JPH0951586A - Data transmission equipment - Google Patents

Abstract

(57) [Abstract] [Purpose] The middle of the transmission path is made wireless without adversely affecting the existing system. Shorten the time of wireless communication,
Reduce communication errors and ensure corrective action when an error occurs. Reduce the memory capacity when converting the communication speed. Allow terminals to communicate in a real-time sense. [Configuration] The terminal 2 receives a telegram with a slow communication speed B ₀ from the device 1, and every time a certain number of characters are received, STX, ETX, and BCC are attached to the data to form one block, which is high-speed. Wireless transmission is performed to the terminal 3 at the communication speed B ₁ . When receiving this, the terminal 3 issues a resend request if there is an error. If there is no error, the data sandwiched between STX and ETX is returned to the original communication speed B ₀ and continuously transmitted to the device 4 in the order of the blocks sent.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data transmission apparatus suitable for making part of a transmission line wireless such as an automatic meter reading system for measuring instruments such as water meters and gas meters.

[0002]

2. Description of the Related Art In an automatic meter reading system or the like, a part of a transmission line of an existing system may be made wireless, and a part to be made wireless is between a meter and a T-NCU or between a meter and a terminal transmitter. Is.

Since wireless communication is more susceptible to the adverse effects of disturbances such as temporary obstacles such as passage of cars and people than the case of wired communication, communication quality can be stabilized by converting the communication speed to allow high speed communication. To do.

FIG. 8 shows a communication procedure according to this type of conventional technique. This figure shows the communication procedure between the meter reading center (center side) and the meter (meter side) in the automatic meter reading system. It is between the center side 1 and the first converter 2 and the second converter 3 And the meter side 4 are wired, and the first converter 2 and the second converter 3 are wireless.

In a wired transmission line, the communication speed is B ₀ bps,
Assuming that the communication speed is B ₁ bps on the wireless transmission path, when transmitting a message with a bit length of n from the center side 1 to the meter side 4, the message from the center side 1 to the first converter 2 is transmitted. It takes n / B ₀ seconds for transmission. Then, it takes n / B ₁ second to convert the communication speed to B ₁ by the _first converter 2 and wirelessly transmit the message to the second converter 3. Further, it takes n / B ₀ seconds to restore the data communication speed of the second converter 3 to the original speed B ₀ bps and transmit it to the meter side 4.

In this way, from the center side 1 to the meter side 4
To send a message to (n / B₀) + (N / B₁) + (N / B₀) It takes [seconds] and the transmission of the message ends when the communication speed is not converted.
Time required to do n / B ₀Compared to seconds, (n / B₁) +
(N / B₀) Extra time is spent [seconds]. This
The extra time is shown by * 1 in Figure 8.

Normally, a response message is returned from the meter side 4 in response to the received message. The bit length of this response message is n ₁
Then, also in this case, (n ₁ / B ₁ ) × (n ₁ /
B ₀ ) [second] takes extra time as compared with the case where the communication speed is not converted. This extra time is indicated by * 2 in Fig. 8.

Therefore, if the communication speed is converted on the wireless transmission line, the time from the end of sending the 1st telegram message to the start of receiving the response telegram (n + n ₁ ) · [(1 / B ₁ ) + ( 1 / B ₀ )] [seconds]
= T ₁ [seconds] extra time is required, and if this time T ₁ exceeds the timeout time T ₀ seconds, a communication error occurs.

For example, in 8-bit communication, 300 bps → 1
When a speed conversion of 200 bps is performed, assuming that n = 10 bits × 40 characters, n ₁ = 10 bits × 300 characters, and timeout time T ₀ = 10 seconds, T ₁ = (400 + 3000) [(1/1200) + ( 1
/300)]=14.17 seconds, and T ₁ exceeds the timeout time T ₀ = 10 seconds, and a communication error occurs.

[0010]

SUMMARY OF THE INVENTION In the above conventional technique,
A time delay T ₁ occurs in proportion to the length of a telegram for converting the communication speed, and in the worst case, when the reception of the telegram after the conversion ends, the timeout time T ₀ is exceeded and a communication error occurs.

Therefore, in order to avoid the occurrence of such a communication error, it is necessary to limit the length of a telegram or to perform dummy communication to extend the time-out period, which greatly affects the operation system. There was a problem. Further, in the above-mentioned conventional technique, error processing cannot be performed until the entire electronic message is received. Therefore, if a communication error occurs due to a disturbance on the wireless transmission path, it takes a long time to complete the correction process, and there is a problem that the timeout time may be exceeded.

Furthermore, when converting the communication speed,
Since the entire message is stored in memory and converted in order,
There was also a problem that a large amount of memory was required. Further, since the entire telegram is continuously transmitted, there is a problem that the life of the battery is shortened if a battery power source is used in the wireless transmission line portion.

Therefore, an object of the present invention is to provide a data transmission device which can solve these problems.

[0014]

In order to achieve the above-mentioned object, the invention of claim 1 comprises a first device (1) for outputting transmission data by a character code, and the first device (1). Each time a fixed number of characters are received, one block consisting of each character code indicating the start and end of data transmission, transmission data and error control code,
The first terminal (2) that converts the communication speed to high speed and wirelessly transmits the block, and the block signal wirelessly transmitted from the first terminal (2) are received, and the received signal has no error. In the case, the transmission data sandwiched between the start character code and the end character code is the original communication speed (B ₀ bps).
The second terminal (3) for returning the transmission data to the second device (4) while continuing the transmission data in the order of the blocks transmitted.
The data transmission apparatus is characterized in that the transmission timing is set to a timing after transmission of at least one retransmittable time (T2) after receiving a telegram of the corresponding block before returning the communication speed. .

According to a second aspect of the present invention, a meter (1A) and a first wireless device (2A), which are connected to each other through a wired transmission line (5) and perform data transmission between them at a low communication speed,
A second wireless device (3A) which is connected to the first wireless device (2A) by a wireless transmission path and performs data transmission between the wireless devices at a high communication speed; and the second wireless device. (3A) and a T-NCU (4A) that is connected by a wire transmission path (6) and performs data transmission between them at a slow communication speed, and includes a first wireless device (2A) or a second wireless device (2A). When the communication speed is increased by the wireless device (3A), each time a fixed number of characters are received, this is converted into one block and transmitted, and each block is a character code indicating the start and end of the block. And a transmission data and an error control code, the first radio (2A) or the second radio (3A)
When returning to the original slow communication speed with, if there is no error in the received block, the transmission data sandwiched between the start code (STX) and the end code (ETX) is returned to the original communication speed and sent. In the automatic meter-reading system, the data is continuously transmitted in the order of the received blocks, and the transmission timing is at least after a lapse of at least one retransmittable time after receiving the telegram of the corresponding block before the speed conversion. It is a data transmission device.

According to a third aspect of the present invention, in the data transmission device according to the second aspect of the automatic meter reading system,
The wireless device (2A) and the second wireless device (3A) perform transmission at a high wireless communication speed every time one block of a telegram having a low communication speed is received, and unless the retransmission request is issued, It is characterized in that a pause period is provided in which no radio wave is emitted until one block is received.

[0017]

First, the invention of claim 1 will be described with reference to FIG.
A description will be given based on (b) and (c). The first device 1 outputs the data before speed conversion to the first terminal 2 at the communication speed B ₀ bps.

Each time the first terminal 2 receives a certain number of characters of the data from the first device 1, a character code (start code) indicating the start of data transmission and a character code indicating the end (end). Code), one block shown in FIG. 1 (c) consisting of the transmission data of a certain number of characters and the error control code, and converting the communication speed to a communication speed B ₁ bps higher than the communication speed B ₀ bps. , The block is wirelessly transmitted to the second terminal 3.

In FIG. 1B, the transmission data before speed conversion output from the first device 1 to the first terminal 2 is No1 having the constant number of characters starting from the beginning of the data, and the constant number of characters following it. No. 2 and ... No. 4, N in order
Although shown as o5, ..., In this way, the first device 1
The data transmission from the first terminal 2 to the first terminal 2 is performed by continuously transmitting a certain number of characters as one transmission data.

Each time the first terminal 2 receives the above-mentioned fixed number of characters from the first device 1, the first terminal 2 forms one block consisting of a start code, a fixed number of characters of data, an end code and an error control code. Higher communication speed B ₁
It is converted to bps and wirelessly transmitted to the second terminal 3.

In FIG. 1 (b), data before speed conversion transmitted from the first device 1 to the first terminal 2 is data No1, No2, No3, No4 for each of the fixed number of characters.
No. 5, ... Is shown as one piece of transmission data concatenated, and transmission data No. 1 ...
As a block in which a start code, an end code and an error control code are added as shown in FIG. 1C, a block for wireless transmission from the first terminal 2 to the second terminal 3 at a high communication speed B ₁ bps is also included. No. 1, No. 2, ... As shown in FIG.
The drawing is simplified by showing.

The second terminal 3 receives this wirelessly transmitted block signal, and if there is no error in the received signal, it uses a start character code (also called start code) and an end character code (also called end code). The sandwiched transmission data is returned to the original communication speed B ₀ bps, and the transmission data is continuously transmitted to the second device 4 in the order of the blocks transmitted. FIG. 1B also shows data that is reconverted to the original communication speed and transmitted to the second device 4.

The second terminal 3 receives the block signal transmitted by radio, and when the received signal has an error,
The first terminal 2 makes a retransmission request to the first terminal 2, and the first terminal 2 responds to the retransmission request by sending the block signal containing the error to the second terminal 2.
It is retransmitted to the terminal 3.

FIG. 1 (b) illustrates a retransmission request and a retransmission procedure for the block signal No3. In consideration of the occurrence of such a retransmission request, the transmission timing is a time T ₂ at which at least one retransmission is possible after the message is received before the communication speed is returned to the original speed B ₀ bps. After that (FIG. 1B).

Next, the operation of the invention of claim 2 will be described. When data is transmitted from the meter-reading center to the meter (1A) side, data is transmitted from the T-NCU (4A) to the second wireless device (3A) by wire at a low communication speed.

When the second wireless device (3A) receives the transmission data, each time a predetermined number of characters are received, the second wireless device (3A) performs speed conversion by converting the data into one block, and at the same time, each block is constant. Start character code (STX) (also referred to as start code) before the data of the number of characters and end character code (ET
X) (also called end code) and error control code (BC
C) is added and configured. The first wireless device (2A) receives the block signal wirelessly transmitted from the second wireless device (3A), and if there is no error in the received block, the start code (STX) and the end code (ETX). ) Is returned to the original slow communication speed, the data is sent in the order of the blocks sent continuously to the meter (1A) by wire, and the transmission timing is the message of the corresponding block before speed conversion. It is assumed that at least one retransmitted time has elapsed after the reception.

From the meter (1A) side, the first wireless device (2
A), when data is transmitted to the meter-reading center side via the second wireless device (3A) and T-NCU (4A), the content of the data is different from the case of communication from the center side to the meter (1A) side. While different, the transmission directions are naturally opposite.

In this case, the meter (1A) transmits the transmission data by wire at a low communication speed to the first wireless device (2A). Each time the first wireless device (2A) receives a fixed number of characters of this data, it performs speed conversion at high speed using this as one block, and a start code (STX) is added before and after the fixed number of characters of data. Each block is constructed by adding an end code (ETX) and an error control code (BCC).

The second wireless device (3A) receives this block signal, and each time it receives one block signal, if there is no error in the received block signal, the start code (ST
X) and the end code (ETX) are returned to the original slow communication speed, the data is continuously transmitted in the order of the blocks that were sent, and the transmission timing is the message of the corresponding block before the speed conversion. It is assumed that at least one retransmitted time has elapsed after the reception.

According to a third aspect of the present invention, in the data transmission apparatus according to the second aspect, each of the wireless devices (2A) and (3A) wirelessly performs fast transmission every time one block of a certain number of characters receives a telegram having a slow communication speed. In addition to performing transmission at the communication speed, a pause period is provided in which radio waves are not emitted until the next one block is received unless there is a retransmission request from the radio device (3A or 2A) on the partner side.

[0031]

[First Embodiment] FIGS. 1A and 1B corresponding to claim 1.
According to the data transmission device shown in (c), the first aspect of the present invention
An embodiment will be described.

The telegram before the speed conversion is transmitted from the first device 1 to the first terminal 2 by wire at the communication speed B ₀ bps. First
When the terminal 2 receives a fixed number of n characters of a message sent from the first device 1 at a communication speed of B ₀ bps,
This is set as one block and is wirelessly transmitted to the second terminal 3 at high speed B ₁ bps.

In each block, a code indicating the beginning of the block, such as STX and SOH, is the head, and then n character data is transmitted as received. Then E
Add a code that indicates the end of the block, such as TX or ETB,
Finally, an error control code such as BCC is sent to complete the transmission of one block (FIG. 1 (c)).

The second terminal 3 receives the first transmission block No1.
Is received, after at least one retransmission request and a time T ₂ sufficient to receive a response to this request have elapsed,
The transmission of the transmission data to the second device 4 is started at the original slow communication speed B ₀ bps.

The second terminal 3 is transmitting the transmission block No1 to the second device 4 and the next transmission block No2 is the first transmission block No2.
Since it is sent from the terminal 2, the terminal 2 receives this, and if there is an error in the data, a resend request is made.

Since the second terminal 3 has completed the reception of the transmission block No2 by the time the transmission of the transmission block No1 is completed, when the No1 data transmission to the second device 4 is completed, the second terminal 3 continues. No. 2 data can be transmitted and the data transmitted from the second terminal 3 to the second device 4 is not interrupted.

The time delay due to the speed conversion is the transmission time for a maximum of two blocks. For example, at B ₀ = 300 bps, 1
When the block consists of 10 characters, the time delay is 33.3 ms × 10 × 2 = 666 ms, but the timeout time is usually 10 seconds or more, so there is no fear of adversely affecting the operation of the system or equipment. .

This time delay also reduces the number of characters n in the transmission block, and the second terminal 3 to the second device 4
It is possible to further shorten the transmission timing by transmitting the re-converted data to be transmitted to the terminal.

[0039]

Second Embodiment A second embodiment shown in FIG. 2 is an application of the present invention to an automatic meter reading system for a meter (measuring instrument) such as a water meter or a gas meter, and corresponds to claims 2 and 3.

Reference numeral 1A is a meter, which is connected to the first wireless device 2A by a wired transmission line 5 and has a communication speed of 300b.
It is defined in ps. A second wireless device 3A is connected to the first wireless device 2A via a wireless transmission path, and the communication speed between the two is set to 1200 bps, which is four times the 300 bps.

Reference numeral 4A is a T-NCU (terminal network control unit), which is connected to the second wireless device 3A by a wired transmission line 6, and the communication speed between the two is 300, which is the same as the communication speed of the transmission line 5.
It is set to bps.

Reference numeral 7 is a center device located at the meter reading center of the automatic meter reading system, which is connected to the T-NCU 4A via a telephone line, and the communication speed between the two is the same as the communication speeds of the transmission lines 5 and 6. It is set to 300 bps.

Communication between the center device 7 and the meter 1A is bidirectional. Next, the conversion of the communication speed, the wireless transmission, the communication timing, the error correction processing and the like in the embodiment of FIG. 2 will be described in detail.

(1) From the communication speed of 300 bps to 120
To convert to 0 bps, the received 300 bps telegram is 1
This is done with a telegram having the configuration shown in FIG. One character has a 10-bit structure.

Therefore, the 1200 bps telegram is divided into a plurality of transmission blocks from transmission block No1 to transmission block Noi, and each transmission block is 300 bps.
Each time 10 characters are received from the beginning of the message, a start code STX is added to the beginning of the message, the 10-character data is added to the start code, and then an end code ETB and an error control code BCC are added to one transmission block. And

Therefore, a transmission block for a 1200 bps message is provided.
No. 1 is the first 10 keys of the 300 bps message.
Character, ie STX, d₁, D₂, D_Three, ..., d₉of
Telegram with STX, ETB and BCC attached to the front and back respectively
It becomes the form. Note that d₁, D ₂, D_Three, ..., d₉Is day
It is In addition, calculation of error control of transmission block No1
The target is the STX shown in the transmission block No. 1 of FIG.
d₁, D₂, ..., d₉Transmission data and ETB.

Similarly, transmission blocks No2, ..., Transmission block Noi of 1200 bps telegram are created in sequence, but the final transmission data in the transmission block i is 10
If the number of characters is less than the number of characters, dummy data is inserted after BCC ', which is an error control code in a telegram of 300 bps, to make 10 characters as shown in the lower right part of FIG.

(2) Wireless communication speed 1200 bps
Is transmitted every time 10 characters (1 block) of a 300 bps telegram are received, and there is a pause period during which no radio wave is emitted until the next 10 characters are received unless there is a retransmission request.

By so doing, the battery life can be extended when a battery is used as the power source of the radio device. Since the battery is not used continuously for a long period of time but intermittently for a short period of time, the battery life is extended.

FIG. 4 shows the timing of transmission by radio waves and pause.
Shown in (3) The wireless device that has received the message of the transmission block No. 1 having the communication speed of 1200 bps is 75 after the reception of the block is completed.
The mark signal is sent to the wired transmission line (communication line) of 300 bps within ms, and after 150 to 225 ms, the data of the transmission block No. 1 is sequentially transmitted at the communication speed of 300 bps (FIG. 5).

The first character of the No. 1 data is ST
However, the transmission timing of this STX is 1200b.
It is the timing to start receiving the No. 2 message in ps.
This relationship is shown in FIG.

Communication speed from 300 bp to 1200 bp
Since it is converted to s in units of 10 characters, 30
A 0 bps data block requires 33.3 ms x 10 characters = 333 ms to be transmitted. This time is indicated by t ₁ in FIG.

Also, this data block is set to 1200 bp
"STX" + data (10 characters) + "ETB" + to transmit by s
13 characters of “BCC” are required, and the required time is 8.325 ms × 13 characters = 108.225 ms, which is t ₂ in FIG.

[0054] Since the mark time 300bps is required 150~250ms pursuant relating to message format automatic meter reading, if determined the time t ₀ shown in FIG. 5 in the range of 0 ≦ t ₀ ≦ 75 m _s, the mark time t _M In FIG. 5, since t _M = t ₁ −t ₂ −t ₀ t ₁ −t ₂ = 225 ms, 150 ms ≦ t _M ≦ 225 ms, which satisfies the necessary condition.

(4) After the end of the mark, data is successively transmitted in sequence of d ₁ , d ₂ , ..., dn, following “STX”. Then, a space is sent after "ETX" and "BCC '" to end the transmission of 300 bps.

(5) In wireless communication with a communication speed of 1200 bps, if an error occurs in the data, a retransmission request is made from the receiving side wireless device to perform error correction processing. Note that this process ends before the next transmission block is sent, so
The 300 bps telegram that is reconverted to the original slow communication speed and transmitted is not interrupted.

In the embodiment of the present invention, after the first wireless device 2A starts receiving the telegram from the data 1A, the second wireless device 3
There is a time delay of 2 blocks, that is, 333 ms × 2 = 666 ms, before A starts transmitting a telegram to T-NCU4A at 300 bps, so that the center apparatus 7 also has a 666 m delay.
It can be received only with a delay of s.

Further, the center device 7 which has received the electronic message from the meter 1A returns a response electronic message to the meter 1A, but in this case as well, a time delay of 666 ms occurs similarly to the above, and therefore the meter 1A side transmits the message. Then, the response message is received with a delay of 666 × 2 = 1.332 s.

The time-out time of the meter 1A is usually 10
Since it is about a second, in the system of this embodiment, the meter and the T-N
Compared to the case where the CU is directly connected, the timeout time is reduced by 1.332 seconds, which is effectively 8.668 seconds.
It does not adversely affect the entire system.

Since the delay of 1.332 seconds is constant regardless of the length of the message to be transmitted, it is not necessary to limit the data to be transmitted. In order to shorten this delay time,
The timing of reconverting the communication speed from 1200 bps to 300 bps and returning it is one block earlier, that is, 1200 bp
300 bp at the same time when No. 1 data is received in s
If the method of transmitting at s is used, the time is half, 666 ms.

However, in this case, if an error occurs during data reception of 1200 bps, 300 bps at that time.
Therefore, the transmission is canceled and communication stability is lost.

In particular, since wireless communication is apt to cause an error due to the influence of disturbance, in the above-mentioned method, 300 bps communication may be interrupted midway. However, in the present embodiment, it takes time to perform the retransmission procedure for each block, and since it ends before the next transmission block is sent, the reconverted message may be cut off in the middle. Without, stable data transmission is possible.

The timing for performing this retransmission procedure will be described in more detail with reference to FIG. Data transmission time t
_D is 1200b for 1 character (10 bits)
It is 8.325 ms in ps and the number of characters is "STX" + data (10) + "ETB" + "BC".
Since there are 13 characters in “C”, t _D = 8.325 ms × 13 characters = 108.22
5 ms.

The transmission time t _R of the retransmission request message is t _R = 8.325 ms × 4 = 33.3 ms when the structure of the retransmission request message is 4 characters of “STX” +1 character + “ETX” + “BCC”. Becomes

Therefore, the time Td required for one retransmission is Td = 2 × t _D + t _R + t ₁ + t ₂ = 2 × 108.225 ms + 33.3 ms + t ₁ + t ₂ = 249.75 ms + t ₁ + t ₂ .

Since both t ₁ and t ₂ are switching times from reception to transmission, if these are set to 10 ms, respectively, Td≈270 ms <333 ms, and the process ends before the transmission of the next block.

Further, if the timing for re-converting the communication speed to 300 bps is adjusted to the Td as shown in FIG. 7, the total delay time becomes 333 ms + 270 ms = 603 ms. The delay time is 206 seconds, which is 0.126 seconds shorter than the case where two blocks are delayed as described above.

The delay time Td is 1 when the speed conversion is performed.
It can also be shortened by reducing the number of characters per block. For example, if the transmission data of one block is reduced to 7 characters, the number of characters of the telegram of one block is “STX” + data (7) + “ETB” + “BCC”, which is 10 characters, so t _D = 8 .325 ms × 10 = 83.25 ms Td = (2 × 83.25 + 33.3 + 10 + 10) ms
= 219.8 ms.

Since the transmission time of one block at the communication speed of 300 bps is 33.3 ms × 7 = 233.1 ms, the total delay time is 233.1 ms + 219.8 ms = 452.9 ms.

Therefore, in a single communication, 905.
Since the delay time is 8 ms, the influence on the timeout time can be suppressed to 1 second or less. As mentioned above, even if it takes time to perform the retransmission procedure for each block, the delay time due to speed conversion does not have a bad influence on the operation of the system, and the terminals of the system can operate in a near real-time sense. Also, since it is possible to reliably deal with the occurrence of an error during communication, stable communication can be performed.

As for the number of transmission characters per block and the transmission timing, an optimum value may be selected in consideration of the time-out time of the operating system, and the optimum value can be easily set as described above. Can be set.

[0072]

According to the first aspect of the present invention, the delay time of the transmission timing generated during the speed conversion is constant irrespective of the length of the message, and this delay time is sufficiently shorter than the system time-out time. Therefore, the system is not adversely affected.

Further, since it is possible to request retransmission for each block, it is possible to cope with an error occurrence during speed conversion. Since the transmission timing is delayed by the time required for retransmission, the reconverted message will not be interrupted even if the retransmission process is performed.

Therefore, a part of the transmission path can be made wireless and high-speed communication can be performed without changing the existing system. Therefore, the first device (1) and the second device (4) or the meter (1A) can be connected. ) And the center devices (7) and the like need not be aware of speed conversion, and have an advantage that they can communicate in a real-time sense. Further, the influence of disturbance on the wireless part can be reduced, the occurrence of errors can be reduced, and the error correction can be surely dealt with.

Further, since the speed is not converted in sequence after storing the entire electronic message, but is sequentially converted in block units, the required memory is 2 blocks (1 block is 10 blocks).
(20 bytes for a character) is sufficient, and there is an advantage that a memory having a smaller capacity than the conventional one can be used.

According to the invention of claim 2, in the automatic meter reading system of the meter, the same effect as in the case of claim 1 can be obtained. Further, in the invention of claim 3, in the invention of claim 2, the first
And the emission of radio waves from the second wireless device is intermittent, so when a battery is used as a power source, it is used intermittently for a short period of time.
There is an advantage that the battery life can be extended.

[Brief description of drawings]

FIG. 1 is a block diagram of a first embodiment of the present invention, FIG.
(B) is a figure explaining a transmission timing, (c) is a figure explaining the message format of a transmission block.

FIG. 2 is a block diagram of a second embodiment of the present invention.

FIG. 3 is a diagram illustrating a message format of the second embodiment of FIG.

FIG. 4 is a diagram showing a part of the transmission timing of the second embodiment of FIG.

5 is a diagram showing the transmission timing of the second embodiment of FIG.

FIG. 6 is a diagram for explaining the transmission timing at the time of a retransmission request between both wireless devices of the second embodiment of FIG.

FIG. 7 is a diagram illustrating a delay time of transmission timing in the second embodiment of FIG.

FIG. 8 is a diagram illustrating a communication procedure and a transmission timing of a conventional technique.

[Explanation of symbols]

1 1st apparatus 1A meter 2 1st terminal 2A 1st wireless machine 3 2nd terminal 3A 2nd wireless machine 4 2nd apparatus 5 and 6 Wired transmission line 7 Center apparatus B ₀ , B ₁ communication Speed STX Start code ETX End code BCC Error control code T ₂ hours

Claims (3)

[Claims] 1. A first device (1) for outputting transmission data according to a character code, and each indicating a start and an end of data transmission each time a constant number of characters is received from the first device (1). A first terminal (2) for converting one block consisting of a character code, transmission data, and an error control code, and converting the communication speed to high speed to transmit the block wirelessly, and wireless communication from the first terminal (2). When the transmitted block signal is received and if the received signal has no error, the transmission data sandwiched between the start character code and the end character code is returned to the original communication speed (B ₀ bps) and is transmitted. A second terminal (3) for continuously transmitting the transmission data to the second device (4) in the order of blocks, and the timing of the transmission is small after receiving the telegram of the corresponding block before returning the communication speed. The time (T
A data transmission device characterized in that after 2) has elapsed. 2. A meter (1A) and a first wireless device (2A), which are connected to each other by a wired transmission path (5) and perform data transmission between them at a low communication speed, and the first wireless device. Second wireless device (3A) connected to the wireless device (2A) by a wireless transmission path and transmitting data between the wireless devices at a high communication speed, and a wire connected to the second wireless device (3A) TN which is connected by the transmission line (6) of the above and performs data transmission between them at a low communication speed.
CU (4A) is provided, and when the communication speed is increased by the first wireless device (2A) or the second wireless device (3A), this is treated as one block each time a fixed number of characters are received. Each block is composed of a character code indicating the start and end of the block, transmission data, and an error control code while being converted in speed, and transmitted by the first wireless device (2A) or the second wireless device (3A). When returning to the original slow communication speed, if there is no error in the received block, start code (STX) and end code (ET
The transmission data sandwiched between X) is returned to the original communication speed, and the data is continuously transmitted in the order of the transmitted blocks. The transmission timing is at least once after receiving the telegram of the corresponding block before the speed conversion. A data transmission device in an automatic meter-reading system, characterized in that the time after which re-transmission is possible has elapsed. 3. The first wireless device (2A) and the second wireless device (3A) perform wireless transmission at a high communication speed every time one block of a telegram having a low communication speed is received, and request retransmission. The data transmission device according to claim 2, wherein a pause period is provided in which no radio wave is emitted until the next one block is received unless there is such a case.