JPS58213569A - Device for switching video input - Google Patents

Abstract

PURPOSE:To automatically switch three video signals in accordance with the 2nd and 3rd pulsing signals generated correspondingly to the detection of the existence of the 1st and the 2nd video signals and the output of the existence detection of the video signals. CONSTITUTION:When the 2nd video signal exists, the 2nd video signal is selected and outputted with priority regardless of other video signals. When the 2nd video signal does not exist but the 3rd video signal exists, the 3rd video signal is selected and outputted irrespectively of the existence of the 1st video signal. When both 2nd and 3rd video signals do not exist, the 1st video signal is selected and outputted. That is to say, even when video signals are simultaneously inputted, a prescribed video signal is selected and outputted in accordance with a preset priority (in the order of the 2nd, the 3rd, and the 1st video signals). In addition to the above, the changeover of voice input signals are performed in the same way as in the case of video signals.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a video input switching device that can automatically switch each input signal, particularly in video equipment having multiple video input terminals such as television signals, VTR signals, and video disc signals. The present invention relates to a video input switching device.

For example, some television receivers have multiple video input terminals such as VTR signals and video disk signals. Such a television receiver is provided with a video input switching device for switching the video signal according to the input video signal. Some conventional video input switching devices use mechanical switch circuits. However, with such a video input switching device, it is necessary to manually switch the switch each time the video signal source changes, which is troublesome. In addition, there are the following video input switching devices for switching between two video signals. That is,
A constant DC voltage is superimposed on one of the video signals in advance.

Then, the constant DC voltage is detected, and the video signal is switched in accordance with the detection. For example, when a video signal on which a constant DC voltage is superimposed and a video signal on which a constant DC voltage is not superimposed are input, one or the other video signal is selected preferentially. However, in such a method, since it is necessary to superimpose a DC voltage on one of the video signals in advance, the video signal sources that can be switched are limited. Also,
In such a system, it is difficult to switch between three or more video signals.

Therefore, the main object of the present invention is to provide a video input switching device that has a simple configuration and can automatically switch between three video signals.

In summary, the present invention includes a first input terminal to which a first video signal is applied, a second input terminal to which a second video signal is applied, and a third input terminal to which a third video signal is applied. A terminal is provided, the presence or absence of a first video signal applied to the first input terminal and a second video signal applied to the second input terminal is detected, and a predetermined selection signal (a second 2 selection signal and a third selection signal), and selectively switches and outputs a predetermined video signal according to the second selection signal, the third selection signal, and the first video signal presence/absence detection output. This is how it was done.

The above objects and other objects and features of the present invention will become more apparent from the following detailed description with reference to the drawings.

FIG. 1 is a block diagram showing one embodiment of the present invention.

In the configuration, a first video input terminal 1. A video signal is applied to the second video input terminal 2115 and the third video input terminal 3 from a predetermined video signal source, for example, a television signal source, a VTR signal source, or a video disc signal source. These first video input terminals 1. The second video input terminal 2 and the third video input terminal 3 are each connected to a video signal switch 4. A selection signal is applied to the video signal switch 4 at its first input terminal 16, second input terminal 11, and third input terminal 18. Then, the video signal switch 4 selectively switches the video signal corresponding to this selection signal and outputs it to the output terminal 19.

FIG. 2 is a circuit diagram showing the detailed configuration of the video signal switching device 4 described above. In the figure, the video signal switch 4 is a relay 4 inserted between the first video input terminal 1 and the output terminal 19.
1, a relay 42 inserted between the second video input terminal 2 and the output terminal 19, and the third video input terminal 3 and the output terminal 1.
and a relay 43 inserted between the two. Furthermore, a transistor 44 controls on/off of the energizing current of the relay 41 in response to a selection signal applied to the first input terminal 16.
, a transistor 45 that controls on/off of the energizing current of the relay 42 in response to a selection signal applied to the second input terminal 11, and a transistor 45 that controls on/off of the energizing current of the relay 43 in response to a selection signal applied to the third input terminal 18. Controlling transistor 46
including. That is, when the selection signal is applied to the first input terminal 16, the video signal switch 4 selects and outputs the video signal from the first video input terminal 1. Further, when the selection signal is given to the second input terminal 11, the second video input terminal 2
Select and output the video signal from. Further, when a selection signal is applied to the third input terminal 18, the video signal from the third video input terminal 3 is selected and output.

Referring again to FIG. 1, the second video input terminal 2 is connected to the synchronization signal separation circuit 5. The synchronizing signal separated by the synchronizing signal separation circuit 5 is given to an integrating circuit 6. The synchronizing signal separation circuit 5 and the integrating circuit 6 constitute means for detecting whether or not a video signal is applied to the second video input terminal 2. That is, when a video signal is applied to the second video input terminal 2, the output of the integrating circuit 6 becomes a high level, and when no video signal is applied to the second video input terminal 2, the output of the integrating circuit 6 becomes a low level. Become. Similarly, the third video input terminal 3 is connected to a synchronization signal separation circuit 7 , and the synchronization signal separated by the synchronization signal separation circuit 7 is given to an integration circuit 8 . And the third video Jinrita 3
When a video signal is applied to the third video input terminal 3, the output of the integrating circuit 8 becomes high level, and when no video signal is applied to the third video input terminal 3, the output of the integrating circuit 8 becomes low level.

The outputs of integration circuits 6 and 8 are respectively connected to inverter 9.
and 12 to NAND goo 1-14. The output of the NAND gate 14 is applied to a first input terminal 16 of the video signal switch 4 via an inverter 15. These inverters 9 and 12. NAND gate 1
4 and the inverter 15 constitute selection signal generating means for selecting the first video signal (the video signal applied to the first video input terminal 1). In addition, the output of the integrating circuit 6 is directly applied to the second input terminal 11 of the video signal switch 4. That is, the output of the integrating circuit 6 acts as a signal for directly selecting the second video signal (the video signal applied to the second input terminal 2). Furthermore, the output of the integrating circuit 6- is NAN
It is applied to one input of the O gate 10. The output of the integrating circuit 8 is applied to the other input of the NANO game 1-10. The output of NΔND gate 10 is NΔND gate 13
is given to one input. The output of the integrating circuit 8 is given to the other input of this NAND gate t-13.

The output of the NAND gate 13 is applied to a third input terminal 18 of the video signal switch 4 via an inverter 17. That is, NAND gates 10 and 13 and inverter 17
and constitute a selection signal generating means for selecting the third video signal (the video signal applied to the third video input terminal 3). Note that the video signal output from the output terminal 19 of the video 41A signal switch 4 is given to the video signal processing circuit 20. Although not shown, the video signal processing circuit 20 includes, for example, a video amplification circuit, a synchronization signal separation circuit, a color demodulation circuit, and the like.゛Figure 3 shows the first video input terminal 1. the presence or absence of a video signal given to the second video input terminal 2 and the third video input terminal 3;
First input terminal 16. 5 is a diagram showing the relationship between the level states of the second input terminal 11 and the third input terminal 18. FIG. In addition, O
The mark indicates when a video signal is input, and the x mark indicates when no video signal is input.

Further, H in the lower part of FIG. 3 indicates a high level, and 2 indicates a low level. Figure 4 shows each state 1 in Figure 3.
Integrating circuit corresponding to 6. to 8. Integrating circuit 8. NAND
Gate 10. 3 is a diagram showing output level states of each of NAND gate 13 and NAND gate 14. FIG. Note that in FIG. 4, H indicates a high level, and L indicates a low level.

Hereinafter, with reference to Figures 3 and 4, Figures 1 and 2 will be explained.
The operation shown in the figure will be explained.

First, the state H1 shows a state in which there is no video signal at all of the video input terminals 1 to 3, and the state 12 shows a state in which there is a video signal only in the video input terminal 1.

In these states 1 and 2, as shown in FIG. 4, the outputs of the integrating circuits 6 and 8 are both at low level. Therefore, the output of NAND gate 14 is at a low level, and the output of NAND gate 10 is at a high level. Therefore, in this case, a high level selection signal is applied only to input terminal 16. Accordingly, the video signal switch 4 selectively switches and outputs the video signal from the video input terminal 1.

Next, the cases of states 4 and 6 will be explained.

In this case, a video signal is provided to the third video input terminal 3, but no video signal is provided to the second video human force sensor 2. Therefore, as shown in FIG. 4, the output of the integrating circuit 6 is at a low level, and the output of the integrating circuit 8 is at a high level. Therefore, the output of the NAND gate 14 becomes high level, and the output of the NAND gate 13 becomes low level. That is, in this case, a high level selection signal is applied only to the third input terminal 18 of the video signal switch 4. Accordingly, the video signal switch 4 selectively switches and outputs the video WIA signal from the third video input terminal 3.

In cases other than the state explained above, that is, state 3゜5.7
In the case of 8 and 8, the video signal is provided to the second video input terminal 2. In this case, as shown in FIG. 4', the outputs of NAND gates 13 and 14 are at a high level in either state. Therefore, in the video signal switch 4, a high level selection @ signal is applied only to the second input terminal 11. Accordingly, the video signal switch 4 selectively switches and outputs the video signal from the second video input terminal 2.

To summarize the above operation description, if there is a second video signal, the second video signal is selected and output with priority regardless of other video signals. If there is a third video signal when there is no second video signal, the third video signal is selected and output regardless of the presence or absence of the first video signal.

Furthermore, if there is no second video signal or third video signal, the first video signal is selected and output. That is, in this embodiment, even if the video signals are input at the same time, the priority order (second video signal, third video signal, etc.) is determined in advance.

A predetermined video signal is selected and output according to the order of the first video signal). Note that in the above embodiment, the audio input signal switching device is omitted, but the switching is performed in the same way as the video signal switching. . Further, in the above embodiment, the switching signal is generated by the NΔND gate and the inverter, but other
- A similar operation is possible using the element 10. Therefore, the present invention is not limited to only the 1M configuration.

In addition, in the embodiment e described above, the presence or absence of a video signal is detected based on the synchronization signal of the video signal, but in the case of a color video signal, the presence or absence is detected based on a burst signal. You can also do that.

Alternatively, the presence or absence may be detected based on the audio carrier wave.

As described above, according to the present invention, it is possible to selectively switch and output a predetermined video number 1N depending on the presence or absence of three video signals. Therefore, there is no need to perform troublesome manual switching as in the prior art, and the video signal source to be switched is not limited.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of the present invention. FIG. 2 is a circuit diagram showing the detailed configuration of the video signal switch 4. As shown in FIG. Figure 3 shows the video 11 of the first to third video input terminals.
7 is a diagram showing the presence or absence of a signal and the state of the output level of the first to first third input terminals 16, 11 and 18 for each state. FIG. FIG. 4 is a diagram showing output level states of integration circuits 6 and 8 and NΔAND gates 10.13 and 14 corresponding to each state in FIG. 3. In the figure, 11 is a first video input terminal, 2 is a second video input terminal, 3 is a third video input terminal, 4 is a video signal switch, and 5
and 7 is a synchronization signal separation circuit, 6 and 8 are integration circuits,
9, 12, 15 and 17 are inverters, and 10, 13 and 14 are NAND gates. Agent Shin Kuzuno - (1 other person)
Figure 2 Figure 3 Figure 4 373-

Claims (2)

[Claims] (1) A first input terminal to which a first video signal is applied; a second input terminal to which a second image signal is applied; a third input terminal to which a third image signal is applied; A terminal provided in association with the input terminal, whose output is at a first level when the first video signal is applied, and whose output is at a second level when the first video signal is not applied. 1 video signal presence/absence detection means, provided in association with the second input terminal, whose output becomes a first level when the second video signal is applied, and when the second video signal is not applied; a second video signal presence/absence detection means whose output is at a second level when the output of the first video signal presence/absence detection means is at the second level and the output of the second video signal presence/absence detection means is at the second level; a second selection signal generation means for generating a second selection signal for selecting the second video signal only when the level is 1, the first video signal presence/absence detection means and the second video signal presence/absence detection means; third selection signal generating means for generating a third selection signal for selecting the third video signal only when both outputs are at the second level, and the first input terminal and the second input; The terminal is connected to the third input terminal, and the output of the first video signal presence/absence detection means, the second selection signal, and the third selection signal are applied to detect the presence/absence of the first video signal. selectively outputting the first video signal when the output is at the first level; selectively outputting the second one video signal in response to the second selection signal; A video input switching device comprising means for selectively outputting the third video signal in response to a signal. (2) The first video signal presence/absence detection means includes means for detecting the presence/absence of the first video signal based on a synchronization signal included in the first video signal, and the second video signal presence/absence detection means includes a means for detecting the presence/absence of the first video signal based on a synchronization signal included in the first video signal. The video input switching device according to claim 1, further comprising means for detecting the presence or absence of the synchronization signal based on a synchronization signal included in the video signal.