JPS587986A - Vtr switching circuit - Google Patents

Abstract

PURPOSE:To make the switch for switching operation unnecessary and improve the reliability, by detecting the synchronizing signal in the video signal from a VTR connected in the external and switching the VTR to the reproducing signal monitor and the receiving operation of a TV broadcast in accordance with the presence and absence of the synchronizing signal. CONSTITUTION:The output of a video detecting and amplifying circuit 5 of a TV picture receiver is applied to one input of the first switching circuit 7, and the output of a sound detecting and amplifying circuit 6 is inputted to one input of the second switching circuit 8. A video input terminal 9a of a VTR9 connected in the external is connected to the other input of the circuit 7, and a sound input terminal 9b is connected to the other input of the circuit 8. The third switching circuit 10 is provided, and a voltage +B is supplied to each circuit of the TV picture receiver by this circuit 10, and a switching control signal is applied to circuit 7 and 8. The synchronizing signal from the VTR9 is detected by a synchronizing signal separating circuit 11 connected to the input terminal 9a and is compared with the fly-back pulse in a comparing circuit 12; an if they coincide with each other, the circuit 10 is controlled to switch the VTR9 to the receiving state automatically.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a VTR switching circuit when a general television receiver is used as a monitor receiver for a VTR (video tape recorder).

The following television receivers include this type of VTR switching circuit. This is equipped with an external operation switch to control the V'RA switching circuit, and by switching the switch to the TV side, TV broadcasts are received, and by switching to the VT It, side VC, it is connected to the TV receiver. It is designed so that a reproduced image of the V'r level can be obtained as soon as the VTlt i reproduction state is set.

However, the above-mentioned VTIL switching circuit requires a switching operation at the time of switching, and in particular, since the external operation switch is usually a contact type, there is also a problem in terms of reliability.

An object of the present invention is to detect the synchronization signal of v'rit and use the synchronization signal 1 to automatically switch between television broadcast reception and V'rlL monitoring operation, thereby achieving the above-mentioned It is an object of the present invention to provide a VTrt switching circuit that solves such problems.

The detailed VCC development of the present invention has been described above with reference to embodiments.

In the figure, 1 is an antenna, 2 &:t cheese, 6 is a video intermediate frequency amplification circuit, 4 is an audio intermediate frequency amplification circuit, 5 is a video detection/amplification circuit, and 6 is an audio detection/amplification circuit.

The output of the video detection/amplification circuit 5 is then transferred to the first switching circuit 7.
The output of the line detection/amplification circuit 6 is input to one input terminal of the second switching circuit 8. On the other hand, the video input terminal 9a of the externally connected VTfl.9 is input to the other input terminal of the first switching circuit 7, and the audio input terminal 9b is input to the other input terminal of the second switching circuit 8. ing. Reference numeral 10 designates a third switching circuit which receives the 10B voltage and transmits its output to the cheese 2, the video intermediate frequency amplification circuit 6, the audio intermediate frequency amplification circuit 4, the video detection/amplification circuit 5, and the audio detection/amplification circuit 5. The voltage is sent to the amplifier circuit 6 as a voltage of 10 B, and to the first switching circuit 7 and second switching circuit 8 as a switching control signal. 11 is VTI't
This is a synchronization separation circuit that separates and extracts a horizontal synchronization signal from the video output from the comparison circuit 12, and the horizontal synchronization signal from there is inputted to one input terminal of the comparison circuit 12. This comparison circuit 1
2 inputs a horizontal oscillation flyback pulse for AFO generated from a flyback transformer inside the television receiver as a comparison reference signal, and when the signal from the synchronization separation circuit 11 has the same frequency as the flyback pulse,
``It is designed to confirm that the signal is a horizontal synchronization signal, activate the output signal, and control the third switching circuit 10.'' Note that this comparison circuit 12
F/V converts the frequency of 1 to 2 to DC rIi and pressure
Conversion A (1-"/V converter that converts the frequency of the flyback pulse to DC 19' voltage, and the output voltage 1F of both 1i'/V converters is manually powered 17, and when both voltages match, the so-called DC It can be constructed by a comparator that generates all voltages.

In the past, the first switching circuit 7, the second switching circuit (laughing time 48, and f
r 3 switching circuit 10; J-, transistor or F1 switch
It is possible to configure a non-contact type trowel using V.

The entire operation of the missing V'C will be explained. Now, when the VTIL 9 is not operating, the synchronization separation circuit 11 has no human input signal, so there is no output value ν), and therefore the output signal of the comparison circuit 12 is inactive. Therefore, the third switching circuit 10 which receives the output (1' as the control signal number) outputs the +Bffi pressure applied to the input terminal, the cheese 2, the video intermediate frequency amplification circuit 6, the audio intermediate frequency amplification circuit 4, and the video It is applied to the detection/amplification circuit 5 and the audio detection/amplification circuit 6 to make those circuits operate normally.The 10B city pressure is also applied to the first switching circuit 7 and the second J switching circuit 8. The control circuit 16 selects the output signal of the video detection/amplification circuit 5, and the second switching circuit 8 selects the output signal of the audio detection/amplification circuit 6. Therefore, when the VTI-L 9 is not operating as described above, the received television broadcast video signal is
The audio signal of the received television broadcast is output from the switching circuit 7 and is output from the second switching circuit 8.

On the other hand, when receiving such a TV broadcast, when the T-box 9 is operated to enter the playback state, a video signal is applied to the video input terminal 9a, a horizontal synchronizing signal is separated and extracted in the synchronization separation circuit 11, and the horizontal synchronization signal is separated and extracted. The signal becomes one input signal of the comparison circuit 12. At this time, a flyback pulse is applied to the other input of this comparator circuit 12, and in this case, both input signals have a frequency of 15.75 KHz, so the output signal of the comparator circuit 12 becomes active, and the third switching The circuit 10 no longer outputs the +B voltage. Therefore, Team 2
．． 1 video intermediate frequency amplification circuit 6, i-voice intermediate frequency amplification circuit 4
, video detection/amplification circuit 5, and audio detection/amplification circuit 6
At the same time, the first I/J switching circuit 7 and the second switching circuit 8 switch, and the first switching circuit 7 becomes VT.
The second switching circuit 8 selects the video signal from the VTR.
It becomes K when selecting the audio signal from 9.

Therefore, when the VTR 9 performs playback operation as described above, reception of television broadcasting is stopped, the video signal of the VTIL 9 is output from the @l switching circuit 7, and the V'r
Automatic switching is performed such that the audio signal of 几9 is output from the second switching circuit 8, and the +B! Pressure supply is stopped.

Then, when the reproduction operation of V'r II.9 is finished or stopped midway, the video signal disappears along with the audio signal, so the output signal of the comparator circuit 12 becomes inactive as described above, and the TV broadcast reception 4M state is reached. It will return automatically.

As described above, according to the VTft switching circuit of the present invention, the TV receiver automatically switches between V'RA image playback and TV broadcast reception depending on the reproduction operation/non-operation of the VTR 9 whose output is connected to the TV receiver. This eliminates the need for switching operations. Reliability is also improved.

[Brief explanation of the drawing]

The figure is a circuit diagram of a vT ratio switching circuit showing one embodiment of the present invention. Patent applicant General Co., Ltd.

Claims (5)

[Claims] (1) A VTR connected externally in a television receiver
1. A VTIL switching circuit characterized in that it detects a synchronizing signal in a video signal from a VTR, and switches between monitoring a reproduction signal of the VTR and receiving television broadcasting depending on the presence or absence of the synchronizing signal. (2) The VTR switching circuit according to claim 1, wherein the synchronization signal is a horizontal synchronization signal. (3) a first switching means for switching between the video signal from the VTR and the video signal for the television broadcast; a second switching means for switching between the audio signal from the VTR and the audio signal for the television broadcast; and the horizontal synchronization signal. 3. The VTR switching circuit according to claim 2, further comprising third switching means for controlling said first switching means and said second switching means depending on the presence or absence of said switching means. (4) The detection of the horizontal synchronization signal is performed by a comparison means for comparing the signal and a flyback pulse, which includes a synchronization separation means for separating and extracting the horizontal synchronization signal from the video signal from the VTR. A VTR and a switching circuit according to claim 2. (5) The VTR switching circuit according to claim 1, wherein the comparison means compares the output signal of the synchronization separation means and the frequency of the flyback pulse. (61. The VTIL switching circuit according to claim 3, wherein the third switching means simultaneously switches the power supplies of the high frequency circuit for receiving television broadcasting.