JPH0456497B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an antenna switching circuit that switches signals output from a video tape recorder to a television receiver, for example.

[Conventional technology]

FIG. 2 is a block diagram showing a conventional antenna switching circuit for a video tape recorder. In FIG. 2, the antenna switching device 1 is connected to a control device 10 via a control output line 5. As shown in FIG. This control output line 5 is connected to a power source E via a resistor R.

This antenna switching device 1 is a device that switches an output signal 4 to a television receiver between a video tape recorder playback signal 2 and an external antenna input signal 3 using a signal from a control device 10.

The control device 10 includes a controller 6 and a control switch 11, and is connected to an antenna changeover switch 8, a forced through switch 9, and a status display device 12.

The control device 10 controls the status display device 12 and the control output line 5 according to the states of the forced through switch 9 and the antenna changeover switch 8.

Next, the operation of the conventional antenna switching circuit for a video tape recorder shown in FIG. 2 will be explained.
First, the operation when the forced through switch 9 is off will be explained.

In this case, each time the antenna changeover switch 8 is turned on, the controller 6 inverts the level ("H" or "L") of the control output 7. This control output 7 causes the control switch 11 to output the control output 7.
It is controlled so that it is turned on when it is "H" and turned off when it is "L".

When the control switch 11 is turned on, the input to the antenna switching device 1 becomes "L", and the output signal 4 to the television receiver becomes the external antenna input signal 3.

Further, when the control switch 11 is turned off, the input to the antenna switching device 1 becomes "H", and the output signal 4 to the television receiver becomes the video tape recorder playback signal 2.

Next, the operation when the forced through switch 9 is on will be explained. The controller 6 outputs the control output 7 regardless of the input of the antenna selector switch 8.
is always set to "H", and the control switch 11 is in the on state.

At this time, the input of the antenna switching device 1 is "L"
Therefore, the output signal 4 to the television receiver remains the external antenna input signal 3.

As described above, the operator can switch the output signal 4 to the television receiver by operating the antenna changeover switch 8 and the forced through switch 9.

The status display device 12 also indicates that the output signal 4 to the television receiver is the video tape recorder playback signal 2,
This is a display device for informing the operator of the state of which of the external antenna input signals 3 is selected by the antenna switching device 1.

[Problem that the invention seeks to solve]

A conventional antenna switching circuit for a video tape recorder is constructed as described above, but the control device 10 is usually implemented as an IC, and requires four terminals as input/output terminals, making the terminals expensive. Not only that, but the number of connection lines to the control device 10 also increases, and especially when the device is located far away, long lead wires are required, which increases the cost.

Further, since the controller 6 judges the status based on the status of the forced through switch 9 and the antenna changeover switch 8, the controller 6 itself becomes very complicated and expensive.

The present invention has been made to solve these problems, and aims to provide an antenna switching circuit that can reduce the number of terminals and connection lines of a control device and also reduce costs.

[Means for solving problems]

The antenna switching circuit according to the present invention is connected to a control output line and is provided with a forced through switch.

[Effect]

In this invention, by connecting the forced through switch to the control output line, the controller directly reads the state of the control output line and controls the state display.

〔Example〕

Embodiments of the antenna switching circuit of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of one embodiment. In FIG. 1, the same parts as in FIG. 2 will be described with the same reference numerals.

The antenna switching device 1 is connected to the control device 10 by a control output line 5, and switches the output signal 4 to the television receiver between the video tape recorder playback signal 2 and the external antenna input signal 3 based on the input from the control output line 5. It is a device.

The control device 10 is composed of a controller 6 and a control switch 11, and switches the control switch 11 with the input of the antenna changeover switch 8.
The signal is output to the antenna switching device 1, and the status display device 12 is controlled by the status input.

The forced through switch 9 is connected to the control output line 5, and is used to force the output signal 4 of the antenna switching device 1 to the television receiver to become the external antenna input signal 3 regardless of the input to the antenna switching switch 8, or By inputting the changeover switch 8, it is possible to switch the output signal 4 to the television receiver between the video tape recorder playback signal 2 and the external antenna input signal 3.

Further, the status display device 12 displays whether the output signal 4 to the television receiver is a video tape recorder playback signal or an external antenna input signal.

Note that the control output line 5 is connected to a power source E via a resistor R.

Next, the operation of the antenna switching circuit of the present invention will be explained. First, the case where the forced through switch 9 is off will be explained.

Depending on the input to the antenna changeover switch 8, the control output 7 of the controller 6 turns the control switch 11 on and off. When this control switch 11 is turned on, "L" is input to the antenna switching device 1, and the output signal 4 to the television receiver is output.
becomes external antenna input signal 3.

Furthermore, when the control switch 11 is turned off, the "H" level is input to the antenna switching device 1, and the output signal 4 to the television receiver becomes a video tape recorder playback signal.

Next, a case where the forced through switch 9 is on will be explained. Even if the control switch 11 is turned on or off by the control output 7 of the controller 6 in response to the input of the antenna changeover switch 8, the antenna changeover device 1 is always inputted with the "L" level, and the signal is not transmitted to the television receiver. The output signal 4 becomes the external antenna input signal 3.

Note that the status display device 12 detects the current status of the antenna switching device 1 based on the status of the status input 13 to the controller 6, and the controller 6 performs control display.

In this way, the controller 6 can simply display the information according to the state of the state input 13, and there is no need to consider the states of the antenna changeover switch 8 and the forced through switch 9.

Further, in the above embodiments, the case of a video tape recorder has been described, but the present invention may be applied to other video playback devices such as a video disk player, and the same effects as in the above embodiments can be obtained.

[Effect of idea]

As explained above, this invention connects the forced through switch to the control output line, so
The number of input/output terminals of the control device can be reduced, making it less expensive. Also, the output to the status display can be determined based only on the status input, and the controller itself can be made inexpensive.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of the antenna switching circuit of the present invention, and FIG. 2 is a block diagram of a conventional antenna switching circuit for a video tape recorder. 1... Antenna switching device, 5... Control output line,
6... Controller, 8... Antenna changeover switch, 9... Forced through switch, 10... Control device, 11... Control switch, 12... Status display device. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Claims] 1. An antenna switching device that selects either a video playback signal or an external antenna signal and outputs it to a television receiver, and an antenna switching device that is connected via a control output line to control this antenna switching device and that is connected to the control output line. a control device for detecting the state; an antenna changeover switch for providing input to the control device for switching the state of the control output line; and an antenna changeover switch for keeping the state of the control output line constant regardless of the switching operation of the antenna changeover switch. An antenna switching circuit comprising: a forced switch connected to the control output line to keep the control output line constant; and a status display device that displays the status of the control output line when the control unit detects the status of the control output line.