JPH01253801A - Video signal input/output circuit - Google Patents

Abstract

PURPOSE:To monitor plural video signals by providing switches which change over an external video input signal and the other video signals. CONSTITUTION:An automatic recording level adjusting circuit 4, a manual recording level adjusting circuit 3 and the recording level adjusting system changeover switch 5 are provided previous to the recording circuit of the video signals, and the amplitudes of the video signals which are inputted automatically or by a manual operation to the recording circuit are set to appropriate values. When a changeover switch 8 is changed over to the side of a recording video at that time, an oscilloscope connected to a video output terminal 2 can monitor them to be the appropriate values or not. When the external video input signal is to be monitored, the changeover switch 8 is changed over to the side of an external video. Thus, plural video signals can be monitored.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a video tape recorder and a video tape recorder capable of recording a video input signal from an external video input terminal and reproducing the recorded signal. The present invention relates to a video signal input/output circuit used in recording and reproducing devices such as optical disk devices.

2. Description of the Related Art Conventionally, as shown in FIG. 4, a video signal recording/reproducing device has a manual recording level adjustment circuit 3 or an automatic recording level adjusting circuit 3 consisting of a variable resistor in a signal path from an external video input terminal 1 to a video output terminal 2. A level adjustment circuit 4 may be provided, and the outputs of the two circuits may be selected by a changeover switch 6 and outputted to the video signal recording circuit, or the output of the changeover switch 5 may be changed to a video signal as shown in FIG. It is configured to lead out to the recording circuit and also to the video output terminal 2. Furthermore, as shown in FIG. 6, the output of the changeover switch 6 is
The configuration was such that the signal was output to the video signal recording circuit via the M modulator 6, and the output of the FM demodulator 7 was output to the video output terminal 2.

Problems to be Solved by the Invention However, in conventional video signal recording and reproducing devices, the video signal output to the video output terminal 2 is either the video signal input from the external video input terminal or the other video signal. Therefore, if you connect a monitor TV or oscilloscope to video output terminal 2 and try to monitor the output signal, you can only monitor one type of signal, such as the external video input signal, recorded video signal, or playback video signal. However, there was a problem in that it was very inconvenient.

Means for Solving the Problems In order to solve the above problems, the video signal input/output circuit of the present invention is capable of monitoring multiple video signals by providing a switch for switching between an external video input signal and other video signals. It is characterized by having the following configuration.

Effect of the present invention With the above configuration, the external video input signal and
It is possible to monitor the recorded video signal and/or the reproduced video signal, and the above-mentioned problems can be solved.

Examples Examples of the present invention will be described below. Figures 1 and 2
FIG. 3 shows an embodiment of the present invention. In the figure, 1 is an external video input terminal, 2 is a video output terminal, 3 is a manual recording level adjustment circuit, 4 is an automatic recording level adjustment circuit, and 6 is a switch for switching the recording level adjustment method between automatic and manual. , 6 is an FM modulation circuit, 7 is an FM demodulation circuit, 8
is a changeover switch for switching the output signal to the video output terminal 2 between an external video input signal and another video signal.

To explain the example shown in FIG. 1, an automatic recording level adjustment circuit 4, a manual recording level adjustment circuit 3, and a recording level adjustment method changeover switch 6 are provided in front of the video signal recording circuit, and the recording circuit can be automatically or manually operated. Set the amplitude of the video signal input to the appropriate value. At this time, if the selector switch 8 is set to the recording video side, the video output terminal 2
It is possible to monitor whether the values are appropriate using an oscilloscope connected to the oscilloscope. Furthermore, if it is desired to monitor an external video input signal, the selector switch 8 can be switched to the external video side.

The example shown in Figure 2 is almost the same as the example shown in Figure 1, but
The difference is that a signal that has passed through both the FM modulation circuit 6 and the FM demodulation circuit 7 is input to the video signal changeover switch 8 instead of the recording video signal. By monitoring this signal, it is possible to check the quality of almost all the circuits through which the video signal passes between the external video input terminal and the output video terminal.

The example shown in FIG. 3 is intended to have both the functions of the examples shown in FIG. 1 and FIG. 2, and therefore uses a video signal changeover switch 9 operated by three people.

Effects of the Invention As described above, according to the present invention, both the amplitude of the external video input signal and the recorded video signal can be monitored.
For example, if the amplitude of the external video signal input as a recording source is too large than the normal value, the user may
If you want to manually match the recorded novel accurately, you can do so by turning the switch to the recording video side, and switching to the external video side has the effect of allowing you to check the amplitude of the external video signal. In addition, both the external video input signal and the video signal that has passed through the FM modulation/demodulation circuit can be monitored, so by setting the selector switch to the playback video side, you can check the operation of the recording/playback circuit as well as the overall frequency characteristics. This has the effect of allowing you to check the waveform and amplitude of the external video signal by switching to the external video side.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of the video signal input/output circuit of the present invention, and FIGS. 2 and 3 are block diagrams showing other embodiments of the same circuit. Figure 4. FIGS. 6 and 6 are block diagrams showing a conventional video signal recording and reproducing apparatus. 3...Manual recording level adjustment circuit, 4...
・Automatic recording level adjustment circuit, 6... Selector switch, 6... FM modulation circuit, 7... FM
Demodulation circuit, 8, 9... changeover switch. Name of agent: Patent attorney Toshio Nakao and 1 other person
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Claims (1)

[Claims] The video signal input from the external video signal input terminal is
There are two types of circuits: a circuit that outputs to the video output terminal through a manual or automatic recording level adjustment circuit, and a circuit that passes only through parts that are not involved in signal control, modulation, demodulation, etc., such as amplifiers and buffers, without passing through these circuits. 1. A video signal input/output circuit characterized in that a changeover switch is provided to switch between two circuit outputs, and either signal is taken out from the output terminal.