JPH0746581A - Camera monitoring system - Google Patents

Abstract

PURPOSE:To reduce the number of spread scables to be used by controlling a monitoring camera connected to a terminal station equipment corresponding to a command from a central equipment. CONSTITUTION:A central equipment 11 for controlling a monitor communication network and plural terminal station equipments 12-15 for controlling monitor cameras c1-c4 are connected by a transmission line for sharing a medium composed of first and second loops 1R and 2R. Since the central equipment 11 collects and analyzes specified frames, which are simultaneously sent from the respective terminal station equipments 12-15 detecting faults to the central equipment 11, and specified frames sent from the respective terminal station equipments 12-15 for responding to a response request frame sent from the central equipment 11, the terminal station equipments before and after a fault position are detected. Since the central equipment 11 outputs a transmission line returning instruction to those terminal station equipments and the terminal station equipments receiving this returning instruction execute the transmission line returning operation, the fault position can be detected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a camera monitoring system which can be effectively used, for example, for monitoring power transmission lines, and more particularly to a central unit for controlling a surveillance communication network and a plurality of terminal stations for controlling surveillance cameras. The present invention relates to a camera monitoring system that is configured by connecting a device to a medium sharing type transmission path.

[0002]

2. Description of the Related Art A conventional general camera monitoring system is
Each surveillance camera was directly connected to the control device on a one-to-one basis. As this type of supervisory control method, for example,
The method disclosed in JP-A-3-270531 can be mentioned. In this method, a control request is included in a polling response frame from a terminal device in response to a polling request from the central device, and the central device receiving this control request controls the terminal device that sent the control request. is there. Further, as a method of detecting a failure in a loop type transmission line, for example, the methods disclosed in Japanese Patent Laid-Open Nos. 4-61531 and 4-79641 are known. In the former method, the central device in the loop detects an error by checking the correctness of the transmitted data, sends a specific frame to each terminal device, and responds to it to detect a failure. is there. However, this technology does not consider failure handling. The latter method is a system having two loop transmission lines, a first transmission line and a second transmission line. The present invention proposes a fault detection method in which a monitoring station detects a fault transmission signal and identifies a monitored station by sending it to a second transmission path. However, this technique cannot be applied when a failure occurs in both the first and second transmission paths.

[0003]

All of the general camera monitoring systems shown in the above-mentioned prior art have a structure in which each monitoring camera is directly connected to the control device in a one-to-one correspondence, and therefore the number of cables is the same as the number of monitoring cameras. It only has the problem of being needed. Therefore, a first object of the present invention is to provide a surveillance camera system capable of reducing the number of laying cables used in the camera surveillance system. Further, in the conventional supervisory control method, the terminal device cannot issue a control request unless there is a polling request from the central device, so that there is a problem that it is not possible to promptly deal with an emergency situation such as a failure. It is a thing. Therefore, a second object of the present invention is to send a control request frame from a terminal device that receives an emergency report from an external device to a central device, and the central device that receives the control request frame sends a control request frame. An object of the present invention is to provide a surveillance camera system capable of processing such as controlling a surveillance camera connected to a terminal device.

Regarding the loop type transmission line failure detection method,
The conventional method in which a central device detects a failure due to an error in transmission data has a problem that a terminal device having a failure can be detected, but a failure point cannot be detected when a transmission path fails. It is a thing. Further, in the conventional method in which each terminal device detects a failure, when the terminal device near the failure point reports a failure to the central device, a failure report frame is sent using the second (standby) transmission line. Therefore, in the case of a system having only the first (working) transmission line, there is a problem that failure detection cannot be performed. Furthermore, if a failure occurs simultaneously in the first and second transmission paths, there is a problem that the failure cannot be detected. Therefore, a third object of the present invention is to provide a camera monitoring system capable of detecting a failure and providing an image of a failure point in a camera monitoring system having one loop type transmission path as a medium sharing type transmission path. is there. A fourth object of the present invention is to provide a camera monitoring system having two loop type transmission lines, a first and a second, as a medium sharing type transmission line, in which a failure occurs simultaneously in the first and second transmission lines. It is an object of the present invention to provide a camera monitoring system capable of detecting a failure and providing an image of a failure location even if it occurs, and capable of recovering a transmission path with a simple algorithm.

[0005]

A first object of the present invention is to configure a central device for controlling a surveillance communication network and a plurality of terminal devices for controlling surveillance cameras by a medium sharing type transmission line. The present invention is achieved by a camera monitoring system characterized by controlling a monitoring camera connected to the terminal device according to a command from the central device. Further, the second object of the present invention is to provide a monitoring device for detecting an abnormality of a state in each of the terminal devices, in addition to the means, and to receive a monitoring report from the monitoring device at the terminal device, Further, the terminal device reports the abnormality of the state to the central device, and if necessary, a command from the central device controls a monitoring camera near the monitoring device. Achieved by a camera surveillance system. It should be noted that means for achieving other objects of the present invention will be clarified one after another in the following description.

[0006]

In the camera monitoring system according to the present invention,
First, since the central device for controlling the surveillance communication network and the plurality of terminal devices for controlling the surveillance cameras are connected by the medium sharing type transmission line, the effect of reducing the number of laying cables can be obtained. . Secondly, in response to a monitoring report from an external device for status monitoring, the terminal device sends a control request frame to the central device, and the central device receiving the control request frame sends the control request frame. The effect that it becomes possible to freely control the surveillance camera connected to the transmitted terminal device is obtained. Furthermore, as a third action / effect, each terminal device that has detected a failure sends a specific frame to the central device all at once, and each terminal device responds to a response request frame sent from the central device. The central device collects and analyzes the specific frames to be sent in order to detect the terminal devices before and after the failure point,
The central device issues a transmission path return command to these terminal devices, and the terminal device that has received this return command can detect the failure point by executing the transmission path return operation. Moreover, the transmission path can be restored with a simple algorithm. Furthermore, after the failure processing, by controlling the surveillance cameras before and after the failure location, the effect of visualizing the failure site can be obtained.

[0007]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 shows a configuration diagram of a camera monitoring system having two loop type transmission lines which are opposite to each other as a medium sharing type transmission line to which the present invention is applied. Figure 1
Shows a configuration example of the medium sharing type camera monitoring system according to the first embodiment of the present invention.
And a second loop 2R, a double loop transmission line, a central device 11 for monitoring and controlling the entire system, an end having addresses "1" to "4" for controlling each end station and monitoring the transmission line. The station devices 12 to 15, monitoring cameras C1 to C4 connected to the terminal devices, and external devices 16 to 19 for monitoring the state of the power line and the like. The above-mentioned central device 11 is composed of a central control unit 1B that controls the entire system, and each terminal device 12 to 25 is a terminal control device 1A to 4.
It is composed of A. The central unit 11 continuously generates normal frames 20 described later, and the first loop 1
It is sent to R.

FIG. 2 is a frame format of the normal frame 20 transmitted during the operation of the camera monitoring system according to the present embodiment, and FIG. 3 is a case where a failure occurs during the operation of the camera monitoring system according to the present embodiment. It is a figure which shows the frame format of the failure detection / response frame 30 sent from the terminal devices 12-15. Here, when all the identification units 31 in the format shown in FIG. 3 are “0”, the failure detection frame state is shown, and conversely, when all the identification units 31 are “1”, the response frame state is shown. FIG. 4 shows the frame format of the control request frame 35 transmitted from the terminal device during the operation of the camera monitoring system according to the present embodiment, and FIG. 5 shows the failure during the operation of the camera monitoring system according to the present embodiment. FIG. 6 is a diagram showing a frame format of a control frame sent from the central device to each terminal device in the case of Here, when the type part in the format shown in FIG. 5 is "0", it indicates a response frame request state, and when it is "1", it indicates a loopback operation command state.

FIG. 6 is a block diagram showing a schematic configuration of the central control unit 1B in the central apparatus 11 in the camera monitoring system according to this embodiment. Under normal conditions (when there is no failure), the input of the selector 51 is 1R side, the output of the selector 57 is 1R side, and the output of the selector 58 is 2R.
Regarding the R side and the input of the selector 59, the 2R side is selected. FIG. 7 shows a terminal station control unit 1 in the terminal station devices 12 to 15 in the camera monitoring system according to this embodiment.
It is a block diagram which shows schematic structure of A-4A. Normal time
(When there is no fault), the 1R side is selected for the input of the selector 61, the 1R side is selected for the output of the selector 67, the 2R side is selected for the output of the selector 68, and the 2R side is selected for the input of the selector 69. There is. Hereinafter, the operation of the camera monitoring system according to this embodiment configured as described above will be described with reference to FIGS. In addition,
The camera monitoring system according to claim 4 is as follows in FIG.
This corresponds to the case of having only the first loop 1R.

As an example in the case of no fault, the central unit 11
Camera C connected to the terminal device 12 with address "1"
Consider the case where monitoring is performed according to 1. The central device 11 is
The frame generation block 56 in the central control unit 1B in the central device 11 puts "1" in the DA unit 21 in the normal frame 20 and sends it to the first loop 1R. When the terminal device 12 having the address “1” identifies that the frame received by the frame identification block 62 in the terminal control unit 1A is the normal frame 20, the terminal device 12 sends the received normal frame 20 to the frame processing block 64. . Frame processing block 6
In 4, the image data from the camera C1 is put in the image data section 23 in the normal frame 20 and sent to the first loop 1R. The central device 11 receives the sent normal frame 20 including this image data in the normal frame processing block 54 in the central control unit 1B and monitors it. In addition,
The terminal devices 13 to 15 whose addresses are not “1” relay the above-mentioned normal frame 20 and sequentially send it to the first loop 1R.

When controlling the camera C1 connected to the terminal device 12 having the address '1', the frame control block 56 in the central controller 1B in the central device 11 controls the camera control data in the normal frame 20. The control data is entered in the section 22 and '1' is entered in the DA section 21 for transmission. When the terminal station device 12 having the address “1” identifies that the frame received by the frame identification block 62 in the terminal station controller 1A is the normal frame 20, the received normal frame 2
Send 0 to frame processing block 64. In the frame processing block 64, the above-mentioned camera control data is extracted from the camera control data section 22 in the received normal frame 20, and the camera C1 is controlled according to the extracted camera control data. Then, the image data from the camera C1 is put into the image data section 23 in the normal frame 20 and sent to the first loop 1R. Here, each external device 16-
19 sends monitoring information to the terminal station devices 12 to 15 to which the respective external devices 16 to 19 are connected as necessary, and the monitoring information is processed by the external processing in the terminal station control units 1A to 4A. The terminal devices 12 to 15 received in the block 63 process the data processed on the basis of this monitoring information to the terminal controller 1
The frame processing block 64 in A to 4A inserts it into the external information section 24 in the normal frame 20 and sends it to the first loop 1R.

Upon receiving the normal frame 20 sent from the terminal devices 12 to 15, the central device 11 processes the data based on the data of the external information section 24 in the normal frame 20 or, if necessary, the camera. Move to switching processing. Next, the terminal devices 12 to 15 and the external devices 16 to 1
An example of the operation when an emergency report such as a failure is received from 9 will be described by taking the case where the emergency report is sent from the external device 16 as an example. The terminal device 12 having received the emergency report sent from the external device 16 inserts “1” into the address part 36 in the control request frame 35 in the control request frame generation block 70 in the terminal control part 1A, and The fault data processed from the emergency report is inserted into the information section 37 and transmitted using the transmission line 1R. Upon receiving the control request frame 35 transmitted from the terminal device 12, the central device 11 shifts to processing such as switching to the camera C1 connected to the terminal device 12.

Next, as an example at the time of failure, address "2"
Consider a case where a failure occurs in the first loop 1R between the terminal device 13 of No. 1 and the terminal device 14 of address '3'.
The terminal device 14 of the address “3” detects that the normal frame 20 does not arrive from the terminal device 13 of the address “2” by disconnecting the signal, and detects a failure in the terminal control unit 3A in the terminal device 14. In the response frame generation block 65, all the identification parts 31 in the failure detection / response frame 30 are set to “0”,
The fault detection / response frame 30 having its own address '3' in the address section 32 is generated and sent to the first loop 1R. Also, the same operation is performed in the terminal device 15 on the downstream side of the transmission path (hereinafter, this is also referred to as “downstream” and “upstream” is the same) than the terminal device 14 with the address “3”. In addition,
The terminal device 15 relays the fault detection / response frame 30 sent from the upstream terminal device 14 to the downstream. Fault detection / response frame 3 sent from the terminal devices 14 and 15
The central device 11 which has received 0 receives the frame identification block 5
The frame received in 2 is identified as the failure detection / response frame 30, and the failure detection / response frame 30 is sent to the address detection block 53.

In the address detection block 53, the lowest address "3" is detected from the address parts 32 of the failure detection / response frame 30 collected from each terminal device, and the nearest to the downstream of the failure location is the closest. The terminal device 14 is specified. According to the camera monitoring system shown in this embodiment,
Since the central device for controlling the surveillance communication network and the plurality of terminal devices for controlling the surveillance cameras are connected by the medium sharing type transmission line, it is possible to reduce the number of laying cables. Further, in response to a monitoring report from an external device for status monitoring, the terminal device sends a control request frame to the central device, and the central device receiving the control request frame,
The effect that it becomes possible to freely control the surveillance camera connected to the terminal device that has sent the control request frame is obtained.

Next, a second embodiment of the present invention will be described below.
This will be described with reference to FIGS. Regarding the operation when there is no failure in the camera monitoring system according to the present embodiment,
Since it is the same as the previous embodiment, a description thereof will be omitted, and an example of a failure will be described. Also, here, as an example at the time of failure, the terminal station device 13 of the address "2" and the terminal station device 1 of the address "3"
Consider the case when a failure occurs in both the first loop 1R and the second loop 2R between 4 and 4. The terminal device 14 of the address “3” detects that the normal frame 20 does not arrive from the terminal device 13 of the address “2” by disconnecting the signal,
In the fault detection / response frame generation block 65 in the terminal control unit 3A in the terminal device 14, all the identification units 31 in the fault detection / response frame 30 are set to "0", and the own address "3" is set in the address unit 32. The entered fault detection / response frame 30 is generated and sent to the first loop 1R. Address '3'
The same operation is performed in the terminal device 15 downstream of the terminal device 14.

The terminal device 15 relays the fault detection / response frame 30 sent from the upstream terminal device 14 to the downstream. In addition, the terminal devices 14 and 15 generate the failure detection / response frame 30 or relay the failure detection / response frame 30 sent from the upstream terminal device,
By the timer monitoring function of the frame identification block 62 in the terminal control units 3A and 4A, if the failure detection / response frame 30 sent from the upstream is not received within a certain fixed time,
In response to a command from the loop switching block 66 in the terminal control units 3A and 4A, the input of the selector 61 is the selector 68 side, the output of the selector 67 is the selector 69 side, and the output of the selector 68 is the selector 61 side, the input of the selector 69. To the selector 67 side. The central unit 1 which has received the fault detection / response frame 30 sent from each terminal unit 14, 15.
1 identifies that the frame received by the frame identification block 52 in the central control unit 1B is the fault detection / response frame 30, and sends the fault detection / response frame 30 to the address detection block 53.

In the address detection block 53, the terminal device 1
The lowest address “3” is detected from the address parts 32 of the failure detection / response frame 30 collected from Nos. 4 and 15, and the closest terminal station device 14 downstream from the failure location is specified. Next, the central unit 11 sets the type section 41 in the control frame 40 to "0" in the frame generation block 56 in the central control section 1B and sets the DA1 section 42 to the address "1".
The control frame 40 to which "1" is sequentially added is transmitted to the terminal devices 12 and 13 using the first loop 1R, and at the same time, the input of the selector 51 is input to the selector 58 side in accordance with the instruction from the failure processing block 55. , The output of the selector 57 is switched to the selector 59 side, the output of the selector 58 is switched to the selector 51 side, and the input of the selector 59 is switched to the selector 57 side.

The terminal devices 12 and 13 which have received the control frame 40 sent from the central device 11 are the frame identification blocks 62 in the terminal control units 1A and 2A, which are the control frames 40, And control frame 4
It is confirmed that the type part 41 in 0 is "0", all the identification parts 31 in the failure detection / response frame 30 are set to "1" in the failure detection / response frame generation block 65, and the own address is set in the address part 32. Insert the loop switch block 66
Command from the selector 68 side,
The output of the selector 68 is switched to the selector 62 side, the output of the selector 67 is switched to the selector 69 side, and the input of the selector 69 is switched to the selector 67 side, and the failure detection / response frame 30 is directed to the central device 11 to the second loop 2R. Send out. After transmitting the failure detection / response frame 30 described above, the terminal station apparatus 12 that receives the failure detection / response frame 30 transmitted from the upstream terminal station apparatus 13 relays to the downstream side.

The terminal devices 14, 15 are the terminal devices 1
The timer detection function of the frame identification block 62 in the internal terminal station control units 3A and 4A generates a failure detection / response frame 30 or a failure detection / response frame 30 transmitted from an upstream terminal station device. If the failure detection / response frame 30 sent from the upstream is not received within a certain time after the reception, the frame identification block 62 in the terminal station devices 14 and 15 inside the terminal station control units 3A and 4A The command switches the input of the selector 61 to the 1R side, the output of the selector 68 to the 2R side, the output of the selector 67 to the 1R side, and the input of the selector 69 to the 2R side. Terminal device 1
When the central device 11 that has received the failure detection / response frame 30 sent from the communication devices 4 and 15 identifies that the frame received by the frame identification block 52 in the central control unit 1B is the failure detection / response frame 30, Failure detection
The response frame 30 is sent to the address detection block 53 in the central controller 1B.

Next, in the address detection block 53, the highest order address '2' is detected from the addresses in the failure detection / response frame 30 collected from the terminal equipments 12 and 13, and the failure processing block 55 outputs According to the instruction, the input of the selector 51 is 1R side and the output of the selector 57 is 1R side
Side, and the output of the selector 58 is the 2R side, the selector 5
The input of 9 is switched to the 2R side. In the frame generation block 56 in the central control unit 1B, the type part 41 and the DA1 part 42 in the control frame 40 are set to "1" and "address", respectively.
2 ', DA2 section 44 is address'3', flag 1 section 43
The flag 2 section 45 is set to “0” (folding operation instruction) and the first loop 1R is used to control the control frame 40.
Is sent to the terminal device 13 of the address '2'. In the terminal station device 13 having the address "2" which receives the control frame 40 sent from the central device 11, the type identification section 62 in the control frame 40 is set to "1" in the frame identification block 62 in the terminal station control section 1A. Identify that.

Next, in the frame processing block 64, the flag 1 portion 43 in the control frame 40 is set to "1". Then, the frame identification block 62 issues a loopback operation command to the loop switching block 66, and the loop switching block 66 receiving this command outputs the output of the selector 67 to the selector 69 side and the input of the selector 69 to the selector 67 side, respectively. Switch (Execute looping operation). Next, the second loop 2R is used to address the control frame 40.
It is sent to the 3'terminal device 14. While transmitting this control frame 40, the terminal station devices 15 other than the terminal device 14 of the address '3' which selects the second loop 2R,
The control frame 40 transmitted from the terminal device 13 having the address “2” is transferred to the frame identification block 6 in the terminal controller 4A.
2, it is confirmed that the received frame is the control frame 40, the type part 41 in the control frame 40 is “1”, and the flag 1 part 43 is “1”, and the received control frame 40 is At the same time as relaying to the second loop 2R, the input of the selector 61 is set to the 1R side and the selector 67 by an instruction from the loop switching block 66 in the terminal station control unit 4A.
The output of 1R side, the output of the selector 68 is 2R side,
The input of the selector 69 is switched to the 2R side.

The terminal device 14 of the address 3 which has received the control frame 40 transmitted from the terminal device 13 of the address 2
Is a frame identification block 62 in the terminal control unit 3A,
It is confirmed that the type part 41 in the control frame 40 is "1". Next, the frame identification block 62 issues a loopback operation command to the loop switching block 66, and the loop switching block 66 that receives this command switches the input of the selector 61 to the selector 68 side and the output of the selector 67 to the 1R side ( (Foldback operation execution), the frame processing block 64 sets the flag 2 portion 45 in the control frame 40 to '
As 1 ', the control frame 40 is sent to the central unit 11 using the first loop 1R. Upon receiving this control frame 40, the central unit 11 receives the flag 1 in the control frame 40 in the failure processing block 55 in the central control unit 1B.
After confirming that the units 43 and 2 are '1', normal operation is resumed. In addition to the above-described embodiment, the central device 11 may select and monitor a plurality of monitoring cameras C1 to C4 at the same time.

According to the camera monitoring system shown in the above-mentioned embodiment, the specific frames which the terminal devices that have detected the failure send to the central device all at once, and the terminal devices are sent from the central device. The central device collects and analyzes the specific frames sent to reply to the response request frame and detects the terminal devices before and after the failure point, and the central device transmits the transmission path to these terminal devices. By issuing a loopback command and receiving the loopback command, the terminal device can detect the faulty point by executing the loopback operation of the transmission path. Furthermore, after the fault processing, the monitoring cameras before and after the faulty point can be detected. By controlling, it is possible to obtain the effect that visualization of the failure site becomes possible. It is needless to say that the above embodiment shows one example of the present invention, and the present invention should not be limited to this.

[0024]

As described above in detail, according to the present invention, a camera monitoring system having a medium sharing type transmission line, in particular, a loop type transmission line enables the reduction of laying cables, and The remarkable effect is that it is possible to realize a camera monitoring system capable of switching cameras according to the information of the external monitoring device. Further, in the case of a camera monitoring system having two loop type transmission lines in opposite directions, a camera monitoring system capable of detecting a failure point and enabling failure processing with a simple algorithm is provided. The effect is that it can be realized. Further, after the failure processing, there is an effect that it is possible to realize a camera monitoring system that enables visualization of a failure site by cameras before and after the failure location.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a camera monitoring system according to an embodiment of the present invention, which has two loop type transmission lines which are opposite to each other as medium sharing type transmission lines.

FIG. 2 is a diagram showing a frame format of a normal frame transmitted during operation of a camera monitoring system having a loop type transmission path according to an embodiment.

FIG. 3 is a diagram showing a frame format of a failure detection / response frame sent from each terminal device when a failure occurs during operation of the camera monitoring system having the loop type transmission line according to the embodiment.

FIG. 4 is a diagram showing a frame format of a control request frame transmitted from each terminal device during operation of a camera monitoring system having a loop type transmission path according to an embodiment.

FIG. 5 is a diagram showing a frame format of a control frame sent from the central device to each terminal device when a failure occurs during operation of the camera monitoring system having the loop type transmission line according to the embodiment.

FIG. 6 is a block diagram of a central control unit in a central device in a camera monitoring system having a loop type transmission line according to an embodiment.

FIG. 7 is a block diagram of a terminal station controller in the terminal device in the camera monitoring system having a loop type transmission line according to the embodiment.

[Explanation of symbols]

11: Central device, 1B: Central control unit, 12 to 15: Terminal device, 16 to 19: External device, C1 to C4: Monitoring camera, 1A to 4A: Terminal control unit, 1R: First loop, 2
R: second loop, 20: normal frame, 21: DA
Part, 22: camera control data part, 23: image data part,
24: external information part, 31: identification part, 32: address part,
35: control request frame, 36: address part, 37: external information part, 41: type part, 42, 44: DA1 part, D
A2 part, 43: flag 1 part, 45: flag 2 part, 51,
57, 58, 59: selector, 52: frame identification block, 53: address detection block, 54: normal frame processing block, 55: failure processing block, 56: frame generation block, 61, 67, 68, 69: selector, 62 : Frame identification block, 63: external processing block, 64: frame processing block, 65: failure detection
Response frame generation block, 66: loop switching block, 70: control frame generation block.

Claims (6)

[Claims] 1. A camera surveillance system comprising a central device for controlling a surveillance communication network and a plurality of terminal devices for controlling surveillance cameras, which are connected by a medium-sharing transmission line. A camera monitoring system which controls a monitoring camera connected to the terminal device according to a command. 2. In addition to the respective means, a monitoring device for detecting a state abnormality in each of the terminal devices is provided, a monitoring report from the monitoring device is received by the terminal device, and further, from the terminal device. The camera monitoring system according to claim 1, wherein a monitoring camera near the monitoring device is controlled by a command from the central device, if necessary, by reporting an abnormality in the state to the central device. system. 3. In addition to the respective means, a monitoring device for detecting a state abnormality in each of the terminal devices is provided, the terminal device receives a monitoring report from the monitoring device, and further, if necessary, The camera monitoring system according to claim 1, wherein the central device controls a monitoring camera near the monitoring device that has issued the emergency report by issuing an emergency report from the monitoring device. 4. In addition to the respective means, a loop type transmission line is provided as the medium sharing type transmission line, and a specific frame is generated when any of the plurality of terminal station devices detects a transmission line failure. The central device collects and analyzes the specific frames sent from each of the terminal devices, detects the closest terminal device downstream from the failure point, and outputs from the terminal device to the transmission device. The camera monitoring system according to any one of claims 1 to 3, wherein the monitoring camera is directed to the obstacle location. 5. In addition to each of the above means, two loop-shaped transmission lines that are opposite to each other are provided as the medium sharing type transmission line, and any one of the plurality of terminal station devices detects a transmission line failure. In this case, a specific frame is generated and transmitted to the transmission line, the central device collects and analyzes the specific frames transmitted from the terminal devices, detects the terminal devices before and after the failure point, The camera monitoring system according to any one of claims 1 to 3, wherein a monitoring camera is directed from the terminal device to the fault location. 6. The central device outputs a loopback command of a transmission path to the terminal device before and after the failure point after detecting the terminal devices before and after the failure point, and the terminal device receiving this command outputs the command. The camera monitoring system according to claim 5, wherein the operation of folding back the transmission path is executed.