JPS6339149B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a signal switching device such as a video/audio switching device used in CCTV, CATV, and the like.

A conventional automatic video/audio switching device of this type will be explained with reference to FIG. In FIG. 1, 1 is a terminal to which one video signal (hereinafter referred to as input 1) is applied, 2 is a terminal to which the other video signal (hereinafter referred to as input 2) is applied, and 3 is a terminal to which terminal 1 is applied. a signal detection circuit that detects that "input 1" is applied; 4 is a transistor that is turned on by the output of this signal detection circuit 3; 5 is a relay whose relay coil is connected to the collector of the transistor 4;
Contact a of the relay contact is connected to the terminal 1, and contact b of the relay contact is connected to the terminal 2.

In the above configuration, "input 1" is partially determined by the signal detection circuit 3 to determine the presence or absence of the signal, so if there is a signal, the transistor 4 is made conductive, the relay 5 is activated, and the relay contact is set to the a side. knock down. As a result, “input 1” is output to the output terminal 6. On the other hand, when there is no "input 1", the transistor 4 is in a cut-off state and the relay contact is tilted to the b side, so that "input 2" is outputted to the output terminal 6. Although not shown, the audio signal is switched by a relay in conjunction with the video signal.

Therefore, according to the configuration of FIG. 1, "input 1"
When there is no input, "input 2" is output to the output terminal 6, and when there is "input 1", the output of "input 1" is output to the output terminal 6, and this is automatically switched.

However, in this case, when using the "input 2" signal, you may accidentally connect the "input 1" signal to terminal 1.
In addition, since the output automatically switches to "input 1", such an error is not allowed, and conversely, the problem arises that the "input 1" signal cannot be used at this time. Ta.

The present invention solves the above problem, and the “input 1”
and "Input 2" automatic switching function, and the "Input 1" signal cannot interrupt when the "Input 2" signal is being used, and the "Input 2" signal cannot be received. The purpose of the present invention is to provide a video/audio switching device that can use the "input 1" signal when

An embodiment of the present invention will be described below with reference to FIG. In the figure, elements and parts having the same functions as those in FIG. 1 are given the same numbers and explained.

In FIG. 2, a distributor 7 is first connected to the terminal 1 to which "input 1" is applied, and the output terminal of the distributor 7 is connected to the input terminal of the signal detection circuit 3, and one matching resistor 8 is connected. are connected to the output terminal 9 through the matching resistor 10, and to the relay contact a through the other matching resistor 10. Further, a switch 11 is inserted into the base of the transistor 4, and one terminal a of this switch 11 is left as an empty terminal, and the other terminal b is connected to ground. The other configurations are the same as in FIG. 1.

In the above configuration, if you want to automatically switch between "input 1" and "input 2" signals, switch 11
Connect the movable terminal of to terminal a. The operation at this time is similar to that shown in Figure 1. When "input 1" is applied to terminal 1, transistor 4 becomes conductive, and the relay contact becomes a.
It falls to the side, and the "input 1" signal is output from output terminals 6 and 9, and there is no "input 1" and "input 2"
When is applied to terminal 2, since the relay contact is tilted to the b side, an "input 2" signal is output to output terminal 6.

On the other hand, if the movable terminal of the switch 11 is connected to the terminal b side, regardless of the presence or absence of the "input 1" signal,
The “input 2” signal is output to the output terminal 6.
That is, this switch 11 is switched when it is desired to prevent automatic switching. At this time, even if "input 1" is applied, the transistor 4 is kept in the cut-off state by the switch 11, and the relay contact is located on the b side. The output terminal 6 remains unchanged, and the "input 2" signal is output to the output terminal 6. On the other hand, at this time,
The signal of "input 1" is output from the output terminal 9, and there is no longer a problem that the signal of "input 1" cannot be used when "input 2" is used as in the conventional case.

As explained above, according to the present invention, two different
The advantage is that it is possible to automatically switch between two input signals, and that it is possible to stop the automatic switching operation to prevent interruption of the other input signal while using one input signal, while still being able to use both input signals. It has extremely high practical value.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a conventional signal switching device, and FIG. 2 is a circuit diagram of a signal switching device according to an embodiment of the present invention. 1, 2...Input terminal, 3...Signal detection circuit, 4
...transistor, 5...relay, 6,9...output terminal, 7...distributor, 8,10...matching resistor, 11...switch.

Claims (1)

[Claims] 1 a first terminal to which a first input signal is applied, and a second terminal to which a first input signal is applied;
a second terminal to which an input signal is applied; a detection circuit for detecting the presence or absence of a first input signal at the first terminal; and a detection circuit for detecting the presence or absence of a first input signal at the first terminal; a terminal is connected to a first output terminal, and when the first input signal is applied to the first terminal, it is operated by the output of the detection circuit to switch the first terminal to a first output terminal. a second output terminal connected to the first input terminal; and a switch for bypassing the output signal of the signal detection circuit so as not to apply the output signal to the switching means. A signal switching device comprising: