JP2605702B2 - RF Modulator Unit - Google Patents

Description

The present invention relates to an RF modulator unit for a video signal, and more particularly, to an RF modulator unit having a switching function capable of switching between a TV antenna output and an output of a VTR or the like. Things.

[Summary of the Invention]

The received signal from the TV antenna is converted to the RF modulator circuit by the power supply voltage supplied from the outside together with the video signal.
RF that can be switched to RF signal output and derived to a monitor
A modulator unit that enables switching of RF output by turning on and off the power of a video device to be connected.

[Conventional technology]

FIG. 5 shows a connection example of a conventional RF changeover switch type TV monitor system. The VTR 1 is, for example, a portable type with a video camera, and outputs an NTSC video signal as a reproduction signal. The RF modulator unit 10 is of a type that is directly attached to the output terminal connector of the VTR 1 without using a cable. RF of this RF modulator unit 10
The output and the received signal of the TV antenna 5 are switched by an RF switch 11 called an antenna switch and supplied to the monitor TV 6.

The RF changeover switch 11 is of a mechanical type (manual operation type), and is usually placed near the operation panel of the monitor TV 6 to wire the TV antenna 5, the RF modulator unit 10 and the coaxial cables 12a to 12c connected to the monitor TV 6. Used.

[Problems to be solved by the invention]

In order to monitor the TV broadcast video and the VTR playback video, it is necessary to switch the RF switch 11 each time, which is troublesome. In addition, it is necessary to route coaxial cables 12a to 12c,
In addition to being inconvenient to handle, if the coaxial cable from the TV antenna in the room is short, there is a problem that the installation location of the RF switch 11 cannot be selected as a convenient location for operation.

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

[Means for solving the problem]

The RF modulator unit of the present invention is connected to a video device 1 that outputs a video signal and an operation power supply voltage of an external RF modulator, and derives a carrier RF signal to a monitor receiver 6. An RF modulator circuit 3 for converting a video signal output into a carrier RF signal of a predetermined channel; an RF signal output from the RF modulator circuit 3 and a TV
Monitor receiver 6 by switching between the received signal from antenna 5 and
, A video signal output of the video equipment and a receiving signal of the TV antenna, and an output terminal of the changeover switch. Changeover switch 4, the output RF signal of the RF modulator circuit 3 is supplied to the anode side, the cathode side includes a diode D ₁ connected to the output terminal is grounded via an inductance, RF modulator circuit from the video equipment 1 An electronic switch configured to switch an operation power supply voltage supplied to the TV antenna 3 as a control signal, and outputs a carrier RF signal when the video equipment 1 is in an operating state; Switching control of the electronic switch is performed so as to output a reception signal.

[Action]

Two RF with power on / off of connected video equipment
Switches input (antenna output and RF modulator output). When the power supply to the RF modulator unit is lost, the switch automatically switches to the TV antenna side.

〔Example〕

FIG. 1 is a block diagram showing an RF modulator unit to which the present invention is applied. The RF modulator unit 2 includes an RF modulator 3 and an electronic changeover switch 4 for switching an output of the RF modulator 3 and a signal received from the TV antenna 5. The unit 2 can be directly connected to the VTR 1 via the connector 7 (plug and receptacle) as shown in the connection example of FIG.

The output of VTR1 comprises, for example, an NTSC video signal and an audio signal, which are supplied to the RF modulator 3 together with the power supply voltage _Vcc . The RF modulator 3 monitors the input signal on the monitor TV
6 is converted into the carrier frequency of the first channel or the second channel and is led out to the switching terminal 4a of the electronic changeover switch 4. On the other hand, the output (received signal) of the TV antenna 5 is supplied to the switching terminal 4b of the electronic changeover switch 4.

Power supply voltage V _cc which is supplied to an RF modulator unit 2 from the VTR1 is made to the switching control signal of the electronic changeover switch 4. When the unit 2 is connected to the VTR 1 and the power supply of the VTR 1 is turned on, the power supply voltage _Vcc is supplied to the electronic changeover switch 4, and the changeover contact 4c is switched to the terminal 4a side, and the output of the RF modulator 3 is changed. That is, the reproduced signal of the VTR 1 is selected by the changeover switch 4 and led out to the monitor TV 6.

When the power of the VTR 1 is turned off or the unit 2 is disconnected from the VTR 1, the power supply voltage _Vcc is lost, and the electronic changeover switch 4
The switching contact 4c 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, the power of VTR1 should be turned on, and to monitor the TV broadcast video, the power of VTR1 should be turned off. If the unit 2 is not connected to the VTR 1, the TV antenna 5 and the monitor TV 6 are directly connected unconditionally.

FIG. 3 shows another example of connection. In this example, the RF modulator unit 2 has an input cable 8 and can be connected to the VTR 1 via a connector at the end thereof. The rest is the same as the embodiment of FIG. In this modification, it is necessary to use a multi-core cable including the video signal, the audio signal, the power supply voltage _Vcc, and the ground line as the input cable 8, but the degree of freedom in the installation position of the unit 2 increases. That is, the RF modulator unit 2 can be placed, for example, behind the monitor TV6. In this case, if the coaxial cable 12a of the output of the TV antenna 5 and the coaxial cable 12c of the output of the unit 2 are wired and the input cable 8 of the unit 2 is connected to the output of the VTR 1, the unit 2 does not need to be brought out to the front. By turning on / off the power of the VTR 1, it is possible to switch between the TV broadcast video and the VTR playback video for monitoring.

FIG. 4 shows an example of the configuration of the electronic changeover switch 4 in FIG. The received signal of TV antenna 5 is usually a capacitor
It is led to the monitor TV6 through C1 and C2. When the power supply voltage _Vcc is supplied from the VTR1 to the RF modulator unit 2, a base current flows to the transistor Q via the resistor R1, and this transistor turns on, and the capacitor C1
The connection point with C2 is grounded. On the other hand, the voltage _Vcc is supplied to the diode D1 via the resistor R2, and a current for turning on the diode flows through the coil L1. Therefore, the output of the RF modulator 3 supplied to the cathode of the diode D1 is led out from the anode of the diode D1 to the monitor TV through the capacitor C3.

〔The invention's effect〕

As described above, according to the present invention, the changeover switch is switched from the reception signal of the TV antenna to the output side of the RF modulator circuit by the power supply from the video equipment, so that the monitor TV has one input terminal. Even if it is necessary to switch between a TV antenna and a signal from a video device such as a VTR, a switching operation using a manual switch is completely unnecessary, and if the video device is turned on, the output of the video device can be monitored.
If the power is turned off, the broadcast reception wave from the TV antenna can be monitored.

In addition, since it is not necessary to place the RF changeover switch at a hand or at an operable position, cable wiring between devices can be simplified.

[Brief description of the drawings]

FIG. 1 is a block diagram of an RF modulator unit showing one embodiment of the present invention, FIG. 2 is a diagram showing one connection example of wiring between devices, FIG. 3 is a diagram showing another connection example, FIG. FIG. 5 is a circuit diagram showing an example of an electronic changeover switch, and FIG. 5 is a diagram showing an example of connection between devices of a conventional RF changeover type. Reference numerals used in the drawings are: 1. VTR 2. RF modulator unit 3. RF modulator 4. Electronic changeover switch 5. TV antenna 6. Monitor TV.

Claims (1)

(57) [Claims] An RF modulator unit connected to a video device for outputting a video signal and an operating power supply voltage of an external RF modulator, and for leading a carrier RF signal to a monitor receiver, wherein the video signal output of the video device is provided. An RF modulator circuit that converts the RF signal into a carrier RF signal of a predetermined channel, a changeover switch that switches between an RF signal output from the RF modulator circuit and a reception signal from a TV antenna and guides the signal to a monitor receiver, Each of the input terminals of a video signal output and a reception signal of a TV antenna and an output terminal of the changeover switch, the changeover switch is supplied with an output RF signal of the RF modulator circuit on an anode side, and has an anode on an anode side via an inductance. The video modulator includes a diode connected to the output terminal and the RF modulator circuit from the video device. It comprises an electronic switch capable of switching the operation power supply voltage supplied to the control signal as a control signal, and outputs the transport RF signal when the video device is in an operating state,
An RF modulator unit, wherein switching control of the electronic switch is performed so as to output a reception signal of the TV antenna when the video device is inoperative.