GB2573924A

GB2573924A - Car network system and car reversal position detecting method

Info

Publication number: GB2573924A
Application number: GB1911435.4A
Authority: GB
Inventors: Matsukawa Tomoki
Original assignee: Hitachi Kokusai Electric Inc
Current assignee: Hitachi Kokusai Electric Inc
Priority date: 2017-02-27
Filing date: 2017-02-27
Publication date: 2019-11-20
Also published as: WO2018154742A1; GB201911435D0; JPWO2018154742A1; JP6753998B2

Abstract

The present invention enables a car reversal position in a car network system configured by coupling a plurality of cars to be automatically detected. This car network system is provided with a central processing unit (14) that communicates with switching hubs (11, 21, 31, 41) of cars (V1-V4) to detect a car reversal position. The relationship between ports used for connection between the respective switching hubs of adjacent cars differs between when the adjacent cars have the same orientation and when the adjacent cars have the opposite orientations. The central processing unit acquires, from the switching hub of each of the cars, the MAC address of this switching hub, the MAC address of another switching hub connected to this switching hub, and the port numbers of ports used for this connection, and detects a car reversal position on the basis of the relationship between the ports used for connection between the switching hubs of the adjacent cars, the relationship being specified from the acquired respective MAC addresses and port numbers.

Description

DESCRIPTION

Title of the Invention: TRAIN CAR NETWORK SYSTEM AND METHOD FOR DETECTING POINT AT WHICH DIRECTION OF CARS IS REVERSED

TECHNICAL FIELD [0001] The present invention relates to the detection of a point at which the direction of cars is reversed in a train car network system that is formed by connecting the cars that form a train through an IP network.

BACKGROUND ART [0002] In a train monitoring system, a driver or a trainman confirms passengers who are moving on a platform with images so as to check the safety of the passengers before controlling the opening and closing of the doors. The images of the passengers are taken by cameras that are installed on the main bodies of the cars or on the platform. In the system that is common in Japan, for example, cameras that are installed on the platform are used to display images on the monitor in the platform or on the monitor in the cabin of the train. Meanwhile, in the system that is common in England, for example, cameras that are installed on the side of the main bodies of the cars are used to display images on the monitor in the cabin. This difference is caused by the difference of whether the operation of the train and the infrastructure are managed by the same business entity or different business entities.

The following description refers to an on-board camera type train monitoring system where cameras are installed on the main bodies of the cars. Patent Document 1, for example, discloses a train monitoring system where cameras are arranged on the respective doors of the cars so as to be adjacent to each other.

CITATION LIST

PATENT DOCUMENT [0003] Patent Document 1: International Unexamined Patent Publication 2015/145736

SUMMARY OF THE INVENTION

TECHNICAL PROBLEM [0004] In a conventional train monitoring system, it is required for the safety of the passengers to be monitored in real time, and therefore, an analog system where no delay takes place is prioritized for use. In recent years, however, a low delay

transmission	has become possible	due	to	the	progress	of	IP
technology,	and therefore, all the	devices	are	connected	to	an
IP network.	As for one advantage	of	IP	systems,	an	IP

technology allows one cable to make connections between the devices, and therefore, the costs of the cables can be reduced. Furthermore, one cable allows for the transmission of not only image data, but also other information including alarm information or train information. The images taken by a number of cameras are encoded by the respective cameras, transmitted to a monitor via the IP network, and decoded in the monitor so as to be displayed on the divided areas of the screen.

[0005] In the case where cameras are installed on the sides of each car, the positions at which the cameras are installed vary depending on the structure of the car. This is because mass produced cars have the same structure even in the case where the

positions at which	cameras are installed	differ	between	the
right side and	the	left side.	When	these cars	are	connected	to
form a train,	the	direction of the cars	is	reversed with a
certain point as the	; border.
Typically,	as	illustrated	in	FIG. 1,	a	first car VI,	a
second car V2,	, a	fourth car	V4	and a	third	car V3	are
manufactured so	as	to have the	same structure	when	oriented	in

the same direction. When they are linked, the direction of the cars is reversed with the linking portion between the car V2 and the car V3 as the border. That is to say, the cars VI and V2 that are oriented forward are linked to the cars V3 and V3 that are oriented backwards. As a result, in the two front cars VI and V2 and the two rear cars V3 and V4, a positional relationship between the cameras that are installed on one side (side A) of the respective cars and the cameras that are installed on the other side (side B) is reversed.

[0006] This reversal becomes a problem, for example, in a case where the images of all the cameras that are provided on the side where the doors of the respective cars are opened are displayed in order to monitor the passengers who are getting on or off while the train is stopped. FIG. 2 shows an example where the images taken by the cameras of the respective cars are collectively displayed on a monitor of which the screen area is divided into four in the case where the doors on the right side open with the car VI side being the direction in which the train travels in FIG. 1. As shown in FIG. 2, when images of the cameras (side A) in the two front cars VI and V2 are displayed, images of the cameras (side B) in the two rear cars V3 and V4 behind the point of reversal need to be displayed on the same screen .

Therefore, the central unit of the train monitoring system needs to grasp the structure of the cars and recognize at which point the direction of the cars is reversed before the operation [0007] Some railway systems receive information on the car structure from the upper system that manages the car structure so that it can recognized at which point the direction of the cars is reversed. An example of the upper system is TMS (Train Management System) . However, only a few trains have TMS, and a mechanism for detecting that the direction of the cars is reversed without such a system is required.

[0008] The present invention is provided in view of the abovedescribed conventional situation, and an object thereof is to make it possible for the point at which the cars are reversed to be detected automatically in a train car network system that is formed by linking a plurality of cars.

SOLUTION TO PROBLEM [0009] In order to achieve the above-described object, the train car network system and the method for detecting a point at which the cars are reversed according to the present invention are formed as follows.

(1) A train car network system formed by connecting network relays that are installed for a plurality of cars is characterized in that the train car network system is provided with a detection device for detecting a point at which cars are reversed through communication with the network relay in each car, the network relay in each car has a plurality of ports for connection with other devices, and the detection device acquires from the network relay in each car, an address value for identifying the network relay, an address value of another network relay that is connected to the network relay, and a port number for identifying the port that is used for the connection, and detects the point at which cars are reversed on the basis of the relationship of the ports used for the connection between the network relays in adjacent cars, which is specified by the address values and the port numbers that have been acquired.

[0010] (2) The train car network system according to the above (1) is further provided with: cameras provided on the respective sides of each car; a monitor for displaying images that are taken by cameras in each car; and a display control unit for controlling a display on the monitor, and is characterized in that the display control unit selects a camera for acquiring the image on the basis of the point at which cars are reversed that has been detected by the detection device and allows the image taken by the selected camera to be displayed on the monitor.

[OOli] (3) A method for detecting a point at which cars are reversed, in a train car network system that is formed by connecting network relays installed for a plurality of cars is characterized in that the network relay in each car has a plurality of ports for a connection with another device, a detection device that is connected to communicate with the network relay in each car acquires, from the network relay in each car, an address value for identifying the network relay, an address value for another network relay that is connected to the network relay, and a port number for identifying the port that is used for the connection, and detects the point at which cars are reversed on the basis of the relationship of the ports used for the connection between network relays in adjacent cars, which is specified by the address values and the port numbers that have been acquired.

ADVANTAGEOUS EFFECTS OF THE INVENTION [0012] According to the present invention, a point at which cars are reversed in a train car network system that is formed by linking a number of cars can be automatically detected.

BRIEF DESCRIPTION OF DRAWINGS [0013] FIG. 1 is a schematic diagram showing an example of the configuration of a train;

FIG. 2 is a diagram showing an example of a display of images taken by cameras on divided areas of a screen;

FIG. 3 is a diagram showing an example of the configuration of the train car network system according to one embodiment of the present invention;

FIG. 4 is a diagram showing an example of the connection between the switching hubs in the train car network system in FIG. 3;

FIG. 5 is a diagram showing an example of a MAC address table in the train car network system in FIG. 3;

FIG. 6 is a diagram showing an example of the process sequence concerning the collection of MAC addresses in the train car network system in FIG. 3;

FIG. 7 is a flow chart showing an example of the process sequence concerning the checking of the point at which cars are reversed in the train car network system in FIG. 3;

FIG. 8 is a flow chart showing an example of the process sequence concerning the control of start/end the display of images taken by cameras in the train car network system in FIG. 3; and

FIG. 9 is a flow chart showing an example of the process sequence concerning the specification of the image taken by the camera to be displayed in the train car network system in FIG. 3 DESCRIPTION OF EMBODIMENTS [0014] One embodiment of the present invention is described in reference to the drawings.

FIG. 3 shows an example of the configuration of a train car network system provided with a function of detecting a location at which cars are reversed. Though the description of the present embodiment refers to an example of a train car network system in cars that travel along a railroad, the same can be applied to other train car network systems such as a train car network system for cars that travel along a monorail. In the train car network system according to the present embodiment, a switching hub (SW) and cameras are installed in each car, and they are connected through an IP network. In addition, one central processing unit (CPU) is provided within a train. The central processing unit is a device for generally controlling the train car network system, and has a function of detecting a location at which cars are reversed.

[0015] A switching hub 11 and a camera (side A) 12, a camera (side B) 13, a central unit 14 and a monitor 15 that are connected to the switching hub 11 are installed in the first car VI. A switching hub 21 and a camera (side A) 22 and a camera (side B) 23 that are connected to the switching hub 21 are installed in the second car V2. A switching hub 31 and a camera (side A) 32 and a camera (side B) 33 that are connected to the switching hub 31 are installed in the third car V3. A switching hub 41 and a camera (side A) 42 and a camera (side B) 43 that are connected to the switching hub 41 are installed in the fourth car V4.

[0016] The switching hubs in the adjacent cars (11 and 21, 21 and 31, 31 and 41) are respectively connected through a network cable. That is to say, the switching hubs in the respective cars are connected in a row so as to build a communication network within the train.

The cameras 12, 13, ... 42 and 43 are installed on the outer sides of the cars so that images in the vicinity of the doors of the cars can be taken, for example. In the present embodiment, DOO (driver only operation) cameras, which are a type of IP

camera,	are	used, although other	types	of cameras may be	used.
In	the	present	embodiment,	the monitor is	provided	only in
the car	VI	that has	a cabin (or	the	trainman'	s room),	although

it may be provided in another car (car V4, for example) where a cabin is provided. In the present embodiment, the central unit is provided only in the car VI, although central units may be provided in other cars so as to work in coordination.

[0017] FIG. 4 shows an example of the connection of switching hubs .

The cars are manufactured so as to have the same structure, and therefore, the ports of the switching hubs for the connection between the cars are fixed. In the present embodiment, a port Pl which is the first port and a port P2 which is the second port in each switching hub are used for the connection between the cars. The port Pl is used for the connection with the car on the front side, and the port P2 is used for the connection with the car on the rear side. Here, the front side means the leading side (the car VI or V4 side) in the state before the cars VI and V2 and the cars V3 and V4 are linked (see the left half of FIG. 1), and the rear side means the opposite side thereof. That is to say, the port P2 of the switching hub 11 in the car VI on the front side and the port Pl of the switching hub 21 in the car V2 on the rear side are connected for the connection between the car VI and the car V2. Likewise, the port P2 of the switching hub 41 in the car V4 on the front side and the port Pl of the switching hub 31 in the car V3 on the rear side are connected for the connection between the car V3 and the car V4.

[0018] When the switching hubs in the respective cars are connected in accordance with such a rule, ports having the same number are used for the connection between the switching hubs in the cars through the position at which the direction of the cars is reversed. In FIG. 4, the switching hub 21 in the car V2 and the switching hub 31 in the car V3 are connected by using the port P2 on either side.

[0019] As illustrated in FIG. 5, different MAC addresses (Media Access Control addresses) are allocated to the switching hubs in the respective cars. The respective switching hubs have a MAC address table for managing the MAC addresses of the facing devices (other devices that are connected to the switching hub) for each port.

[0020] In the example in FIG. 5, the MAC address of the switching hub in the car V2 is recorded in the port P2 in the MAC address table of the switching hub in the car VI, and at the same time, the MAC address of the switching hub in the car VI is recorded in the port Pl in the MAC address table of the switching hub in the car V2 . In addition, the MAC address of the switching hub in the car V3 is recorded in the port P2 in the MAC address table of the switching hub in the car V4, and at the same time, the MAC address of the switching hub in the car V4 is recorded in the port Pl in the MAC address table of the switching hub in the car V3. That is to say, in the case where the cars are connected to each other without the direction of the cars being reversed, the MAC address of the partner is mutually recorded in different port field of the MAC address table in each switching hub.

[002i] In contrast, the MAC address of the switching hub in the car V3 is recorded in the port P2 in the MAC address table of the switching hub in the car V2, and at the same time, the MAC address of the switching hub in the car V2 is recorded in the port P2 in the MAC address table of the switching hub in the car V3. That is to say, in the case where the cars are connected to each other with the direction of the cars being reversed, the MAC address of the partner is mutually recorded in the same port field of the MAC address table in each switching hub .

[0022] FIG. 6 shows an example of a process sequence concerning the collection of MAC addresses.

The central unit 14 first transmits a MAC address request to the switching hub in the car VI (step Sil), and receives the MAC address that is transmitted from the switching hub in the car VI in response to this request (step S12). Next, the central unit 14 transmits a MAC address table request to the switching hub in the car VI (step S13), and receives the MAC address table that is transmitted from the switching hub in the car VI in response to this request (step S14) . The MAC address and the MAC address table can be acquired by using SNMP (Simple Network Management Protocol) or LLDP (Link Layer Discovery Protocol) .

Likewise, the central unit 14 sequentially accesses the switching hubs of the cars V2, V3 and V4 so as to acquire the MAC address and the MAC address table from each switching hub (steps S21 through S44).

The central unit 14 checks the point at which the cars are reversed after having finished acquiring the MAC address and the MAC address table from all the switching hubs (step S60).

[0023] FIG. 7 shows an example of the process sequence concerning the checking of the point at which the cars are reversed.

In the checking of the point at which the cars are reversed, first it is determined whether the switching hubs in adjacent cars are connected to each other using the mutual ports Pl. That is to say, it is determined that whether the car V2 is connected to the port Pl of the switching hub in the car VI and the car VI is connected to the port Pl of the switching hub in the car V2 (step S61) . In the case where the determination result is Yes, the point between the car VI and the car V2 is detected at the point at which the cars are reversed (step S62). Likewise, the determination is made between the car V2 and the car V3 as well as between the car V3 and the car V4 (steps S63 through S66) .

[0024] Next, it is determined whether the switching hubs in adjacent cars are connected to each other using the mutual ports P2 . That is to say, it is determined whether the car V2 is connected to the port P2 of the switching hub of the car VI and the car VI is connected to the port P2 of the switching hub in the car V2 (step S67) . In the case where the determination result is Yes, the point between the car VI and V2 is detected as the point at which the cars are reversed (step S68). Likewise, the determination is made between the car V2 and the car V3 as well as between the car V3 and the car V4 (steps S69 through S72) .

[0025] That is to say, in the checking of the point at which the cars are reversed, the combination of switching hubs in adjacent cars where the mutual MAC addresses are recorded in the ports of the same number is searched for. Thus, in the case where the corresponding combination is found, it is determined that the direction of the cars is reversed at the point between the cars.

As described above, in the train car network system according to the present embodiment, the point at which the cars are reversed can be detected by simply checking the connection configuration between the switching hubs in the respective cars.

There may be a plurality of cases in the checking of the point at which the cars are reversed where the determination result is Yes. This is because there may be a plurality of points at which the cars are reversed when many cars are linked. Therefore, a plurality of points at which the cars are reversed can be managed by preparing a plurality of variables having the data on the points at which the cars are reversed. In this case the same logic as in the above description can be used for the determination .

[0026] Next, the control of the display of the images taken by the cameras in the train car network system according to the present embodiment is described. FIG. 8 shows an example of the process sequence concerning the control of the start/end of the display of images taken by the cameras.

Here, the start or the end of the delivery of the images taken by the cameras 12, 13, ... 42 and 43 in the respective cars can be controlled via a network. In addition, at the start of the operation of the train, the monitor 15 has acquired from the central unit 14 and stored the data on the frames for cutting out the images taken by the respective cameras and the data on the control of the divided display, and the divided display is controlled on the basis of these data. The data on the control of the divided display includes the data on the format for dividing the display region on the monitor and the data on the display numbers for identifying the respective divided areas . In addition, the central unit 14 has known in advance the positional relationship between the cameras 12 and 13 and the sides of the bodies of the cars that had been determined at the time of manufacture. For example, the determination may be made depending on the IP address in such a manner that the cameras of which the fourth octet of the IP address is 1 (10.0.0.1, for example) are on the left side, and the cameras of which the fourth octet of the IP address is 2 (10.0.0.2, for example) are on the right side.

[0027] The central unit 14 determines whether or not the train has stopped at a station on the basis of the speed of the train (step S101) . Whether or not the train has stopped at a station can be determined, for example, by determining whether the speed of the train is a predetermined speed or higher or less than the predetermined speed. As for the predetermined speed, 3 km/h can be used, for example, but it is not limited to this, and any speed with which it is possible to determine whether or not the train is stopped may be used.

The central unit 14 determines whether or not the doors of the cars are open in the case where it has been determined that the train is stopped at a station in step S101 (step S102).

[0028] The central unit 14 transmits an instruction to start the display of images on the monitor 15 in the case it has been determined that the doors of the cars are open in step S102 (step S103) . At this time, the central unit 14 transmits to the monitor 15 simultaneously or sequentially the train traveling direction data that indicates whether the direction in which the train travels is towards the car VI side or towards the car V4 side, the entrance data that indicates whether the side where the doors open is the right side or the left side for the passengers to get on and get off, and the car reversal point data that indicates the point at which the cars are reversed.

The monitor 15 shows the divided display of the images that have been taken by a plurality of cameras in response to the reception of the instruction to start the display of images from the central unit 14 (step S104). After that, the procedure returns to step S101 in order to repeat the process.

[0029] In the case where the central unit 14 has determined that the train is not stopped at the station in step S10I or in the case where it has been determined that the doors of the cars are not open in step S102, an instruction to stop the display of images is transmitted to the monitor 15 (step S105) . In the case where the display of images has not been started, nothing needs to be done. Hereinafter, the procedure returns to step S101 in order to repeat the process.

[0030] Here, in the train network system according to the present embodiment, the divided display is shown in such a mode where the driver or the trainman can easily recognize the areas being monitored that correspond to the respective images taken by the cameras taking into consideration the arrangement on the monitor of the respective images taken by the cameras. As an example, the images taken by the cameras are arranged on the monitor 15 following the logic that the images taken by the cameras of which the order follows the direction in which the train is traveling are allocated to the divided areas in the order starting from the upper left to the lower right on the monitor .

[0031] In the following, the specification of the images taken by the cameras that are to be shown on the divided display in step S104 is described. FIG. 9 shows an example of the process sequence concerning the specification of images taken by the cameras. Here, a case where the display region on the monitor 15 is divided into four sections where the images taken by the cameras in the train consisting of four cars are displayed is described as an example. The minimum car number is 1, the maximum car number is 4, and the point at which the cars are reversed is 3.

[0032] The monitor 15 acquires the train traveling direction data, the entrance data, and the car reversal point data that are transmitted from the central unit 14 at the time of instruction to start the display of the images (step S121) .

Next, the monitor 15 determines on the basis of the train traveling direction data whether the direction in which the train is traveling is towards the car VI side (the direction towards the first car) or towards the car V4 side (the direction towards the fourth car) (step S122) .

[0033] In the case where the direction in which the train is traveling is towards the car VI side, the minimum car number is set as the variable X, and at the same time, the point at which the cars are reversed is set as the variable Y (step S123) . In the present embodiment, 1 is set to the variable X, and 3 is set to the variable Y.

Next, it is determined on the basis of the entrance data whether the side where the doors open is on the right or on the left (step S124) . In the case where the doors on the right side open, the system is set such that the images taken by the cameras on side A are used for the cars when X < Y, and the images taken by the cameras on side B are used for the cars when X = Y (step S125). In the case where the doors on the left side open, the system is set such that the images taken by the cameras on side B are used for the cars when X < Y, and the images taken by the cameras on side A are used for the cars when X 1 Y (step S126)

Next, 1 is added to the value of the variable X (step sl27), and it is determined whether or not X > the maximum car number (step S128) . In the case where X > the maximum car number is not present, the procedure returns to step S124, whereas in the case of X > the maximum car number, the process is complete.

[0034] In the case where the direction in which the train is traveling is not towards the car VI side (in the case where the direction is towards the car V4 side), the maximum car number is set to the variable X, and at the same time, the point at which the cars are reversed is set to the variable Y (step S129) . In the present embodiment, 4 is set to the variable X, and 3 is set to the variable Y.

Next, it is determined on the basis of the entrance data whether the side where the doors open is on the right or on the left (step S130) . In the case where the doors on the right side open, the system is set so that the images taken by the cameras on side B are used for the cars when X < Y, and the images taken by the cameras on side A are used for the cars when X Y (step S131) . In the case where the doors on the left side open, the system is set so that the images taken by the cameras on side A are used for the cars when X < Y, and the images taken by the cameras on side B are used for the cars when X Y (step S132).

Next, 1 is subtracted from the value of the variable X (step S133), and it is determined whether or not X < minimum car number (step S134) . In the case where X < minimum car number is not present, the procedure returns to step S130, whereas in the case of X < minimum car number, the process is complete.

[0035] As a result, the images taken by the cameras that are subject to the divided display can be specified. Here, the above-described process flow is merely an example, and there are various other techniques that can be used to specify the images taken by the cameras that are subject to the divided display.

Though the monitor 15 specifies the images taken by the cameras in the above description, the central unit 14 may specify the images taken by the cameras, for example. Though the images taken by the cameras are specified when the images are displayed in the above description, the images taken by the cameras that are used in the case where the doors on the right side open and the images taken by the cameras that are used in the case where the doors on the left side open may be specified in advance .

[0036] Though a train having one point at which the cars are reversed is cited as an example in the above description, there may be a plurality of points at which the cars are reversed. In such a case, the respective points at which the cars are reversed are specified in accordance with the process sequence in FIG. 7, for example, and thus, the images taken by the cameras on the side where the doors open may be specified while switching the images taken by the cameras on side A and the images taken by the cameras on side B with the respective points at which the cars are reversed being a border.

[0037] As described above, the train car network system according to the present embodiment is configured by connecting the switching hubs (11, 21, 31 and 41) that are installed for a plurality of cars (VI through V4). The train car network system is provided with a central unit (14) that communicates with the switching hub in each car in order to detect a point at which the cars are reversed. The relationship between the ports that are used for the connection between the switching hubs in adjacent cars is different between the case where the adjacent cars are in the same direction and the case where the adjacent cars are in the opposite direction. Thus, the central unit acquires from the switching hub in each car the MAC address for identifying the switching hub, the MAC address of the other switching hub that is connected to the switching hub, and the port number for identifying the port that are used for the connection, and detects a point at which the cars are reversed on the basis of the relationship of the ports that are used for the connection between the switching hubs in the adjacent cars, which is specified from the thus-acquired MAC addresses and port numbers .

[0038] That is to say, the mechanism for detecting a point at which the cars are reversed is provided by checking which ports are used for the connection between the switching hubs in the respective cars on the basis of the supposition that the relationship between the ports that are used for the connection between the switching hubs in adjacent cars is different between the case where the adjacent cars are in the same direction and the case where the adjacent cars are in the opposite direction. Such a configuration can allow a point at which the cars are reversed in a train to be automatically detected.

[0039] Though in the present embodiment the configuration for the connection is assumed to follow the rule where port Pl is used for the connection with the car on the front side and port P2 is used for the connection with the car on the rear side when the switching hubs in adjacent cars are connected, the invention is not limited to such a configuration, and the switching hubs in adjacent cars may be connected in accordance with other rules for connection that can determine whether or not these adjacent cars are in the same direction.

[0040] In addition, the train car network system according to the present embodiment has cameras (12, 13, ... 42 and 43) that are provided on either side of the respective cars and a monitor (15) for displaying the images taken by the cameras in the respective cars. This monitor is formed in such a manner that the cameras for taking an image are selected on the basis of the points at which the cars are reversed that have been detected by the central unit, and the images that have been taken by these cameras are displayed on the monitor. More concretely, the above-described monitor specifies the cameras that are provided on the side where the doors are open for each car on the basis of the points at which the cars are reversed that have been detected by the central unit, and is formed so as to display the images taken by these cameras.

As a result, the images taken by the cameras in each car on the side where the doors are open can be displayed on a monitor in a train that is formed of cars of which the direction is reversed in the middle.

[0041] In the present embodiment, the network relays according to the present invention are realized by the switching hubs (11, 21, 31 and 41), the detection device according to the present invention is realized by the central unit (14), and the display control unit according to the present invention is realized by the monitor (15) .

Here, the configuration including the system and the devices according to the present invention is not necessarily limited to the one that is described above, and various other configurations may be used. For example, the display control unit according to the present invention may be realized by the central unit (14) .

[0042] Though in the above embodiment the point at which the cars are reversed that has been detected is used to identify the images of the cameras that are used for the display where the area of the screen is divided, the point at which the cars are reversed may be used for other applications. For example, the speakers that are used for the announcement in the cars may be controlled in accordance with the point at which the cars are reversed. Typically, in a configuration where speakers are installed on either side within each car, the announcement within a car may be carried out using the speakers only on the side where the doors are open, or the volume of the speakers may be controlled so as to be louder on the side where the doors are

open than	on	the side where	the	doors are not open.
[0043]	It	is	also possible	for	the invention to be	applied in a
method	or	a	system where	the	process according to	the present

invention is carried out, a program for implementing such a method or system, or in a recording medium for storing such a program.

For example, the central unit may be realized by running a predetermined program in a computer that has hardware resources such as a processor or a memory. That is to say, the central unit may be realized by allowing the processor in a computer to read out a program onto a memory that is recorded in a data storage device such as a hard disk or a flash memory in order to run the program.

INDUSTRIAL APPLICABILITY [0044] The present invention can be applied in various train car network systems that are formed by connecting network relays installed in the respective cars that form a train.

REFERENCE SIGNS LIST [0045] VI through V4 car

11,	21, 31,	41 switching hub
12,	13, 22,	23, 32, 33, 42, 43 camera
14	central	unit
15	monitor

Claims

CLAIMS [1] A train car network system formed by connecting network relays that are installed for a plurality of cars, characterized in that the train car network system comprises a detection device for detecting a point at which cars are reversed through communication with the network relay in each car, the network relay in each car has a plurality of ports for connection with other devices, and the detection device acquires, from the network relay in each car, an address value for identifying the network relay, an address value of another network relay that is connected to the network relay, and a port number for identifying the port that is used for the connection, and detects the point at which cars are reversed on the basis of the relationship of the ports used for the connection between the network relays in adjacent cars, which is specified by the address values and the port numbers that have been acquired.
[2] The train car network system according to claim 1, further comprising :

cameras provided on the respective sides of each car;

a monitor for displaying images that are taken by cameras in each car; and a display control unit for controlling a display on the monitor, characterized in that the display control unit selects a camera for acquiring the image on the basis of the point at which cars are reversed that has been detected by the detection device and allows the image taken by the selected camera to be displayed on the monitor.
[3] A method for detecting a point at which cars are reversed , in a train car network system that is formed by connecting network relays installed for a plurality of cars, characterized in that the network relay in each car has a plurality of ports for a connection with another device, a detection device that is connected to communicate with the network relay in each car acquires, from the network relay in each car, an address value for identifying the network relay, an address value for another network relay that is connected to the network relay, and a port number for identifying the port that is used for the connection, and detects the point at which cars are reversed on the basis of the relationship of the ports used for the connection between the network relays in adjacent cars, which is specified by the address values and the port numbers that have been acquired.