JP2015122575A - Communication system and method for managing backup data - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a communication system capable of, as an example, stably managing backup data in a unitary manner.SOLUTION: The communication system comprises, as an example, a plurality of first relay devices and a second relay device. The plurality of first relay devices are dispersedly installed in homes in a local community area and are configured to relay first communication data in respective home systems installed in the respective homes to a predetermined network. The second relay device is installed on a communication carrier side corresponding to the local community area and is configured to relay second communication data for the communication carrier side to the network. Each of the plurality of first relay devices includes a control unit for transmitting backup data of that device to the second relay device through the network. The second relay device includes a management table for managing backup data transmitted from each of the plurality of first relay devices.

Description

  Embodiments described herein relate generally to a communication system and a backup data management method.

  Conventionally, a communication system such as a telephone system using the Internet is known. Such a communication system includes two different types of relay apparatuses connected via a network such as the Internet. As the two types of relay apparatuses, for example, a first relay apparatus such as a VoIP adapter installed in a company office or a private house, and a second relay apparatus such as a VoIP server installed on the telecommunications carrier side, Is mentioned.

JP 2005-79930 A

  In the above technology, as an example, the backup data of the first relay device installed in the house where power supply is likely to become unstable due to power failure or human error, etc. It is desirable that the backup data can be stably and centrally managed by transmitting to the second relay device installed in the network.

  As an example, the communication system according to the embodiment includes a plurality of first relay devices and second relay devices. The plurality of first relay apparatuses are distributed and installed in each home in one area area, and are configured to relay the first communication data in various home systems installed in each home to a predetermined network. Yes. The second relay device is installed on the telecommunications carrier side corresponding to the regional area, and is configured to relay the second communication data on the telecommunications carrier side to the network. Each of the plurality of first relay apparatuses includes a control unit that transmits its backup data to the second relay apparatus via the network. The second relay device has a management table for managing backup data transmitted from each of the plurality of first relay devices.

FIG. 1 is a schematic diagram illustrating an example of the overall configuration of the communication system according to the present embodiment. FIG. 2 is a schematic diagram illustrating an example of the relationship between the IP adapter device and the IP relay switching device according to the present embodiment. FIG. 3 is a diagram showing an example of a management table used by the IP relay switching apparatus according to the present embodiment. FIG. 4 is a block diagram showing an example of the internal configuration of the IP adapter device according to the present embodiment. FIG. 5 is a flowchart showing an example of the processing flow of the IP adapter device when the IP adapter device according to the present embodiment determines the backup destination of the backup data. FIG. 6 is a flowchart showing an example of the processing flow of the IP adapter device when the IP adapter device according to the present embodiment selects backup data. FIG. 7 is a flowchart showing an example of the processing flow of the IP adapter device when the IP adapter device according to the present embodiment performs backup. FIG. 8 is a sequence diagram illustrating an example of a processing flow of the entire communication system when the IP adapter device according to the present embodiment periodically backs up. FIG. 9 is a sequence diagram illustrating an example of a processing flow of the entire communication system when the IP adapter device according to the present embodiment performs backup according to the result of the memory diagnosis. FIG. 10 is a sequence diagram illustrating an example of a processing flow of the entire communication system when the IP adapter device according to the present embodiment performs backup based on a user instruction. FIG. 11 is a sequence diagram illustrating an example of a processing flow of the entire communication system when the IP adapter device according to the present embodiment synchronizes data with the IP relay switching device.

  Hereinafter, embodiments will be described with reference to the drawings.

  First, an example of the configuration of the communication system 1000 according to the present embodiment will be described with reference to FIGS.

  As illustrated in FIG. 1, the communication system 1000 includes an IP (Internet Protocol) adapter device 100 and an IP relay switching device 200. The IP adapter device 100 and the IP relay switching device 200 are connected to each other via an IP network communication network 300 so as to communicate with each other. The IP adapter device 100 is installed in the house, and the IP relay switching device 200 is installed on the telecommunications carrier side. The IP adapter device 100 and the IP relay switching device 200 are examples of a “first relay device” and a “second relay device”, respectively.

  The IP adapter device 100 includes companies such as a private branch exchange (PBX) 151 having a plurality of extension terminals 51, a POS (Point of sale) system 152, a security system 153, and a gas meter monitoring system 154. Various home systems installed in offices and private houses are connected. The IP adapter device 100 is connected to a maintenance terminal 400 for performing maintenance of the IP adapter device 100. The maintenance terminal 400 is an example of a “setting unit”.

  The IP relay switching apparatus 200 is connected to a mobile communication base station 250 that performs wireless communication with the mobile terminal 52. A network monitoring device 500 is connected to the IP adapter device 100 and the IP relay switching device 200 via the IP network communication network 300. The network monitoring device 500 is provided for remotely monitoring the IP adapter device 100 and the IP relay switching device 200.

  In the present embodiment, as shown in FIG. 2, a plurality of IP adapter devices 100 are installed in a distributed area. In the example shown in FIG. 2, five IP adapter devices 101A to 105A are dispersedly installed in the regional area A, and five IP adapter devices 101B to 105B are dispersedly installed in the regional area B. In the area C, four IP adapter devices 101C to 104C are distributed and installed. Each IP adapter device 100 is configured to relay the first communication data in various home systems 151 to 154 (see FIG. 1) installed in each area to the IP network communication network 300 (see FIG. 1). Yes.

  In the present embodiment, as shown in FIG. 2, only one IP relay switching apparatus 200 is installed in one regional area. In the example shown in FIG. 2, one IP relay switching apparatus 200A is installed in the area A, one IP relay switching apparatus 200B is installed in the area B, and one IP relay switching is installed in the area C. An apparatus 200C is installed. Each IP relay switching apparatus 200 is configured to relay the second communication data in the mobile communication base station 250 (see FIG. 1) corresponding to each regional area to the IP network communication network 300 (see FIG. 1).

  In the present embodiment, the IP relay switching apparatus 200 is configured to manage a plurality of IP adapter apparatuses 100 installed in the same area as the group. For example, in the example shown in FIG. 2, the IP relay switching apparatus 200A is configured to manage the IP adapter apparatuses 101A to 105A, and the IP relay switching apparatus 200B is configured to manage the IP adapter apparatuses 101B to 105B. The IP relay switching apparatus 200C is configured to manage the IP adapter apparatuses 101C to 104C.

  Here, in the present embodiment, the IP adapter device 100 is configured to be able to transmit its backup data to the IP relay switching device 200 via the IP network communication network 300. The IP relay switching apparatus 200 is configured to manage backup data of the IP adapter apparatus 100 using a management table 201 as shown in FIG.

  As shown in FIG. 3, in the management table 201, an IP relay exchange apparatus ID, an IP adapter apparatus ID, an installation location, statistical information, program information, and a backup capacity are registered.

  The IP relay switching device ID is information for identifying the IP relay switching device 200 that holds the management table 201. The IP adapter device ID is information for identifying the IP adapter device 100 under the management of the IP relay switching device 200. The installation location is information indicating where the IP adapter device 100 is installed in a regional area.

  The statistical information includes a CPU load rate and a memory usage rate. The CPU load factor is information indicating a load applied to a CPU included in a control unit 15 (see FIG. 4) described later of the IP adapter device 100. The memory usage rate is information indicating a usage rate of a memory unit 16 (see FIG. 4) described later of the IP adapter device 100.

  The program information is information indicating the version of the computer program used by the IP adapter device 100. The backup capacity is information indicating the backup data capacity of the IP adapter apparatus 100 managed by the IP relay switching apparatus 200.

  In the present embodiment, the management table 201 is configured to be accessible from the network monitoring apparatus 500 connected to the IP relay switching apparatus 200 via the IP network communication network 300. As a result, the user monitors information such as how much backup data of which IP adapter device 100 the IP relay switching device 200 holds by browsing the management table 201 using the network monitoring device 500. Can do.

  Next, an example of the internal configuration of the IP adapter device 100 will be described with reference to FIG.

  As shown in FIG. 4, the IP adapter device 100 includes a power supply unit 11, a line I / F (interface) unit 12, an IP communication I / F unit 13, a packet generation unit 14, a control unit 15, a memory The unit 16 and the external memory device 17 are mainly provided. The memory unit 16 and the external memory device 17 are examples of “storage unit”.

  The power supply unit 11 supplies power to each unit of the IP adapter device 100. The line I / F unit 12 functions as an interface for connecting the IP adapter apparatus 100 to the various home systems 151 to 154 shown in FIG. The IP communication I / F unit 13 functions as an interface for connecting the IP adapter device 100 to the IP network communication network 300. The packet generation unit 14 generates a communication packet used for communication via the IP network communication network 300.

  The control unit 15 includes a CPU that executes a computer program for controlling each unit of the IP adapter device 100. The memory unit 16 and the external memory device 17 store various data used by the IP adapter device 100.

  In the present embodiment, the control unit 15 performs a process of transmitting data stored in the memory unit 16 or the external memory device 17 to the IP relay switching apparatus 200 via the IP communication I / F unit 13. The backup data of the IP adapter device 100 can be stored in the IP relay switching device 200.

  Here, when the IP adapter device 100 is restarted in response to recovery from a power failure, or when the failed IP adapter device 100 is replaced with a new IP adapter device 100, the backup stored in the IP relay switching device 200 is used. It is necessary to restore the data of the IP adapter device 100 by synchronizing with the data. In particular, when the failed IP adapter device 100 is replaced with a new IP adapter device 100, the same order setting as the previous IP adapter device 100 is performed on the new IP adapter device 100, or the new IP adapter device 100 is set. Thus, it is necessary to appropriately take over between devices by installing a computer program of the same version as the previous IP adapter device 100.

  Therefore, in the present embodiment, the control unit 15 is configured to request the IP relay switching apparatus 200 to transmit backup data when receiving an instruction from the user via the maintenance terminal 400. ing. And the control part 15 is comprised so that the various data used by the IP adapter apparatus 100 may be recovered based on the backup data transmitted from the IP relay switching apparatus 200 in response to the request.

  As a backup destination of the backup data, in addition to the IP relay switching apparatus 200, a memory unit 16 (external memory device 17) provided in the IP adapter apparatus 100 may be considered.

  Therefore, in the present embodiment, the control unit 15 determines based on the first condition whether the backup destination of the backup data is the IP relay switching device 200 or the memory unit 16 (external memory device 17). It is configured as follows. The first condition is set by the maintenance terminal 400 based on a user operation.

  The first condition is set based on the use, importance, and data amount of backup data. For example, important backup data that is highly required to be redundant, backup data that is desired to be centrally monitored on the IP relay switching apparatus 200 side, backup data with a large amount of data, and long-term storage are required. Regarding the backup data and the like, the first condition can be set so that the IP relay switching apparatus 200 can manage it centrally. In this case, backup data that is less required to be redundant, backup data that can be monitored by logging into the IP adapter device 100 individually, backup data with a small amount of data, backup data with a short storage period, and the like The first condition can be set so as to be managed on the IP relay switching apparatus 200 side.

  In the present embodiment, the control unit 15 determines which data among the various data used by the IP adapter device 100 is the backup data based on the second condition set by the maintenance terminal 400. It is configured as follows.

  Similar to the first condition, the second condition is also set based on the use and importance of the data. For example, industrial order (function) setting data, error log at the time of failure, event trace information, statistical information, latest program file, communication record information, billing information, answering record data, announcement voice In addition, data according to the use of various home systems 151 to 154 (see FIG. 1) connected to the IP adapter device 100 is relatively high in importance. Therefore, when the above data is included in various data used by the IP adapter device 100, the second condition can be set so that the above data is selected as backup data.

  The backup processing may be performed based on automatic control of the control unit 15 as shown in FIGS. 8 and 9 described later, or via the maintenance terminal 400 as shown in FIG. 10 described later. It may be performed based on a user's manual instruction.

  That is, in the present embodiment, the control unit 15 may be configured to periodically perform backup processing based on time measurement by a timer (not shown), as shown in FIG. In the present embodiment, as shown in FIG. 9 to be described later, the control unit 15 performs memory diagnosis including measurement of the amount of data stored in the memory unit 16 using a timer (not shown). It may be configured to perform backup processing periodically when it is determined that the memory usage rate has reached a predetermined value or more. In the present embodiment, the conditions regarding the start timing of such backup processing are set by the maintenance terminal 400 based on the user's operation.

  Next, an example of a processing flow of the IP adapter device 100 when the IP adapter device 100 according to the present embodiment determines a backup destination of backup data will be described with reference to FIG.

  In this processing flow, as shown in FIG. 5, first, in step S1, processing for determining whether or not the backup data satisfies the first condition is executed. More specifically, whether the backup data is important data that is highly required to be redundant or whether there is a request for centralized monitoring on the IP relay switching apparatus 200 side. Then, a process for determining whether or not the data amount is large and whether or not the data requires long-term storage is executed.

  If it is determined in step S1 that the backup data satisfies the first condition, the process proceeds to step S2. In step S2, the backup destination is set in the IP relay switching apparatus 200, and the process returns.

  On the other hand, if it is determined in step S1 that the backup data does not satisfy the first condition, the process proceeds to step S3. In step S3, a process of setting the backup destination in the memory unit 16 or the external memory device 17 of the IP adapter device 100 is performed, and the process returns.

  Next, an example of a processing flow of the IP adapter device 100 when the IP adapter device 100 according to the present embodiment selects backup data will be described with reference to FIG.

  In this processing flow, as shown in FIG. 6, first, in step S11, processing for determining whether or not there is data satisfying the second condition among various data used in the IP adapter device 100 is executed. Is done. Specifically, among the various data used in the IP adapter device 100, industrial order (function) setting data, error log at the time of failure occurrence, event trace information, statistical information, the latest program file, Whether there is communication record information, billing information, answering record data, announcement voice, data according to the use of various in-home systems 151 to 154 (see FIG. 1) connected to the IP adapter device 100, etc. The process of determining is executed.

  If it is determined in step S11 that there is data satisfying the second condition, the process proceeds to step S12. In step S12, a process of selecting data satisfying the second condition as backup data is executed, and the process returns.

  On the other hand, if it is determined in step S11 that there is no data satisfying the second condition, the process returns without performing the process of selecting backup data as in step S12.

  Next, an example of a processing flow of the IP adapter device 100 when the IP adapter device 100 according to the present embodiment performs backup will be described with reference to FIG.

  In this processing flow, as shown in FIG. 7, first, in step S21, processing for determining whether or not the backup start conditions are met is executed. Specifically, whether or not the regular backup start timing has come, whether or not the usage rate of the memory unit 16 has reached a predetermined value or more, and an instruction that the user starts backup via the maintenance terminal 400 It is determined whether or not it has been performed.

  The process of step S21 is repeated until it is determined that the backup start conditions are met. If it is determined in step S21 that the backup start conditions are met, the process proceeds to step S22.

  Next, in step S22, processing for starting backup is executed. Specifically, a process of starting to back up the data selected as the backup target by the process flow shown in FIG. 6 to the backup destination determined by the process flow shown in FIG. 5 is executed. Then, the process proceeds to step S23.

  Next, in step S23, a process for determining whether or not the backup started in step S22 is completed. The process of step S23 is repeated until it is determined that the backup is completed. If it is determined in step S23 that the backup has been completed, the process returns.

  Next, an example of a processing flow of the entire communication system 1000 when the IP adapter device 100 according to the present embodiment periodically performs backup will be described with reference to FIG.

  In the example illustrated in FIG. 8, first, the IP adapter device 100 transmits a request for registering a backup to the IP relay switching device 200 in step S31. This request is made when a timer (not shown) that times the timing of regular backup times out a predetermined set value. Then, the IP adapter device 100 transfers the backup data to the IP relay switching device 200 in step S32.

  When the data transfer in step S32 is completed, the IP relay switching apparatus 200 stores the transferred data and updates the management table 201 (see FIG. 3) in step S33. In step S34, the IP relay switching apparatus 200 transmits a response indicating that the backup has been registered to the IP adapter apparatus 100.

  Upon receiving the response in step S34, the IP adapter device 100 resets a timer (not shown) that measures the timing of regular backup in step S35. Thereby, timing for the next regular backup is started.

  Next, another example of the processing flow of the entire communication system 1000 when the IP adapter device 100 according to the present embodiment performs backup according to the result of the memory diagnosis will be described with reference to FIG.

  In the example shown in FIG. 9, first, the IP adapter apparatus 100 transmits a request for registering a backup to the IP relay switching apparatus 200 in step S41. This request is made when it is determined by the memory diagnosis periodically performed by the IP adapter device 100 that the memory usage rate exceeds a predetermined value. Then, the IP adapter device 100 transfers the backup data to the IP relay switching device 200 in step S42.

  When the data transfer in step S42 ends, the IP relay switching apparatus 200 stores the transferred data in step S43 and updates the management table 201 (see FIG. 3). In step S44, the IP relay switching apparatus 200 transmits a response indicating that the backup has been registered to the IP adapter apparatus 100.

  Upon receiving the response in step S44, the IP adapter device 100 resets a timer (not shown in FIG. 4) that times the timing of memory diagnosis in step S45. As a result, timing for the next memory diagnosis is started. Then, when a timer (not shown) that times the timing of memory diagnosis measures a predetermined set value and times out, the IP adapter device 100 executes memory diagnosis in step S46, and the memory usage rate is equal to or higher than the predetermined value. It is determined whether or not.

  Next, an example of a processing flow of the entire communication system 1000 when the IP adapter apparatus 100 according to the present embodiment performs backup based on a user instruction will be described with reference to FIG.

  In the example illustrated in FIG. 10, first, the maintenance terminal 400 transmits an instruction to start backup to the IP adapter device 100 in step S51. This instruction is performed based on the operation of the maintenance terminal 400 by the user. For example, the user operates the maintenance terminal 400 to transmit the instruction in step S51 to the IP adapter device 100 when it is known in advance that a power outage such as a planned power outage will occur.

  Upon receiving the instruction in step S51, the IP adapter apparatus 100 transmits a request for registering the backup to the IP relay switching apparatus 200 in step S52. Then, the IP adapter device 100 transfers the backup data to the IP relay switching device 200 in step S53.

  When the data transfer in step S53 is completed, the IP relay switching apparatus 200 stores the transferred data and updates the management table 201 (see FIG. 3) in step S54. In step S55, the IP relay switching apparatus 200 transmits a response indicating that the backup has been registered to the IP adapter apparatus 100.

  Upon receiving the response in step S55, the IP adapter device 100 transmits a notification that the backup has been completed to the maintenance terminal 400 in step S56. As a result, the user is notified via the maintenance terminal 400 that the backup has been completed.

  Next, an example of a processing flow of the entire communication system 1000 when the IP adapter apparatus 100 according to the present embodiment performs data synchronization with the IP relay switching apparatus 200 will be described with reference to FIG.

  In the example illustrated in FIG. 11, first, the maintenance terminal 400 transmits an instruction to start data synchronization to the IP adapter device 100 in step S61. This instruction is performed based on the operation of the maintenance terminal 400 by the user. For example, when the IP adapter device 100 is restarted in response to recovery from a power failure, or when the failed IP adapter device 100 is replaced with a new IP adapter device 100, the user instructs the IP adapter device 100 to perform the instruction in step S61. The maintenance terminal 400 is operated so as to transmit to the terminal.

  Upon receiving the instruction in step S61, the IP adapter apparatus 100 transmits a request to the IP relay switching apparatus 200 to transfer the data that the IP relay switching apparatus 200 previously stored as a backup of the IP adapter apparatus 100 in step S62. To do.

  Upon receiving the request in step S62, the IP relay switching apparatus 200 searches for backup data of the IP adapter apparatus 100 in step S63. The IP relay switching apparatus 200 transfers the data found by the search to the IP adapter apparatus 100 in step S64. When the data transfer is completed, the IP relay switching apparatus 200 transmits a response indicating that the data transfer is completed to the IP adapter apparatus 100 in step S65.

  Upon receiving the response in step S65, the IP adapter device 100 synchronizes data based on the transferred data in step S66. That is, the backup data transferred from the IP relay switching apparatus 200 is used to recover its own data. When the data synchronization is completed, the IP adapter device 100 transmits a notification that the data synchronization is completed to the maintenance terminal 400 in step S67. Thereby, the user is notified via the maintenance terminal 400 that the data synchronization is completed.

  As described above, in the present embodiment, each of the plurality of IP adapter devices 100 is configured to be able to transmit its own backup data to the IP relay switching device 200 via the IP network communication network 300. ing. The IP relay switching apparatus 200 is configured to manage backup data received from each of the plurality of IP adapter apparatuses 100 using the management table 201. As a result, the backup data of the IP adapter device 100 installed in the house where the power supply is likely to become unstable due to a power failure or a human error, etc. is replaced with the IP relay exchange installed on the telecommunications carrier side that is likely to obtain a stable power supply. Management can be performed using the management table 201 on the apparatus 200 side. As a result, the backup data of the IP adapter device 100 can be stably and centrally managed on the IP relay switching device 200 side.

  In the present embodiment, as described above, the control unit 15 of the IP adapter device 100 sets the backup destination of the backup data to the IP relay switching device 200 or the IP adapter device 100 itself (the memory unit 16 and the external memory). The device 17) is determined based on the first condition set by the maintenance terminal 400. Thereby, by setting various first conditions using the maintenance terminal 400, an appropriate backup destination can be selected according to, for example, the use, importance, and data amount of the backup data.

  In the present embodiment, as described above, the control unit 15 of the IP adapter device 100 sets which data among the various data used by the IP adapter device 100 is the backup data by the maintenance terminal 400. The second condition is determined based on the second condition. Thus, by setting the second condition in various ways using the maintenance terminal 400, it is possible to select appropriate backup data according to, for example, the use and importance of the data.

  In the present embodiment, as described above, the control unit 15 of the IP adapter device 100 is configured to transmit backup data to the IP relay switching device 200 at the timing set by the maintenance terminal 400. Thus, by setting various backup start timings using the maintenance terminal 400, backup can be automatically performed at an appropriate timing.

  In the present embodiment, as described above, the control unit 15 of the IP adapter apparatus 100 receives an instruction from the user via the maintenance terminal 400 to synchronize data with the IP relay switching apparatus 200. In addition, the IP relay switching apparatus 200 is configured to make a request for transmitting backup data. And the control part 15 is comprised so that the various data used by the IP adapter apparatus 100 may be recovered based on the backup data transmitted from the IP relay switching apparatus 200 in response to the request. Thereby, when the IP adapter device 100 is restarted in response to recovery from a power failure, or when the failed IP adapter device 100 is replaced with a new IP adapter device 100, an instruction to synchronize data is given to the maintenance terminal 400. The IP adapter device 100 can be easily restored simply by using

  As mentioned above, although embodiment of this invention was described, the said embodiment is an example to the last, Comprising: It is not intending limiting the range of invention. The above embodiment can be implemented in various forms, and various omissions, replacements, and changes can be made without departing from the spirit of the invention. The above-described embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and equivalents thereof.

15 Control unit 16 Memory unit (storage unit)
17 External memory device (storage unit)
100 IP adapter device (first relay device)
151-154 Home System 200 IP Relay Exchange Device (Second Relay Device)
201 management table 300 IP network communication network 400 maintenance terminal (setting means)
1000 Communication system

Claims (6)

A plurality of first relay devices that are distributed and installed in each home in one area area and relay first communication data of various home systems installed in each home to a predetermined network;
A second relay device that is installed on a telecommunications carrier side corresponding to the regional area and relays the second communication data on the telecommunications carrier side to the network;
Each of the plurality of first relay devices includes a control unit that transmits its backup data to the second relay device via the network,
The communication system, wherein the second relay device includes a management table for managing the backup data transmitted from each of the plurality of first relay devices. Each of the plurality of first relay devices further includes a storage unit capable of storing the backup data,
The control unit is configured to determine whether the backup destination of the backup data is the second relay device or the storage unit based on a first condition set by a setting unit. The communication system according to claim 1.   The control unit is configured to determine which of the various data used by the first relay device is the backup data based on the second condition set by the setting unit. The communication system according to claim 1 or 2.   The communication system according to any one of claims 1 to 3, wherein the control unit is configured to transmit the backup data to the second relay device at a timing set by a setting unit.   When the control unit receives an instruction from a user via a setting unit, the control unit requests the second relay device to transmit the backup data, and responds to the request to the second relay device. The communication system according to any one of claims 1 to 4, wherein the communication system is configured to recover various data used by the first relay device based on the backup data transmitted from the network. From each of a plurality of first relay devices that are distributed and installed in each home in one local area and relay the first communication data of various home systems installed in each home to a predetermined network. The backup data is transmitted to the second relay device that is installed on the corresponding communication carrier side and relays the second communication data on the communication carrier side to the network.
A backup data management method for managing the backup data transmitted from each of the plurality of first relay apparatuses using a management table of the second relay apparatus.

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