JPH078038B2 - Tv monitor system - Google Patents

Description

TECHNICAL FIELD The present invention relates to a television monitor system used in a surveillance camera system or the like.

[Prior Art] FIG. 2 shows a schematic configuration of a conventional television monitor system. In this system, one TV camera unit 1 and one TV monitor unit 4 are connected via a transmission line 3. TV camera unit 1
Is a TV camera that separates the electric power sent from the TV monitor unit 4 with a constant current from the TV camera 11 that shoots the surveillance area, the video signal transmission circuit 12 that sends the video signal obtained by the TV camera 11, 11 is provided with a power supply separation circuit 13 which is supplied as a power supply. The TV monitor unit 4 includes a TV monitor 41, a video signal receiving circuit 42 that receives a video signal and transmits the video signal to the TV monitor 41, and a constant current circuit 43 that supplies electric power to the TV camera unit 1 at a constant current.

With the above configuration, the TV monitor unit 4 supplies the TV camera power with a constant current, and the TV camera unit 1 separates the constant current and uses it as the TV camera power to send a video signal. The video signal is displayed on the TV monitor unit 4.

Next, FIG. 3 shows a conventional example of a television monitor system including a plurality of television camera units 1 and television monitor units 4 as described above. This system includes three TV camera units 1a, 1b and 1c and two TV monitor units 4a and 4b, which are switchably connected via a relay adapter 2. In the relay adapter 2, T1, T2, and T3 are terminals for connecting the TV camera units, and the transmission lines 3 connected to the TV camera units 1a, 1b, and 1c are connected thereto. T4 and T5 are terminals for connecting the TV monitor units, to which the transmission lines 3 connected to the TV monitor units 4a and 4b are respectively connected. SW is a switching means for switching the connection state between the TV camera units 1a, 1b, 1c and the TV monitor units 4a, 4b, and 21 is a buffer for receiving the video signal transmitted from the TV camera unit and transmitting it to the TV monitor unit 4b. The amplifier 22 is a pseudo load circuit that absorbs the constant current sent from the TV monitor unit 4b.

The operation of this system will be described below. The switching means SW sequentially switches the connection state from the terminal T1 to T2, from the terminal T2 to T3, and from the terminal T3 to T1 each time a certain fixed time elapses. Now, assuming that the switching means SW is connected to the terminal T1, power is supplied from the TV monitor unit 4a to the TV camera unit 1a at a constant current, and the video signal is transmitted from the TV camera unit 1a to the TV monitor unit 4a. At the same time, it is transmitted to the television monitor 4b through the buffer amplifier 21. In this way
The image of the TV camera unit 1a is displayed on both the TV monitor units 4a and 4b. Also, the electric power sent from the TV monitor unit 4b at a constant current is a pseudo load circuit.
Absorbed by 22. Next, when the switching means SW switches from the terminal T1 to T2 and from the terminal T2 to T3 after a certain period of time, the images from the TV camera units 1b and 1c are sequentially displayed on both the TV monitor units 4a and 4b. Is projected on.

[Problems to be Solved by the Invention] FIG. 4 shows a circuit configuration when the television camera unit 1b is not connected to the terminal T2 in the conventional example shown in FIG. In this case, there is an inconvenience that nothing is displayed on the television monitor units 4a and 4b while the switching means SW is connected to the terminal T2. Such inconvenience is caused by other terminals
It also occurs when T1 or T3 is open.

The above example is an example where the relay adapter 2 has three terminals for connecting the TV camera unit and two terminals for connecting the TV monitor unit, but when the number of terminals increases or decreases, the switching is performed. The same consideration can be made only by changing the number of switching means SW and the number of buffer amplifiers and pseudo load circuits correspondingly. Even in this case, if there is an open terminal to which the TV camera unit is not connected, the switching means
The problem occurs that nothing is displayed on the TV monitor unit while the SW is connected to the open terminal.

In Japanese Patent Laid-Open No. 62-117488, a television camera switching device for switching video signals of a plurality of television cameras is provided with a detection circuit for detecting whether or not the television cameras are connected, and if the television cameras are not connected. , A configuration for selecting the next TV camera is disclosed, but a specific configuration of the TV camera detection circuit, in particular, power is supplied from the TV monitor side to the TV camera side at a constant current via a video signal transmission line. It does not disclose the configuration of the television camera detection circuit utilizing the characteristics of the television monitor system.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a TV camera system of a relay adapter in a TV monitor system including a plurality of TV camera units and at least one TV monitor unit. Even if the connection terminal has an open terminal, it is necessary to prevent the state where nothing is displayed on the TV monitor unit.

[Means for Solving the Problems] In the present invention, in order to solve the above problems, a second
As shown in the figure, electric power is supplied from the TV monitor unit 4 to the TV camera unit 1 via the transmission line 3 at a constant current, and at the same time, a video signal is sent from the TV camera unit 1 to the TV monitor unit 4 via the transmission line 3. As shown in FIG. 1, a television monitor system for transmitting a signal is provided with a relay adapter 2 for switching and connecting one of the plurality of television camera units 1a and 1c to at least one television monitor unit 4a. Two
Is a switching means for switching the connection state between the TV camera unit connection terminals T1, T2, T3 and the TV monitor unit 4a.
SW and an inter-terminal voltage detection circuit that detects an inter-terminal voltage that is higher than the constant current generated when the TV monitor unit 4a is connected to the TV camera unit connection terminal in the open state by the switching means SW. When 23a, 23b, 23c and the inter-terminal voltage detection circuit 23a, 23b, 23c detect a higher inter-terminal voltage than the above-mentioned constant current output, the TV monitor unit is connected to the other TV camera unit connection terminals.
And means for controlling the switching means SW so that 4a is connected.

Although the terminal T2 is open in FIG. 1, it may be the terminal T1 or T3. The number of TV camera units and TV monitor units is not limited to the example shown in FIG.

[Operation] In the example shown in FIG. 1, when the TV monitor unit 4a is connected to the TV camera unit connecting terminal T2 in the open state by the switching means SW, the inter-terminal voltage higher than that during constant current transmission Is detected by the inter-terminal voltage detection circuit 23b, the other TV camera unit connection terminal T3
The switching means SW is controlled so that the television monitor unit 4a is connected to (or T1). Therefore, the state where nothing is displayed on the TV monitor unit 4a does not continue.
The terminal for connecting the TV camera unit in the open state is T1.
Alternatively, it can be similarly considered when T3.

[Embodiment] FIG. 1 is a circuit diagram of an embodiment of the present invention. Reference numerals 1a and 1c denote television camera units, which have the same configuration as the television camera unit 1 shown in FIG. Reference numerals 4a and 4b denote TV monitor units, which have the same configuration as the TV monitor unit 4 shown in FIG. 3 is a transmission line,
For example, it is composed of a coaxial cable or a twisted pair wire.
A relay adapter 2 has three TV camera unit connecting terminals T1, T2, T3 and two TV monitor unit connecting terminals T4, T5. The transmission lines 3 connected to the television camera units 1a and 1c are connected to the terminals T1 and T3, respectively, but the terminal T2 is in an open state. The transmission lines 3 connected to the TV monitor units 4a and 4b are connected to the terminals T4 and T5, respectively. SW is a switching means for switching the connection state between the TV camera unit connecting terminals T1, T2, T3 and the TV monitor unit 4a, and 21 is for receiving the video signal transmitted from the TV camera unit and transmitting it to the TV monitor unit 4b. Buffer amplifier, 22
Is a pseudo load circuit that absorbs a constant current sent from the TV monitor unit 4b. 23a, 23b, and 23c are terminal voltages for detecting a high terminal voltage by sending a constant current generated when the TV monitor unit is connected to the terminal for connecting the TV camera unit in the open state by the switching means SW. It is a detection circuit.

The operation of this system will be described below. The switching means SW sequentially switches the connection state from the terminal T1 to T2, from the terminal T2 to T3, and from the terminal T3 to T1 each time a certain fixed time elapses. 23a, 23b, 23c
When any one of them detects a voltage between terminals that is higher than that during constant current transmission, it is immediately controlled to connect the TV monitor unit to the next terminal. Now, the switching means SW is terminal T1
Connected to the TV monitor unit 4a
Power is supplied from the TV camera unit 1a to the TV monitor unit 4a at a constant current, and the video signal is transmitted from the TV camera unit 1a to the TV monitor unit 4a and also to the TV monitor 4b through the buffer amplifier 21. In this way, the image of the TV camera unit 1a is displayed on both the TV monitor units 4a and 4b. Further, the electric power sent from the television monitor unit 4b at a constant current is absorbed by the pseudo load circuit 22.

Next, when the switching means SW is switched from the terminal T1 to the terminal T2 after a certain period of time, the terminal T2 is in an open terminal state in which the TV camera unit is not connected. Therefore, the TV monitor unit 4a
The constant current circuit cannot send a constant current, and the inter-terminal voltage becomes higher than that at the time of sending the constant current. When this high voltage is detected by the inter-terminal voltage detection circuit 23b, the terminal T
The switching means SW is switched so that 3 and the TV monitor unit are connected. Therefore, the state in which nothing is displayed on the TV monitor units 4a and 4b does not continue.

The above embodiment is an example in which the relay adapter has three TV camera unit connecting terminals and two TV monitor unit connecting terminals, but when the number of these terminals increases or decreases. It can be considered in a similar manner only by changing the number of switching means SW, the number of buffer amplifiers and similar load circuits, and the number of terminal voltage detection circuits correspondingly.

[Advantages of the Invention] According to the present invention, as described above, electric power is supplied from the TV monitor unit to the TV camera unit at a constant current via the transmission line, and the TV camera unit sends the TV to the TV line via the transmission line. In a TV monitor system for transmitting a video signal to a monitor unit, a relay adapter for switching and connecting one of a plurality of TV camera units to at least one TV monitor unit is provided, and this TV adapter unit is in an open state. Even if there is a connection terminal, the fact that the terminal is in the open state is detected by detecting the voltage between the terminals, which is higher than that during constant current transmission, by the terminal voltage detection circuit,
Since the switching means is controlled so that the TV monitor unit is connected to the other TV camera unit connection terminal, there is an effect that it is possible to eliminate the inconvenience that nothing is displayed on the TV monitor unit.

[Brief description of drawings]

FIG. 1 is a block circuit diagram of an embodiment of the present invention, FIG. 2 is a block circuit diagram of a conventional television monitor system, and FIG.
FIG. 4 and FIG. 4 are block circuit diagrams of a television monitor system including a conventional relay adapter. 1a and 1c are TV camera units, 2 is a relay adapter,
3 is a transmission line, 4a and 4b are TV monitor units, SW is a switching means, 23a, 23b and 23c are terminal voltage detection circuits, T1, T2 and T3
Is a terminal for connecting a TV camera unit.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Keiichi Mizuguchi, 1048, Kadoma, Kadoma, Osaka Prefecture, Matsushita Electric Works, Ltd. (72) Kazuhito Kaburaki, 1048, Kadoma, Kadoma, Osaka, Matsushita Electric Works, Ltd. ) Inventor Muneo Suzuki 1048, Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Works Co., Ltd.

Claims (1)

[Claims] 1. A television monitor system for supplying electric power from a television monitor unit to a television camera unit at a constant current through a transmission line and transmitting a video signal from the television camera unit to the television monitor unit through the transmission line. A relay adapter for switching and connecting one of the plurality of TV camera units to at least one TV monitor unit, and the relay adapter includes switching means for switching a connection state between the TV camera unit connection terminal and the TV monitor unit. And a terminal-to-terminal voltage detection circuit that detects a terminal-to-terminal voltage that is higher than the constant current that is generated when the TV monitor unit is connected to the TV camera unit connection terminal in the open state by the switching means, and a terminal. Since the constant current is sent by the inter-voltage detection circuit Television monitoring system characterized in that it comprises a means for controlling the switching means so TV monitor unit is connected to a terminal other TV camera unit connected when the terminal voltage of the high voltage is detected.