32 IF signal input terminal 33 IF signal output terminal 34 AGC circuit 35, 36 Amplifier circuit

Claims (1)

[Scope of utility model registration request] 1. A magnetic tape device comprising a tuner circuit side provided with a video mute circuit controlled by a mute signal from a control circuit at the time of channel switching of a broadcast signal wave.