JPS62207077A - Television monitor device - Google Patents

Abstract

PURPOSE:To automatically display a monitor signal in a television receiver by modulating an external monitor signal with the intermediate frequency of the television receiver, and supplying the output of the said modulation by switching and controlling between the said output and the intermediate-frequency output of television. CONSTITUTION:When a video signal is outputted from an external video source 30, a video detecting circuit 44 outputs a switching-switch signal to a switcher 40 in order to switch the television receiver circuit 10 into monitoring in accordance with the output of a monitor signal, and automatically changes the switcher 40 from its ordinary broadcasting signal input terminal 40a to the monitor input terminal 40b. Therefore, once the source 30 starts operation, the broadcasting signal is no longer supplied to the circuit 10, and the signal from the terminal 40b is displayed on the television screen.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a television monitor device, and particularly to an improvement in a receiving circuit unit that video modulates a monitor signal.

[Prior Art] Television receivers are normally used for receiving broadcast waves, but as various video sources have diversified in recent years, television receivers have become used not only for simply receiving broadcast waves but also as monitors. cases are increasing markedly.

The video source may be, for example, a video tape recorder,
Television cameras, cable televisions, video game consoles, and the like are known, and a general home television receiver must selectively receive monitor signals from these diversified video sources to ensure reliable reception.

[Problems to be Solved by the Invention] As is well known, since television receivers mainly receive broadcast waves, their input section handles signals modulated with high-frequency carrier waves. Monitor signals other than broadcast radio waves are also once modulated at a predetermined carrier frequency and then supplied to the monitor input terminal of the television receiver.

The frequency of the carrier wave of the broadcast radio waves is set to a different value for each broadcast station, and is divided into designated channels.

Therefore, in the past, when a television receiver was used as a monitor device, the monitor signal from the outside was received using an empty channel that was not used in normal broadcast radio waves, and as a result, the monitor signal was transmitted to the -H video modulation circuit. For example, depending on the region, the signal is modulated using a carrier frequency of two channels or one channel, which is an empty channel.

However, in such conventional devices, the monitor signal supplied from the outside is only received on a designated vacant channel, and as a result, it is difficult to switch the TV receiver from normal broadcast wave reception to monitor reception. I had to switch the TV channel to the set monitor channel.

Therefore, in the conventional device, this channel switching is troublesome, and each time the channel is switched, an unpleasant noise image is generated on the screen, which is inconvenient to handle.

In addition, in recent years, monitoring devices have been incorporated into security systems for home or business use, and systems have been put into practical use that image visitors at the entrance using a television camera and display this image on a television screen each time they visit. In such a case,
Each time there is a visitor, the user has to take the trouble of switching the TV channel to the one for monitoring.

The present invention has been made in view of the above-mentioned conventional problems, and its purpose is to automatically transfer externally supplied monitor signals to the TV without the need for channel switching when a television receiver is used as a monitor device. An object of the present invention is to provide an improved television monitor device for displaying images on a receiver.

[Means for Solving the Problems] In order to achieve the above object, the present invention modulates an external monitor signal using an intermediate frequency (IF) of a television receiver, and combines this video modulation output with the television receiver circuit. The intermediate frequency output is switched and controlled by a switch, and when the television receiver is switched from normal broadcast wave reception or non-receiving state to monitor reception, the video modulation output modulated at the intermediate frequency is supplied to the television circuit by the switch. It is characterized by

In television reception, the carrier frequency differs for each channel, but the intermediate frequency processed in the tuner of the television reception circuit is always a constant value, usually 58.75MHz.
z, and extracts this intermediate frequency output from the tuner section of the television receiving circuit, and selectively supplies this intermediate frequency output and a video modulation output modulated by the intermediate frequency that is the constant value to the television circuit. As a result, a good monitoring effect can be achieved regardless of the channel position of the television receiver.

[Operation] Therefore, according to the present invention, the user can receive external monitor signals as they are on the current TV receiver, regardless of the channel, by simply switching the desired video source to the TV receiver. This makes it possible to eliminate the conventional troublesome or unpleasant channel switching.

[Embodiments] Hereinafter, preferred embodiments of the present invention will be described based on the drawings.

In FIG. 1, a portion of the television receiver is shown as a television reception circuit 10. As shown in FIG.

This television receiver 10 mainly shows the high frequency part of the entire circuit, and the figure includes a filter 12, a high frequency amplifier 14, a demodulation circuit 16, and an IF filter 18. A signal at a local oscillation frequency is supplied.

Normally, broadcast waves from an antenna 22 are input to the television receiving circuit 10, and the broadcast waves have a carrier frequency fO determined for each broadcasting station. The received signal (fO) that has passed through the high frequency amplifier 14 is demodulated into a signal of intermediate frequency rH by the output of the local oscillator 20 in the demodulation circuit 16. Then, the demodulated signal having this intermediate frequency fH is passed through the IF filter 18.
The signal is supplied to the video and audio processing circuits via the video and audio processing circuits.

The local oscillation frequency supplied to the demodulation circuit 16 is modulated by a channel set by the user, and the local oscillator 20 in the channel setter has a constant value with the currently received carrier frequency fo. A local oscillation frequency fL determined from the intermediate frequency fH is output.

Therefore, as is well known, it is understood that the television receiving circuit 10 processes the input signal at the currently set carrier frequency fO.

However, in the present invention, the intermediate frequency fH
It is important that the value is always constant regardless of the channel.

In the present invention, the external video source 30 includes, for example, a security system television camera 32, a video tape recorder 34, or a television game 36, either in combination or singly; and audio signals are extracted.

A feature of the present invention is that the signal from the video source 30 is modulated in a video modulation circuit 38, and its output is selectively switched to the intermediate frequency output of the television receiving circuit 10 via a switch 40. Further, the modulation frequency of the video modulation circuit 38 is equal to the intermediate frequency fH of the IF oscillator 42, for example 58.7.
This is defined by 5MHz.

Therefore, according to the present invention, although the video signal from the video source 30 is modulated at the intermediate frequency fH, which is a constant value, the broadcast wave signal is also supplied to the switch 40 as an intermediate frequency signal. When receiving a monitor signal, it is possible to obtain a good reception effect regardless of the channel of the television receiver.

Further, in this embodiment, when the external video source 30 outputs its video signal, the video detection circuit 44 causes the video detection circuit 44 to switch the television receiving circuit 10 for monitoring according to the output of this monitor signal. is the switching device 40
outputs a changeover switch signal to automatically switch the changeover switch 40 from the normal broadcast signal input terminal 408 to the monitor input terminal 40b.
Switch to.

Therefore, when the external video source 30 is activated, the broadcast signal is no longer supplied to the television receiving circuit 10, and the signal from the monitor input terminal 40b is displayed on the television screen.

FIG. 2 shows a preferred embodiment of the above-mentioned switch 40, in which input signals at both input terminals 40a and 40b are supplied to PIN diodes 52a and 52b via capacitors 50a and 50b, respectively. The anode of the diode 52 has an inductance 54. It is grounded via a and 54b. Further, the cathodes of both diodes 52 are connected to the input terminal, and one of them is connected to the re-output terminal of the flip-flop 58 via inductances 55a and 56b.
The switching signal from the video detection circuit 44 described above is used as the switching signal.

Further, the connection points between each diode 52 and the inductance 54 are commonly connected via capacitors 60a and 60b, respectively, and the output terminal 40C is connected to the television circuit.

In FIG. 2, when the switching signal from the video detection circuit 44 is supplied to the flip-flop 58, each PIN
The diode 52 is turned on when the flip-flop output is at the rHJ level, and by switching the flip-flop knob 58, either the broadcast signal or the monitor signal from either input terminal 40a or 40b is selectively output to the output terminal 40G. The Rukoto.

As shown in the above embodiments (according to the present invention, the switching between the broadcast signal and the monitor signal is performed at the intermediate frequency stage, so the intermediate frequency remains constant regardless of the channel position of the television receiver. Taking advantage of this fact, it has the advantage that external monitor signals can be well received on any channel without channel switching.

[Effects of the Invention] As described above, according to the present invention, even if the TV channel is at an arbitrary position, the broadcast radio waves and the monitor signal can be switched without any need for channel switching.
It is possible to eliminate the hassle of switching that occurs as a result of using empty channels as in the past.

[Brief explanation of drawings]

FIG. 1 is a main block circuit diagram showing a preferred embodiment of a television monitor device according to the present invention, and FIG. 2 is a circuit diagram showing a preferred embodiment of a switch in FIG. 1. 10...TV receiving circuit 30...External video source 38...Video modulation circuit 40...Turn off t-! I device fH... Intermediate frequency.

Claims (1)

[Claims] (1) In a television monitor device capable of switching between broadcast radio waves and an external monitor signal, a video modulation circuit modulates the monitor signal at an IF frequency and supplies it to the monitor input terminal, and an IF between the output of the video modulation circuit and the television reception circuit. A switching device that switches the frequency output and outputs it to the television circuit,
A television monitor device characterized in that a monitor signal can be received as is on the current channel of a television receiver.