JPH0391389A - Television monitor system - Google Patents

Abstract

PURPOSE:To prevent the state of nothing displayed on a television monitor unit by detecting a terminal voltage being at a high voltage when a television camera unit connecting terminal in the open state exists to control a switching means. CONSTITUTION:When a switching means SW connects to a terminal T1, power is supplied from a television monitor unit 4a to a television camera unit 1a with a constant current, a video signal is sent from the camera unit 1a to the monitor unit 4a and sent to a television monitor 4b through a buffer amplifier 21. The video image of the camera unit 1a is displayed on both monitor units 4a, 4b in this way. Moreover, power sent from the monitor unit 4b with a constant current is absorbed by a dummy load circuit 22. When the switching means SW is thrown from the position of the terminal T1 to a terminal T2, the constant current supply from a constant current circuit of the monitor unit 4a is not available and a terminal voltage is higher than that of constant current supply. When the high voltage is detected by a terminal voltage detection circuit 23b, the switching means SW is switched so that a terminal T3 and the television monitor unit are immediately connected. Thus, the state of nothing displayed on the monitor units 4a, 4b is not continued.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] 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 television camera unit 1 and one television monitor unit 4 are connected via a transmission line 3.

The television camera unit 1 separates a television camera 11 that photographs the surveillance area, a video signal transmission circuit 12 that transmits the video signal obtained by the television camera 11, and electric power sent as a constant current from the television monitor unit 4. power supply separation circuit 1 that supplies power to the television camera 11
3. The television monitor unit 4 includes a television monitor 41, a video signal receiving circuit 42 that receives a video signal and transmits it to the television monitor 41, and a constant current circuit 43 that supplies constant current power to the television camera unit 1.

With the above configuration, the TV monitor unit 4 supplies power for the TV camera with a constant current, and the TV camera unit 1 separates this constant current and uses it as power for the TV camera to send out a video signal. , the video signal is displayed on the television 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. In this system, power for three TV cameras) 1a, lb, lc, and 2
It is equipped with two TV monitor units) 4a and 4b.
These are switched and connected via a relay adapter 2. In the relay adapter 2, Tl, T2 . T3 is a terminal for connecting a television camera unit, and each television camera unit la.

Transmission lines 3 connected to 1b and 1c are respectively connected. T4. T5 is a terminal for connecting the television monitor unit, and the transmission line 3 connected to each television monitor unit 4a, 4b is connected thereto. SW is a switching means for switching the connection state between the television camera units 1a, 1b, 1c and the television monitor units 4a, 4b, and 21 is a means for receiving a video signal transmitted from the television camera unit and transmitting it to the television monitor unit 4b. Buffer amplifier for transmission, 22 is TV monitor unit 4
This is a pseudo load circuit that absorbs the constant current sent from b.

The operation of this system will be explained below. The switching means SW sequentially switches the connection state from terminal T1 to T2, from terminal T2 to T3, and from terminal T3 to T1 every time a predetermined period of time elapses. Now, assuming that the switching means SW is connected to the terminal T1, power is supplied from the television monitor unit 4a to the television camera unit 1a with a constant current, and a video signal is transmitted from the television camera unit 1a to the television monitor unit 4a. At the same time, it is also transmitted to the television monitor 4b through the buffer amplifier 21. In this way, the image of the television camera unit 1a is displayed on both the television monitor units 4a and 4b. Furthermore, the electric power sent out as a constant current from the television monitor unit 4b is absorbed by the pseudo load circuit 22.

Next, when a certain period of time passes and the switching means SW switches from terminal T1 to T2 and from terminal T2 to T3, the images from the television camera units lb and lc are sequentially displayed on both the television monitor units 4a and 4b. will be displayed on the screen.

[Problems to be Solved by the Invention] In the conventional example shown in FIG.
As shown in the figure. In this case, there arises an inconvenience that nothing is displayed on the television monitor units 4a, 4b while the switching means SW is connected to the terminal T2. Such a problem also occurs when the other terminal T1 or T3 is open.

The above example is an example where the relay adapter 2 has three TV camera unit connection terminals and two TV monitor unit connection terminals, but if the number of terminals increases or decreases, switching It can be considered in the same manner that the number of switching means SW and the number of buffer amplifiers and pseudo load circuits are increased or decreased accordingly. Even in this case, if there is an open terminal to which the television camera unit is not connected, there will be an inconvenience that nothing will be displayed on the television monitor unit while the switching means SW is connected to the open terminal.

The present invention has been made in view of the above points, and an object thereof is to provide a television camera unit of a relay adapter in a television monitor system comprising a plurality of television camera units and at least one television monitor unit. To prevent a situation in which nothing is displayed on a television monitor unit to occur even when a connection terminal has an open terminal.

[Means for Solving the Problems] In order to solve the above problems, the present invention provides a second method for solving the problems described above.
As shown in the figure, power is supplied from the television monitor unit 4 to the television camera unit 1 with a constant current via the transmission line 3, and a video signal is sent from the television camera unit 1 to the television monitor unit 4 via the transmission line 3. As shown in FIG. 1, a television monitor system that transmits a television monitor system includes a relay adapter 2 that switches and connects one of a plurality of television camera units la, lc to at least one television monitor unit 4a. 2 is a TV camera unit connection terminal T1
, T 2 , T 3 and the television monitor unit 4a, and the switching means SW.
terminal-to-terminal voltage detection circuits 23a, 23b, and 23c that detect a higher voltage between the terminals than when transmitting a constant current that occurs when the television monitor unit 4a is connected to the television camera unit connection terminal in an open state; The TV monitor unit 4a is connected to the other TV camera unit connection terminal when the terminal voltage detection circuits 23a, 23b, and 23c detect a voltage between the terminals that is higher than that at the time of sending out the constant current. It is characterized by comprising means for controlling the switching means SW.

Note that in FIG. 1, terminal T2 is in an open state, but
It may be terminal T1 or T3. Further, the number of television camera units and television monitor units is not limited to the example shown in FIG.

[Function] In the example shown in FIG. 1, when the television monitor unit 4a is connected to the open television camera unit connection terminal T2 by the switching means SW, the voltage between the terminals is higher than that when the constant current is sent out. is detected by the inter-terminal voltage detection circuit 23b, the switching means SW is controlled so that the television monitor unit 4a is connected to the other television camera unit connection terminal T3 (or Tl). Therefore, the state in which nothing is displayed on the television monitor unit 4a does not continue. Note that the same can be considered when the television camera unit connection terminal in the open state is T1 or T3.

[Embodiment] FIG. 1 is a circuit diagram of an embodiment of the present invention. A television camera unit 1a1c has the same configuration as the television camera unit 1 shown in FIG. 4a and 4b are television monitor units, which have the same configuration as the television monitor unit 4 shown in FIG. Reference numeral 3 denotes a transmission line, which is composed of, for example, a coaxial cable or a twisted pair wire. 2 is a relay adapter, which has three TV camera unit connection terminals TI, T2. T3 and two TV monitor unit connection terminals T4. It has T5.

Each television camera unit la is connected to terminals Tl and T3.

The transmission lines 3 connected to 1c are respectively connected, but the terminal T2 is in an open state. Terminal T4. Transmission lines 3 connected to each television monitor unit 4a, 4b are connected to T5.

SW is a terminal Tl for connecting a television camera unit.

T2. A switching means for switching the connection state between T3 and the television monitor unit 4a; 21 is a buffer amplifier that receives video signals transmitted from the television camera unit and transmits them to the television monitor unit 4b; and 22 is a buffer amplifier for receiving video signals sent from the television monitor unit 4b. This is a pseudo load circuit that absorbs the constant current that flows.

23a, 23b, and 23c are inter-terminal voltages for detecting a higher voltage between the terminals than when transmitting a constant current, which occurs when the television monitor unit is connected to the terminal for connecting the television camera unit which is in the open state by the switching means SW. It is a detection circuit.

The operation of this system will be explained below. The switching means SW sequentially switches the connection state from terminal T1 to T2, from terminal T2 to T3, and from terminal T3 to T1 every time a predetermined period of time elapses, but the inter-terminal voltage detection circuit 23a , 23b, or 23c detects a voltage between the terminals that is higher than that during constant current transmission, the TV monitor unit is immediately controlled to be connected to the next terminal. Now, assuming that the switching means SW is connected to the terminal T1, power is supplied from the television monitor unit 4a to the television camera unit 1a with a constant current, and a 0 video signal is transmitted from the television camera unit 1a to the television monitor unit 4a. At the same time as being transmitted, buffer amplifier 2
1 and is also transmitted to the television monitor 4b. In this way, the image of the television camera unit 1a is displayed on both the television monitor units 4a and 4b. Further, the electric power sent out as a constant current from the television monitor unit 4b is absorbed by the pseudo load circuit 22.

Next, when the switching means SW switches from terminal T1 to T2 after a certain period of time has passed, since terminal T2 is in an open terminal state with no connection to the television camera unit, a constant current is sent from the constant current circuit of the television monitor unit 4a. cannot be performed, and the voltage between the terminals becomes higher than when sending constant current. When this high voltage is detected by the inter-terminal voltage detection circuit 23b, the switching means SW is immediately switched so that the terminal T3 and the television monitor unit are connected. therefore,
The state in which nothing is displayed on the television monitor units 4a and 4b does not continue.

The above embodiment is an example where the relay adapter has three TV camera unit connection terminals and two TV monitor unit connection terminals, but if the number of these terminals increases or decreases, It can be considered in the same manner that the number of switches of the switching means SW, the number of buffer amplifiers and pseudo load circuits, and the number of inter-terminal voltage detection circuits are increased or decreased accordingly.

[Effects of the Invention] As described above, in the present invention, power is supplied from the television monitor unit to the television camera unit with a constant current through the transmission line, and power is supplied from the television camera unit to the television through the transmission line. A television monitor system that transmits video signals to a monitor unit includes a relay adapter that switches and connects one of a plurality of television camera units to at least one television monitor unit, and a television camera unit in an open state is connected to the relay adapter. Even if there is a connection terminal, it is detected that the terminal is open by detecting a voltage between the terminals that is higher than that when sending out a constant current using a voltage detection circuit between the terminals,
Since the switching means is controlled so that the television monitor unit is connected to the other television camera unit connection terminal, there is an effect that it is possible to eliminate the inconvenience that nothing is displayed on the television monitor unit for a long time.

[Brief explanation 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. 3 is a block circuit diagram of an embodiment of the present invention.
FIG. 4 is a block circuit diagram of a television monitor system equipped with a conventional relay adapter. 1a and 1c are television camera units, 2 is a relay adapter, 3 is a transmission line, 4a and 4b are television monitor units, SW is a switching means, 23a, 23b, and 23c are inter-terminal voltage detection circuits, Tl, T2. T3 is a terminal for connecting a television camera unit.

Claims (1)

[Claims] (1) In a television monitor system in which power is supplied from the television monitor unit to the television camera unit with a constant current via the transmission line, and video signals are transmitted from the television camera unit to the television monitor unit via the transmission line, multiple 1 of the 1 TV camera units
The relay adapter includes a switching means for switching the connection state between the TV camera unit connection terminal and the TV monitor unit, and a switching means for switching the connection state between the TV camera unit connection terminal and the TV monitor unit, and a TV set in the open state by the switching means. A terminal voltage detection circuit detects a voltage between the terminals that is higher than that during constant current transmission that occurs when a TV monitor unit is connected to the camera unit connection terminal, and a terminal voltage detection circuit detects the voltage between the terminals when the constant current is transmitted. and means for controlling the switching means so that the television monitor unit is connected to the other television camera unit connection terminal when a higher voltage between the terminals is detected. .