JPH09331401A - Line terminal equipment - Google Patents

Abstract

(57) Abstract: There is provided a line terminal device capable of reducing the communication error occurrence rate without waste of end waiting time during through wireless communication, waste of recall, and the like. SOLUTION: A plurality of data terminal devices are connected to a public line 4 through wireless communication via wireless communication in response to an instruction of a message from a central monitoring device 5, and one data terminal device selected by a start request message is public. In the line terminal device 1 having the line control means 23 for controlling to communicate with the central monitoring device 5 via the line 4, a wireless message reception analysis means 24 for receiving and analyzing a message at the time of through wireless communication connection, and its analysis. When the message analyzed by the wireless message receiving / analyzing means 24 is the communication end message from the central monitoring device 5, the communication controlling means 25 controls communication through the through wireless communication connection. Line control means 2
The connection is switched to No. 3, and the telegram from the central monitoring device 5 following the communication end telegram is received.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a line terminal device for controlling data transfer between a data terminal device connected wirelessly and a central monitoring device via a public line.

[0002]

2. Description of the Related Art In recent years, a no-ringing communication service using an existing public line and a data transfer to a central monitoring device and a home controller by a terminal calling system have been studied, and a high efficiency of a line terminal device used for it has been required. It

A conventional line terminal device will be described below with reference to the drawings. FIG. 5 is a block diagram showing the configuration of a conventional line terminal device. In the figure, reference numeral 1 is a line terminal device for selectively connecting the first data terminal device 2 and the second data terminal device 3 wirelessly and controlling the connection to the central monitoring device 5 via the public line 4. Here, the first data terminal device 2 and the second data terminal device are automatic gas cutoff devices with a wireless communication device having a built-in microcomputer, and are connected to a gas meter to measure a gas flow rate and detect an abnormality. Then, the supply of gas is cut off, and the meter reading value and the reason for cutoff are wirelessly communicated with the line terminal device 1 and data is transferred to the central monitoring device 5 via the public line 4. However, it goes without saying that the number of data terminal devices is not limited to this, and the number of data terminal devices is not limited to two.

Reference numeral 6 denotes an antenna for wirelessly connecting the line terminal device 1 to the first data terminal device 2 and the second data terminal device 3, and 7 denotes the first data terminal device 2 via the antenna 6 of the line terminal device 1. Alternatively, a wireless interface unit for wirelessly communicating with the second data terminal device 3, 8 is a network control unit for matching the electrical conditions between the line terminal device 1 and the public line 4, and 9 is the public line 4 for the line terminal device 1 Switch for switching connection from the data terminal device side to the data terminal device side, 10 is a receiving unit that receives a signal from the central monitoring device 5 via the changeover switch 9, and 11 is a message for analyzing the content of the received message. An analysis unit, 12 is a transmission message forming unit that generates a transmission message to be transmitted from the line terminal device 1, 13 is a transmission unit that transmits the transmission message, and 14 is a wireless switching unit that controls switching of the changeover switch. A. The change-over switch 9 is normally a contact on the side of the line terminal device 1, that is, on the A side in the figure.

The communication protocol in the above configuration will be described. In this type of line terminal device 1, the central monitoring device 5 outputs an activation request message, and the line terminal device 1 connects the data terminal device to the public line 4 via wireless communication in response to the activation request message. Finally, a communication end message is generally output from the selectively connected data terminal device to end the communication.

[0006] First, the line terminal device 1 is called from the central monitoring device 5 by no ringing incoming call, and the network control unit 8 matches the electrical condition with the public line 4 to enable communication with the central monitoring device 5. The receiving unit 10 receives a telegram from the central monitoring device 5, the telegram analyzing unit 11 analyzes the telegram, and the wireless switching unit 14 controls switching of the changeover switch 9 in response to the instruction of the telegram.

When the central monitoring device 5 communicates with the line terminal device 1, the line terminal device 1 is called with no ringing incoming, and then a message to the line terminal device 1 is given. The line terminal device 1 corresponds to the received message and the transmission message composition unit 1
2, a response message is generated, and the response message is transmitted from the transmission unit 13 to communicate with the central monitoring device 5.

When the central monitoring device 5 communicates with the first data terminal device 2, the central monitoring device 5 first calls the line terminal device 1 with no ringing, and then transmits a start request message to the data terminal device. To do. The line terminal device 1 receives the message by the receiving unit 10, and the message analyzing unit 11 receives the message.
Analyze the contents of the message. When the message is analyzed as a start request message for the first data terminal device 2, the wireless switch control unit 14 switches the contact of the changeover switch 9 from the A contact side to the B contact side, and the wireless interface unit 7
In this way, a message for the first data terminal device 2 is generated, converted into a radio signal, and output from the antenna 6 as a radio wave.
After that, the central monitoring device 5 and the first data terminal device 2 can communicate with each other via the public line 4, the network control unit 8, the changeover switch 9, the wireless terminal interface unit 7, and the antenna 6. This wireless connection is also a means for selecting one of the plurality of data terminal devices.

On the other hand, when the message received by the receiving unit 10 is analyzed by the message analyzing unit 11 and the message is a start request message for the second data terminal device 3, the wireless switch control unit 14 causes the contact of the changeover switch 9 to be an A contact. Side to the B contact side, the wireless terminal interface unit 7 generates a telegram for the second data terminal device 3 and converts it into a wireless signal,
By outputting as radio waves from the antenna 6,
Communication between the central monitoring device 5 and the second data terminal device 3 becomes possible.

FIG. 6 is a protocol diagram showing the operation when the central monitoring device 5 communicates with the first data terminal device 2 in the above conventional example. The arrow in the figure indicates the direction in which a message is sent. First, the central monitoring device 5 calls the line terminal device 1 by receiving no ringing, and then calls the first terminal device.
The activation request message (1) for the data terminal device 2 is transmitted. The line terminal device 1 switches the changeover switch 9 to the B contact side in response to the telegram to establish a through wireless communication connection, and wirelessly connects via the wireless interface unit 7. After that, the telegrams (2), (3) and (4) are transferred between the central monitoring device 5 and the first data terminal device 2. Next, the central monitoring device 5 sends a communication end message (5) to the line terminal device 1 to end the communication with the first data terminal device 2. At this time, the changeover switch 9 is moved to the B contact side. Since it is switched to the through wireless communication connection state, the line terminal device 1
Cannot determine the end of communication, and transmits the message (6) to the first data terminal device 2 as a radio signal. After that, the communication is terminated by a message waiting timeout from the first data terminal device 2, the network control unit 8 disconnects the line with the central monitoring device 5, and terminates the communication. Therefore, in order for the central monitoring device 5 to select the other second data terminal device 3 for communication, the line terminal device 1 is called from the central monitoring device 5 again without ringing, and the second data terminal device 3 is selected. Message
Send (7) and start communication as above.

[0011]

In such a conventional line terminal device, the central monitoring device 5 is the first data terminal device 2.
Or, when any one of the second data terminal devices 3 is selected and communication is started, thereafter, a message transmitted from the central monitoring device 5 does not reach the receiving unit 10 of the line terminal device 1 and passes through the line terminal device 1. And continues to be sent to the selected data terminal device. Therefore, the line terminal device 1 cannot analyze the electronic message after shifting to the wireless communication with the selected data terminal device.

Therefore, the central monitoring device 5 sends a communication end message to the data terminal device to end the communication with the data terminal device in communication, but the line terminal device 1 cannot determine that the communication has ended. Therefore, the communication is terminated and the line is disconnected due to a message waiting timeout from the data terminal device during communication. At this time, since the communication between the line terminal device 1 and the data terminal device is wireless communication, the communication partner is unspecified or there is a limitation in the procedure of communication retry. Therefore, it is necessary to set the time for determining the time-out to be longer than that in the case of wired communication, the time for the line terminal device 1 to determine the end of communication is significantly long, and the wireless interface unit 7 requiring a large amount of power is required.
It was consuming useless power. Further, in order to communicate with other data terminal devices, there is a problem that the central monitoring device 5 must call the line terminal device 1 again with no ringing and start from the line connection.

When an error such as a parity occurs in a message transmitted from the data terminal device during communication to the central monitoring device 5, the path from the data terminal device to the line terminal device 1 is normal and the line terminal device is normal. If an error occurs in the route from 1 to the central monitoring device 5, the central monitoring device 5
In response to the resend request from the data terminal device, the message sent from the data terminal device must be transferred to the central monitoring device 5 again.
There has been a problem that an error may occur in the wireless path from the data terminal device to the line terminal device 1 this time and the communication error occurrence rate may deteriorate, or the communication time may increase due to the retry of wireless communication. Further, when an error occurs in the message transmitted from the central monitoring device 5 to the data terminal device, the route from the central monitoring device 5 to the line terminal device 1 is normal, and the route from the line terminal device 1 to the data terminal device is normal. When an error occurs, a message sent from the central monitoring device 5 has to be transferred to the data terminal device again in response to a resend request from the data terminal device 1. Therefore, in the route from the central monitoring device 5 to the line terminal device 1, This time, there was a problem that an error may occur and the communication error occurrence rate may deteriorate.

The present invention solves the above problems, and an object of the present invention is to provide a line terminal device capable of eliminating waste such as waiting time at the end of communication and waste of recall, and reducing the communication error occurrence rate. To do.

[0015]

According to a first aspect of the present invention, there is provided a wireless telegram reception analysis means for receiving and analyzing a telegram during a through wireless communication connection of a data terminal device to a public line.
A line terminal device provided with communication control means for controlling communication according to the analysis result.

With this, it is possible to immediately respond to the communication termination message of the central monitoring device. The present invention according to claim 2 provides, to the line terminal device according to claim 1, an upstream message storage unit for constantly updating and storing an upstream message from a data terminal device in communication, and an upstream transmitting unit for transmitting the stored message. Is provided, and the stored uplink message is transmitted to the central monitoring device in response to a retransmission request from the central monitoring device.

This makes it possible to prevent a new error from occurring in the path between the line terminal device and the data terminal device, reduce the communication error rate, and prevent the communication time from increasing.

The present invention according to claim 3 transmits, to the line terminal device according to claim 1, a downlink message storage unit for constantly updating and storing a downlink message from a central monitoring device during communication, and the stored message. A downlink terminal is provided, and the stored downlink message is transmitted to the data terminal device in response to a retransmission request from the data terminal device.

As a result, it is possible to prevent a new error from occurring in the path between the line terminal device and the central monitoring device and reduce the communication error occurrence rate.

[0020]

According to the first aspect of the present invention, the wireless message receiving / analyzing means means a means for intercepting and analyzing a message in the through wireless communication connection, and is constituted by a wireless message receiving section and a wireless message analyzing section. Each can be configured in the same manner as the receiving unit and the message analyzing unit in the conventional example. The interception analysis of this wireless message reception analysis means is limited to the through wireless communication connection,
In the embodiment, the public line connection in the line control means is connected immediately after the changeover switch for switching from the line control means to the wireless connection to the data terminal device. Further, the communication control means means means for controlling the line connection of the changeover switch in accordance with the analysis result of the wireless message reception analysis means, and the second wireless changeover control section for controlling the changeover switch and the interception. The communication control unit controls the second wireless switching control unit by a telegram. The communication control unit also relates to claims 2 and 3.

[0021] In claim 2, the upstream message storage means means for constantly updating and storing the upstream message from the intercepted data terminal device to the central monitoring device, and always stores the last upstream message. Prepare and store the data so that it can respond to a resend request from the central monitoring device. The communication control unit in the communication control means, in response to the resend request from the central monitoring device that has been intercepted, to output an upstream message to the upstream message storage unit,
The upstream transmission unit transmits to the central monitoring device.

In claim 3, the downlink message storage means means for constantly updating and storing the intercepted downlink message from the intercepted central monitoring device to the data terminal device, and always stores the last downlink message. The data is prepared and stored so that it can respond to a retransmission request from the data terminal device. The communication control unit in the communication control means causes the downlink message storage unit to output a downlink message in response to the intercepted retransmission request from the data terminal device, and causes the downlink transmission unit to transmit the message to the data terminal device.

Examples will be described below. (Embodiment 1) Hereinafter, Embodiment 1 of the line terminal device of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of this embodiment. The same components as those of the conventional example shown in FIG. 5 are assigned the same reference numerals and detailed explanations thereof will be omitted.

In the figure, reference numeral 15 is a wireless telegram receiving unit for inputting a signal from the B contact side of the changeover switch, receiving a signal transferred to the data terminal device via the wireless terminal interface unit 7 and converting it into a telegram, 16 Is the wireless message receiver 15
The wireless telegram analysis unit that analyzes the received telegram received in step 17, 17 is a communication control unit that performs communication control according to the information analyzed by the wireless telegram analysis unit 16, and 18 is a second wireless switching control unit.
During the through wireless communication connection between the central monitoring device 5 and the data terminal device, the electronic message received by the wireless electronic message receiving unit 15 is
As a result of the analysis by the wireless telegram analysis unit 16, when it is determined that the communication end telegram is reached, the changeover switch 9 is controlled to be switched so that the receiving unit 10 continuously receives the telegram transmitted from the central monitoring device 5.

The line terminal device of this embodiment also has the number 1
The blocks having the same configuration as in the conventional example are collectively referred to as a line control unit, and the wireless message receiving unit 15 and the wireless message analyzing unit 16 constitute a wireless message receiving and analyzing unit 24, and the communication control unit 17 is provided. The second wireless switching control unit 18 and the second wireless switching control unit 18 form a communication control unit 25.

Reference numeral 19 denotes an upstream message storage unit for storing the last upstream message received by the wireless message receiving unit 15 during the through wireless communication connection, and 20 denotes the message analyzed by the wireless message analyzing unit 16 as the central monitoring device 5. If it is a resend request message of
This is an upstream transmission unit that transmits the stored upstream message to the central monitoring device 5 if there is no abnormality in the message stored in the upstream message storage unit 19. Further, 21 is a downlink message storage unit for storing the last downlink message received by the wireless message receiving unit 15 during the through wireless communication connection, and 22 is the wireless message analyzing unit 1
If the telegram analyzed in 6 is the resend request telegram of the data terminal device, and if the telegram stored in the downlink telegram storage unit 21 is normal, the downlink transmission unit that transmits the stored downlink telegram to the data terminal device is there. The upstream message storage unit 19
An example in which the downlink transmission unit 22 is mounted will be described in Examples 2 and 3, and detailed description thereof will be omitted in this example. Further, the above-mentioned data terminal device means either the first data terminal device 2 or the second data terminal device 3 in this embodiment.

In the above configuration, the first data terminal device 2
Alternatively, a case of communicating with the second data terminal device 3 will be described as an example. In order to communicate with the first data terminal device 2, first,
It starts from calling the line terminal device 1 from the central monitoring device 5 by no ringing incoming call. The called line terminal device 1 is connected to the central monitoring device 5 by matching the electrical conditions with the public line 4 by the network control unit 8.

Since the changeover switch 9 is initially connected to the A contact side, the first electronic message transmitted from the central monitoring device 5 is received by the receiving section 10. The electronic message received by the receiving unit 10 is analyzed by the electronic message analyzing unit 11, and if the electronic message is for the line terminal device 1 itself, a response electronic message is generated by the transmitting electronic message forming unit 12 and is transmitted from the transmitting unit 13 to transmit the central monitoring device. 5 can be communicated with.

Next, the central monitoring device 5 transmits to the line terminal device 1 an activation request message for activating the data terminal device. The message is received by the receiving unit 10, and the message is analyzed by the message analyzing unit 11. When this message is analyzed as a start request message for the first data terminal device 2, the wireless switching control unit 14 switches the contact of the changeover switch 9 from the A contact side to the B contact side to control the wireless terminal interface unit 7. Then, the activation request message is converted into a wireless signal and the antenna 6
The central monitoring device 5 and the first data terminal device 2 are transmitted as radio signals from the public line 4, the network control unit 8, the changeover switch 9, the wireless terminal interface unit 7,
Wireless communication is possible via the antenna 6.

When the wireless communication is started, the wireless message receiver 15
Receives a signal transferred by the wireless terminal interface unit 7 and converts it into a message. The communication control unit 17 that performs communication control according to the information analyzed by the wireless telegram analysis unit 16 determines that the telegram received by the wireless telegram receiving unit 15 in the wireless communication transmitted from the central monitoring device 5 to the first data terminal device 2 is the wireless telegram. As a result of the analysis by the statement analysis unit 16, when it is determined that the communication end message is received, the second wireless switching control unit 18 sets the changeover switch 9 from the B contact side so that the reception unit 10 continuously receives the message sent from the central monitoring device 5. Switch to the A contact side.

FIG. 2 is a protocol diagram showing a communication sequence of the line terminal device 1 of this embodiment. The operation of the line terminal device 1 will be described with reference to FIG. 2 by the flow of a telegram. First, the central monitoring device 5 calls the line terminal device 1 by no ringing incoming call. Subsequently, the central monitoring device 5 selects the first data terminal device 2 by the message (1) and starts communication. Thereafter, the telegrams (2), (3) and (4) are transferred between the central monitoring device 5 and the selected first data terminal device 2.

Next, when the central monitoring device 5 wants to end the communication with the first data terminal device 2 and start the communication with the second data terminal device 3, first, the communication termination message ( 5) is transmitted, and subsequently, the activation request message (7) for the second data terminal device 3 is transmitted to the line terminal device 1. The line terminal device 1 converts the communication end message (5) to the first data terminal device 2 into a wireless signal and transfers the message (6), and the second wireless switching control unit 18 in the communication control means 25.
Thus, the changeover switch 9 is connected to the A contact side, and the following electronic message (7) is received by the receiving unit 10.

When the message (7) received by the receiving unit 10 is analyzed by the message analyzing unit 11 as a start request message for the second data terminal device 3, the wireless switching control unit 1
4, the contact of the changeover switch 9 is switched again from the A contact side to the B contact side, and the activation request message (8) is transmitted from the wireless terminal interface section 7 to the second data terminal device 3 via the antenna 6 as a radio signal. By
Wireless communication between the central monitoring device 5 and the second data terminal device 3 becomes possible.

Next, when the central monitoring device 5 wants to terminate the communication with the second data terminal device 3 and also terminates the communication with the line terminal device 1, the communication termination message (9 ) Is transmitted, and then the communication end message (11) for the line terminal device 1 is transmitted. When the line terminal device 1 receives the communication end message (9) to the second data terminal device 3, the second wireless switching control unit 18 in the communication control means 25.
Since the changeover switch 9 is connected to the A contact side by the above, the electronic message (11) transmitted from the central monitoring device 5 next is the receiving unit 1
When it is received at 0 and is analyzed by the electronic statement analysis unit 11 that the communication with the line terminal device 1 is completed, the network control unit 8 disconnects the line with the central monitoring device 5 and ends the communication.

As described above, according to the present embodiment, even if the wireless communication is started, the electronic message is intercepted and analyzed by the wireless electronic message reception / analysis means 24, and the line connection is controlled according to the analysis result. By doing so, it is possible to immediately end the wireless communication in response to the communication end request of the central monitoring device 5, reduce the communication time and power consumption, and return to the non-wireless communication to connect the line to the central monitoring device 5. In this state, the next message can be received to respond to the connection request to another data terminal device, and the central monitoring device 5 need not be recalled.

(Second Embodiment) A second embodiment of the line terminal device of the present invention will be described below with reference to FIG. The present embodiment is different from the first embodiment in that in FIG. 1, the uplink message storage unit 19 stores the wireless message reception unit 15 during the through wireless communication connection between the central monitoring device 5 and the first data terminal device 2.
The last upstream telegram of the first data terminal device 2 received by the first data terminal device 2 is stored in the first data terminal device 2 from the central monitoring device 5.
If the downlink message transmitted to the message is a retransmission request message as a result of analysis by the wireless message analysis unit 16, the uplink message storage unit 1
If there is no abnormality in the telegram stored in 9, the communication control unit 17 in the communication control unit 25 controls the up transmission telegram stored from the up transmission unit 20 to be transmitted to the central monitoring device 5, and also the up transmission telegram. If the electronic message stored in the storage unit 19 is abnormal, it means that an error has occurred in the electronic message between the first data terminal device 2 and the line terminal device 1. Therefore, a response from the first data terminal device 2 The purpose is to wait for a message and transfer it to the central monitoring device 5.

FIG. 3 is a protocol diagram showing a communication sequence of the line terminal device of this embodiment. According to the above configuration,
When transferring the message (3) of the first data terminal device 2, the first
If the path from the data terminal device 2 to the line terminal device 1 is normal, and a parity error occurs on the line from the line terminal device 1 to the central monitoring device 5, if a retransmission request (12) from the central monitoring device 5 can be confirmed. By transmitting the previously transmitted telegram (4) by the line terminal device 1, this retransmission processing prevents an error from occurring in the route from the first data terminal device 2 to the line terminal device 1 and lengthens the communication time. Can be prevented.

As described above, according to the present embodiment, the upstream message storage unit 19 stores the upstream message, and in response to the resend request from the central monitoring device 5, the stored upstream message is stored as long as there is no abnormality. Is transmitted from the upstream transmission unit 20 to the central monitoring device 5, a new error can be prevented from occurring, the communication error occurrence rate can be reduced, and the communication time can be prevented from becoming long.

(Third Embodiment) A third embodiment of the line terminal device of the present invention will be described below with reference to the drawings. FIG.
In this regard, the difference between the present embodiment and the second embodiment is that, during the through wireless communication connection between the central monitoring device 5 and the first data terminal device 2, the last received by the wireless message receiving unit 15 by the downstream wireless message storage unit 21. When the message from the first data terminal device 2 to the central monitoring device 5 is a retransmission request message as a result of being analyzed by the wireless message analyzing unit 16, it is stored in the downlink wireless message storage unit 21. If there is no abnormality in the transmitted message, the communication control unit 17 in the communication control means 25.
Controls the downlink transmission message stored in the downlink transmission unit 22 to be transmitted to the first data terminal device 2. If the message stored in the downlink message storage unit 21 is abnormal, the central monitoring device 5 Since an error has occurred in the telegram on the route to the line terminal device 1, the response telegram from the central monitoring device 5 is waited for, and it is transferred to the first data terminal device 2. .

FIG. 4 is a protocol diagram showing the communication sequence of the line terminal device 1 of this embodiment. According to the above configuration, when the message (5) of the central monitoring device 5 is transferred, the route from the central monitoring device 5 to the line terminal device 1 is normal, and the route from the line terminal device 1 to the first data terminal device 2 is If an error occurs in the message (6) at, the first data terminal device 2
Confirm the resend request message (13) from
By transmitting (6) from the line terminal device 1 to the first data terminal device 2, it is possible to prevent an error from occurring in the route from the central monitoring device 5 to the line terminal device 1 in this retransmission processing.

As described above, according to the present embodiment, the downlink message is stored in the downlink message storage unit 21, and in response to the retransmission request from the first data terminal device 2, there is no abnormality in the stored downlink message. By transmitting it from the downlink transmission unit 22 to the first data terminal device 2, it is possible to prevent the occurrence of a new error, reduce the communication error occurrence rate, and prevent the communication time from increasing. be able to.

[0043]

As is apparent from the above description, the present invention has the following effects.

According to the first aspect of the present invention, the telegram during the through wireless communication connection is intercepted, and the connection between the central monitoring apparatus and the data terminal apparatus is controlled according to the content of the telegram. When the communication end message is transmitted from the central monitoring device to the data terminal device, the wireless message reception analysis means can receive and analyze the message to determine that the communication has ended, so the data terminal device side ends with a message waiting timeout. It is possible to reduce unnecessary communication time and power consumption because there is no need to wait, and when a communication end message to the data terminal device is confirmed, the next is a communication message to the line terminal device. If connected, it is possible to subsequently select another data terminal device from the central monitoring device. Therefore, once the line terminal device is called from the central monitoring device, it is possible to communicate with a plurality of data terminal devices without disconnecting the line, and it is possible to reduce communication time and call charges.

According to the second aspect of the present invention, the upstream telegram from the data terminal device in communication is updated and stored, and the stored upstream telegram is stored in response to the retransmission request from the central monitoring device to the data terminal device. By sending it, the route from the data terminal equipment to the line terminal equipment is normal,
It is possible to prevent a new communication error from occurring in the route from the data terminal device to the line terminal device when retransmitting when an error occurs in the telegram on the route from the line terminal device to the central monitoring device. It is possible to reduce the communication time and prevent the communication time from increasing.

The present invention according to claim 3 updates and stores the downlink message from the central monitoring device during communication, and transmits the stored downlink message in response to a resend request from the data terminal device to the central monitoring device. By doing so, when the line from the central monitoring device to the line terminal device is normal and an error occurs in the message on the route from the line terminal device to the data terminal device, the line terminal device to the central monitoring device can be retransmitted. It is possible to prevent a new communication error from occurring in the path, and to reduce the communication error occurrence rate.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of first to third embodiments of a line terminal device of the present invention.

FIG. 2 is a protocol diagram showing the operation of the first embodiment of the line terminal device of the present invention.

FIG. 3 is a protocol diagram showing the operation of the second embodiment of the line terminal device of the present invention.

FIG. 4 is a protocol diagram showing the operation of the third embodiment of the line terminal device of the present invention.

FIG. 5 is a block diagram showing a configuration of a conventional line terminal device.

FIG. 6 is a protocol diagram showing the operation of the conventional example.

[Explanation of symbols]

 1 line terminal device 2 first data terminal device 3 second data terminal device 4 public line 5 central monitoring device 6 antenna 7 wireless interface unit 8 network control unit 9 changeover switch 10 receiving unit 11 telegram analysis unit 12 transmission telegram configuration unit 13 transmission Unit 14 wireless switching control unit 15 wireless message receiving unit 16 wireless message analysis unit 17 communication control unit 18 second wireless switching control unit 19 upstream message storage unit 20 upstream transmission unit 21 downstream message storage unit 22 downstream transmission unit 23 line control means 24 Radio message reception analysis means 25 Communication control means

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Satoshi Morita 1006 Kadoma, Kadoma, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd.

Claims (3)

[Claims] 1. A line control means which is called from a central monitoring device via a public line and which connects a plurality of data terminal devices to the public line through wireless communication via wireless communication according to an instruction of a message from the central monitoring device. In the line terminal device for controlling one of the data terminal devices selected by the activation request message of the central monitoring device to communicate with the central monitoring device via the wireless communication,
Only when the through wireless communication is connected, a wireless telegram reception analysis unit that intercepts and analyzes a telegram between the central monitoring apparatus and the selected data terminal apparatus, and the central monitoring apparatus corresponding to the intercepted and analyzed telegram. And a communication control unit for controlling communication between the selected data terminal device and the wireless telegram reception analysis unit intercepts the telegram which is a communication end telegram from the central monitoring device to the data terminal device. ,
The communication control means switches the public line from a through wireless communication connection to a connection to the line control means so that the line control means can receive a telegram following a communication end sentence of the central monitoring device. Line terminal device. 2. An upstream message storage unit for constantly updating and storing the upstream message from the data terminal device to the central monitoring device, which is intercepted by the wireless message receiving / analyzing unit during the through wireless communication connection, and the upstream transmission for transmitting the stored upstream message. And a radio message reception / analysis means intercepts a telegram that is a retransmission request telegram from the central monitoring device to the data terminal device, the communication control means, unless there is an abnormality in the stored telegraphic message, the central monitoring device. The line terminal device according to claim 1, wherein transmission control is performed to the line terminal device. 3. A downlink message storage unit for constantly updating and storing a downlink message from a central monitoring device to a data terminal device intercepted by a radio message receiving / analyzing means during through wireless communication connection, and a downlink transmission for transmitting the stored downlink message. When the message received by the wireless message reception analysis means is a retransmission request message from the data terminal device to the central monitoring device, the communication control means uses the data terminal as long as there is no abnormality in the stored downlink message. The line terminal device according to claim 1, wherein transmission control is performed to the device.