JPS6231276A - Signal change over device - Google Patents

Abstract

PURPOSE:To prevent an abnormal noise from being outputted during a change over by using switches of two circuits, providing a defeat circuit and operating the defeat circuit to cut off a signal during a transition of a change over by one switch. CONSTITUTION:Non shorting type switches 1, 11 have, for example, respectively four fixed elements I, II, III, IV and movable terminals are connected to one another through resistances 3. Normally, a movable terminal of a switch is connected to any terminal and the movable terminal of the switch 11 is connected to an earth, so that a transistor 4 is cut off and a signal selected in a change over circuit 2 is outputted as it is and supplied to a next step circuit. During a change over, there is a fear that noises are produced. At that time, +B voltage is applied to a base of the transistor 4 through the resistance 3, so that the transistor 3 is turned on, and an output signal of the change over circuit 2 is dropped to the earth. The defeat function operates and even when the noises from the change over circuit 2 are produced, they are not outputted.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a signal switching device that switches between a plurality of video and audio signals, such as television signals and VTR playback signals, using a mechanical switch.

BACKGROUND OF THE INVENTION In recent years, with the development of new media, television receivers are equipped with multiple video and audio input terminals, and a video tape recorder (VTR) is connected to these terminals.

Connect a video disc player, etc. and receive a TV signal.

It has become possible to selectively switch a VTR playback signal or a video signal from a video disc, etc., and output it to a cathode ray tube and a speaker, thereby enjoying each video and audio.

A conventional signal switching device will be described below with reference to the drawings.

FIG. 2 shows an example of a conventional signal switching device. In the figure, numeral 1 is a non-shorting type mechanical switch, and numeral 2 is a four-circuit switching circuit that is switched by a two-pit discrimination signal. This switching circuit 2 is a mechanical switch 1
Four systems can be switched by voltage applied to terminals A and B.

The operation will be explained below.

If the switch 1 is in the terminal I position, +B is not applied to the terminals A and H of the switching circuit 2, and they are "0.○", so
The switching circuit 2 selects the input position as shown. Further, the mode of the switching circuit 2 changes corresponding to each position of the switch 1. The relationship between this control input and audio output is shown in the table below.

Currently, the switching circuit 2 is used for audio switching, but the switch 1 is also used for a video switching circuit. For that reason,
The switching timing of switch 1 uses a non-shorting type. If this is the 7 yawting type, input I when switching.

This is because (2) or the signals of inputs (2) and (2) are superimposed and output. Therefore, a non-shorting type switch is used to prevent multiple audio inputs from being output in a superimposed manner when switching.In this case, switch 1 is connected to either terminal when switching. A situation arises where this is not the case.

At this time, the switching circuit 2 becomes the "o, ○" mode.

That is, at the time of switching, the switching circuit 2 is in the mode of input I,
This signal will be output, resulting in an abnormal sound (noise) when switching.

Problems to be Solved by the Invention As described above, the conventional configuration had the problem that when the switch 1 was switched, the [o, oJ mode was entered, and an abnormal sound (noise) was produced.

In view of the above problems, the present invention provides a signal switching device that can eliminate abnormal sounds during switching.

Means for Solving the Problems To achieve this objective, the signal switching device of the present invention comprises:
Two circuits of switches are provided, and a defeat circuit is provided in the signal output circuit, one circuit of the switch controls signal switching, the other circuit controls the defeat circuit, and the switch connects to either contact. The defeat circuit is controlled to operate only when the cable is not connected, thereby preventing the generation of abnormal noise.

With this configuration, according to the signal switching device of the present invention, when the switch is not connected to any of the contacts at the time of switching, the defeat circuit works to prevent the signal from passing, so abnormal noises at the time of switching are suppressed. It can be eliminated.

EXAMPLE Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 shows the configuration of a signal switching circuit in one embodiment of the present invention. In Figure 1, 1°11 is a non-shorting type switch, and in this example, each 4°
Two fixed terminals1. (2), III, and It/, and the movable terminals are connected to each other via a resistor 3. The movable terminal of one switch 1 that controls signal switching is connected to a 10B voltage terminal via a resistor. In addition, each of the fixed terminals II, III, and IV of the switch 1 except for the fixed terminal I are connected to the switching circuit 2 through a diode as in the conventional example.
It is connected to control terminals A and B of. On the other hand, switch 1
Each of the fixed terminals 1 to 1 is connected to the ground (reference potential). The collector-emitter of a transistor 4 constituting a defeat circuit is connected between the output terminal (line) of the switching circuit 2 and the ground, and the movable terminal of the switch 11 is connected to the base of the transistor 4. . The operation of the signal switching device configured as above, in which the switches 1.1.1 are switched in conjunction with each other, will be described below.

The switches 1 and 11 have non-shorting switching timing, and there is a timing during which the switches are not connected to any terminal during switching. Normally, the movable terminal of switch 1 is connected to one of the terminals and the movable terminal of switch 11 is connected to ground, so transistor 4 is in a cut-off state and the signal selected in switching circuit 2 is output as is. and then supplied to the next stage circuit. During switching, there may be a situation in which the movable terminal of switch 1.11 is not connected to any of the fixed terminals, which may cause noise.
Since a voltage of 10 B is applied to the base of the transistor 3 through the resistor 3, the transistor 3 is turned on, and the output signal of the switching circuit 2 is grounded. That is, even if the defeat function is activated and noise is generated from the switching circuit 2, this will not be output.

As described above, according to this embodiment, the two-circuit switch 1
, 11, and a defeat circuit is provided, and one of the switches 11 operates the defeat circuit to cut off the signal during the switching transition period, thereby making it possible to prevent abnormal sounds from being output during switching.

Effects of the Invention As described above, according to the present invention, in a switching circuit using a non-shorting switch, the defect circuit is controlled using a two-circuit switch, thereby eliminating abnormal noise during switching. The practical effect is that of a dog.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of a signal switching device according to an embodiment of the present invention, and FIG. 2 is a circuit diagram of a conventional signal switching circuit. 1.11...Switch, 2...Switching circuit, 4..., Defeat transistor. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2

Claims (1)

[Claims] It is equipped with a switching circuit that switches and outputs multiple input signals, and is equipped with a non-shorting type mechanical switch with two circuits to control the switching of this switching circuit, one of which controls the switching circuit, and the remaining One circuit controls the defeat circuit connected to the output system of the switching circuit, and when the switch is connected to any of the contacts, the defeat circuit is not operated, and no contact is connected to any of the contacts. A signal switching device characterized in that the defeat circuit is controlled so as to operate only when the defeat circuit is not connected.