JPH0520060Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Field of Application] This invention relates to an RF modulator device for video signals, and is particularly applicable to those having a switching function that can switch between a TV antenna output and the output of a VTR, etc.

[Summary of the idea]

A DC voltage is superimposed on the RF output of the RF modulator unit and transmitted to a remote switch via a cable, and this DC voltage is used as a switching signal.
The received signal from the TV antenna is switched to the modulator output so that it can be output to the monitor TV,
This allows remote switching of RF signals by turning on and off the power of video equipment connected to the RF modulator unit.

[Conventional technology]

Figure 5 shows a connection example of a conventional RF switch type TV monitor system. For example, VTR1 is a portable type with a video camera,
Outputs the NTSC video signal as a playback signal.
The RF modulator unit 3 is of a type that is directly attached to the output terminal connector of the VTR 1 without using a cable. The RF output of the RF modulator unit 3 and the received signal of the TV antenna 5 are switched by an RF changeover switch 11 called an antenna switch and supplied to the monitor TV 6.

The RF changeover switch 11 is mechanical (manually operated), and is usually placed near the operation panel of the monitor TV 6, and connects each coaxial cable 12a to 12c connected to the TV antenna 5, RF modulator unit 3, and monitor TV 6. Wire and use.

[Problem that the invention attempts to solve]

In order to monitor TV broadcast video and VTR playback video, it is necessary to switch the RF changeover switch 11 each time, which is cumbersome. Also, the coaxial cable 12a
~12c needs to be routed, which is inconvenient to handle, and if the coaxial cable from the indoor TV antenna is short, the installation location of the RF switch 11 cannot be selected to be convenient for operation. There is also.

In view of this problem, the present invention aims to eliminate the troublesome switching operation and the inconvenience associated with cable wiring.

[Means for solving problems]

The RF modulator device of the present invention is an RF modulator device that is connected to a portable video device (VTR 1) that outputs a video signal and outputs a conveying RF signal to a monitor receiver 6, and has an output terminal of the portable video device. an RF modulator unit 3, which is provided with a plug or receptacle that can be directly attached to the portable video device, and receives the supply of video signals and power supply voltage when the portable video device is operated;
One end is connected to the above RF modulator unit,
It has one coaxial RF cable 7 for deriving the RF output of the RF modulator unit, a connection terminal for the TV antenna cable 12a and a connection terminal for the monitor receiver cable 12c, and the other end of the RF cable is and a changeover switch unit 4 that is connected to the RF cable and switches between the RF signal supplied via the RF cable and the received signal from the TV antenna 5 and outputs it to the monitor receiver, and the changeover switch unit The DC voltage superimposed on the RF signal transmitted via the cable is used as a switching signal to switch the above from the received signal side of the TV antenna.
It is characterized by being configured so that it can be switched to the RF signal side.

[Effect]

The two RF inputs (antenna output and RF modulator output) can be switched by turning on and off the power of the connected video equipment. RF modulator unit 3
When power is no longer supplied to the TV antenna, the switch automatically switches to the TV antenna side. Since it is possible to remotely control the switch connected via the RF cable, the switch can be placed freely.

〔Example〕

FIG. 1 shows a block diagram of an RF modulator device to which the present invention is applied. RF modulator device 2
is the RF modulator unit 3 and its output.
An electronic changeover switch unit 4 (hereinafter simply referred to as changeover switch 4) is provided for switching the received signal from the TV antenna 5. RF modulator unit 3 has connector 3a (plug and receptacle)
It can be directly connected to VTR1 via.
The RF modulator unit 3 and electronic changeover switch 4 are connected by an RF coaxial cable 7.

The output of VTR1 consists of, for example, an NTSC video signal and an audio signal, which together with the power supply voltage V _CC
It is supplied to the RF modulator unit 3. RF modulator unit 3 monitors the input signal
The signal is converted into the carrier frequency of the first channel or the second channel of 6 and is output to the switching terminal 4a of the electronic switching switch 4. On the other hand, the output (received signal) of the TV antenna 5 is applied to the switching terminal 4b of the electronic switching switch 4.

A predetermined DC voltage E is superimposed on the RF signal output from the RF modulator unit 3, as shown in FIG. This DC voltage is changed to electronic selector switch 4.
Used as a switching control signal. When the RF modulator unit 3 is connected to the VTR 1 and the power of the VTR 1 is turned on as shown in Fig. 1, the DC voltage E is supplied together with the RF signal to the electronic changeover switch 4, and the changeover contact 4c is connected to the terminal. 4a side, the output of RF modulator unit 3, that is,
The reproduced signal of the VTR 1 is selected by the changeover switch 4 and output to the monitor TV 6.

Turn off the power to VTR1 or turn off unit 3 to the VTR.
1, the DC voltage E disappears and the switching contact 4c of the electronic switching switch 4 automatically returns to the switching terminal 4b side, that is, the output side of the TV antenna 5.

Therefore, to monitor the playback video of VTR1,
To monitor TV broadcast images, all you need to do is turn on the power of VTR1 and turn off the power of VTR1.
Note that if unit 2 is not connected to VTR 1,
The TV antenna 5 and the monitor TV 6 are unconditionally connected directly.

Since the electronic changeover switch 4 can be remotely controlled by turning on and off the power of the VTR 1 in this way, the electronic changeover switch 4 can be placed behind the TV monitor 6, for example. In this case, the coaxial cable 12a of the output of the TV antenna 5
The coaxial cable 12c output from the electronic changeover switch 4 is wired to the antenna 5 and the monitor TV 6, respectively, and the RF modulator unit 3 is attached to the connector of the VTR 1. In the state of the product sold as an adapter unit, the RF modulator unit 3 and the electronic changeover switch 4 are already connected by a coaxial cable 7 of 1 to 2 m.

Figure 3 shows the electronic changeover switch 4 in Figure 1.
An example of the configuration is shown below. The received signal from the TV antenna 5 is normally sent to the monitor TV 6 through capacitors C1 and C2.
is derived. When the DC voltage E is supplied from the RF modulator unit 3 to the changeover switch 4, the base current flows to the transistor Q via the resistor R1, turning this transistor on, and the connection point between the capacitors C1 and C2 is grounded. be done. On the other hand, voltage E is supplied to diode D1, and a current that turns on this diode flows through coil L1 and resistor R2. The RF modulator unit 3 thus supplied to the anode of the diode D1
The output is led out to the monitor TV6 through the cathode of the diode D1 or the capacitor C3.

It is conceivable to incorporate the RF modulator circuit 8 into the electronic changeover switch 4 to form one RF unit 9, as in the reference embodiment shown in FIG. In this case, switch 4 switches the power supply voltage V _CC supplied from VTR 1 to modulator circuit 8.
By using the switching control signal as shown in FIG. 1, remote control similar to that shown in FIG. 1 is possible, and the arrangement of the RF unit 9 can be freely selected.

However, the relatively long connection cable 10 between the VTR 1 and the RF unit 9 has a five-core configuration consisting of a video shield line, an audio shield line, and a V _CC line, which is expensive.

On the other hand, in the embodiment shown in FIG. 1, simply by extending one RF coaxial cable 7, the changeover switch 4 can be installed at any position, resulting in a very low cost. Furthermore, since the cable wire diameter is also smaller, cable wiring is easier.

[Effect of idea]

As mentioned above, in this invention, even when the power is supplied from the video equipment, the changeover switch is switched from the received signal of the TV antenna to the output side of the RF modulator, so that the monitor TV only has one input terminal. Even if it is necessary to switch between the TV antenna and the signal from a video device such as a VCR, there is no need to switch at all, and you can monitor the video device output by turning on the power to the video device. By turning off, you can monitor the broadcast reception waves from the TV antenna.

In addition, there is no need to have an RF switch at hand or in a position where it can be operated, and the RF modulator unit can be attached directly to portable video equipment, and the RF cable (coaxial Since the devices are connected only by cables, the cable wiring between the devices is very simple, and the RF modulator device can be manufactured at a lower cost.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of an RF modulator device showing an embodiment of the present invention, Fig. 2 is a waveform diagram of the transmitted RF modulator output, Fig. 3 is a circuit diagram showing an example of an electronic changeover switch, and Fig. 4 5 is a circuit diagram as a reference example in which an RF modulator and a changeover switch are integrated, and FIG. 5 is a diagram showing an example of a conventional RF changeover switch type device connection. In addition, in the symbols used in the drawings, 1... VTR,
2...RF modulator device, 3...RF modulator unit, 4...electronic changeover switch, 5...
...TV antenna, 6...connector, 7...coaxial cable.

Claims (1)

[Claim for Utility Model Registration] An RF modulator device that is connected to a portable video device that outputs a video signal and derives a carrier RF signal to a monitor receiver, which is directly attached to the output terminal of the portable video device. an RF modulator unit which is provided with a plug or receptacle that can be connected to the portable video equipment and receives a video signal and a power supply voltage when the portable video equipment is in operation; It has one coaxial RF cable that derives the RF output of and a switch unit that switches between the supplied RF signal and the received signal from the TV antenna and outputs the signal to the monitor receiver, and the switch unit superimposes the RF signal on the RF signal transmitted via the RF cable. An RF modulator device configured to switch from the received signal side of the TV antenna to the RF signal side using the DC voltage as a switching signal.