JPS6125274B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ITV system that monitors railway stations, traffic in tunnels, etc., for example.

Conventional ITV systems connect ITV cameras and monitor TVs in one-to-one correspondence through a dedicated image transmission line, or, as shown in Figure 1, switch unit C of monitoring station B is activated by commands from control unit A. A large number of ITV cameras D can be freely switched through a switching operation, thereby transmitting images between a desired ITV camera D and a desired monitor television E. However, according to these, ITV Camera D and Monitor TV E
The longer the transmission line F that connects the monitoring station, the greater the transmission loss.
If image signals of the same level are transmitted from the ITV camera D, there will be variations in the level of the image signals received by the monitoring station B, and as a result, there is a problem that the image accuracy of the monitor TV E will not be uniform.

To overcome this difficulty, the output level of each ITV camera D can be changed, but the output of each ITV camera D must be kept constant in consideration of compatibility.

Therefore, as shown in FIG. 2, the control unit A installed in the monitoring station B switches the switching unit H installed in each terminal station G to connect the image transmission line F corresponding to each ITV camera D and each monitor TV E. Connections can be switched freely,
This makes it possible to transmit images between the desired ITV camera D and the desired monitor television E, and
It is conceivable to insert a pseudo line J in front of the receiving device I of the monitoring station B.

However, if the pseudo line J is inserted directly into the image transmission line E as shown in Figure 2, the level of the image signal transmitted from the ITV camera D via the transmitting device K will be different in front of the receiving device I. At B, it is necessary to separately detect which ITV camera D the signal being received comes from, and then set or switch the pseudo line J to obtain an appropriate signal level.

Also, according to this, the signal level of each image transmission line F in the cable differs depending on from which point the signal is inserted into the image transmission line F. Another drawback is that the crosstalk noise to the image transmission line F, through which weak-level signals are transmitted, is greater than in the conventional ITV system.

The present invention solves these various difficulties, and if this is described in detail based on FIG. 3, the monitoring station 1
The monitor television 2 and the ITV camera 4 of each terminal station 3 are connected by an image transmission line 5, and each terminal station 3 is provided with a transmission line switching device 6 for switching the connection between the ITV camera 4 and the image transmission line 5, This switching device 6 is switched in response to a command from a control unit 7 provided in the monitoring station 1 to enable image transmission between a desired monitor television 2 and a desired ITV camera 4, and also connects each ITV camera 4 to a transmission line. A pseudo line 8 is inserted between the switching device 6 and the switching device 6.

The pseudo length of each pseudo line 8 is the same as that of the monitoring station 1.
Set to the difference between the transmission line length from the farthest ITV camera 4 to the transmission line length from the monitoring station 1 to each of the other ITV cameras 4.

The control unit 7 not only controls switching of the transmission line switching device 6, but also controls the monitor mode and each ITV.
It is preferable to also be able to control determination of monitoring requests from the cameras 4, various instructions to each ITV camera 4, and the like.

As described above, the present invention inserts a pseudo line 8 between each ITV camera 4 and the transmission line switching device 6, and furthermore, the pseudo length of the pseudo line 8 is extended from the monitoring station 1 to the farthest ITV camera 4. transmission line length and monitoring station 1
Since the transmission line length from each ITV camera 4 to each other ITV camera 4 is set to the difference between The image signals transmitted at the same level via the transmitting device 9 are received by the receiving device 10 of the monitoring station 1 at the same level, and the image accuracy of each monitor television 2 becomes uniform, making monitoring extremely easy.

Furthermore, the image signals transmitted through each image transmission line 5 are as follows:
The level does not become the same just before the receiving device 10, but the level becomes the same at any position in the transmission direction of each image transmission line 5, so there is no difference in signal level between the image transmission lines 5, and therefore the signal level is the same as in the conventional case. There is no possibility that a high-level image signal leaks into a low-level image signal transmitted through another image transmission line 5.

According to the present invention, the transmitting device 9, the receiving device 10 (including the equalization circuit, etc.), the ITV camera 4,
Since monitor televisions 2 and the like can all be of the same standard, they are compatible and maintenance and operation are facilitated.

Furthermore, since the connection between each ITV camera 4 and the image line transmission line 5 corresponding to the monitor television 2 can be switched freely, images can be transmitted between a desired ITV camera 4 and a desired monitor television 2. All with less monitor TV than 2
The ITV camera 4 can be monitored efficiently, the number of image transmission lines 5 can be reduced, and the system equipment cost can be significantly reduced and the system can be expanded easily.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of a conventional ITV system, FIG. 2 is an explanatory diagram of an ITV system in which a pseudo line is directly inserted into an image transmission line, and FIG. 3 is an explanatory diagram showing an example of an ITV system according to the present invention. . 1... Monitoring station, 2... Monitor TV, 4... ITV camera, 5... Image transmission line, 6... Transmission line switching device, 8... Pseudo line.

Claims (1)

[Claims] 1. A transmission line switching device is installed in the image transmission line connecting the monitor TV of the monitoring station and the ITV camera, and the line switching device is switched by a command from the control unit to transmit images between the desired monitor TV and the desired ITV camera. In the ITV system that enables , an ITV system characterized by being set to the difference in transmission line length from a monitoring station to other ITV cameras.