JP7788411B2 - Telemeter and communication method using the same - Google Patents

Description

The present invention relates to a telemeter using a public line and a communication method using the same, and in particular to a telemeter configuration that can reliably transmit status signal data acquired at the telemeter installation location, such as a pumping station, to a higher-level monitoring device, and a communication method in the event of an abnormality.

Traditionally, monitoring and control systems have been known in which data from monitored objects is imported into a communications terminal installed on-site, and the status of the monitored object is either transmitted to a remote location via communications and displayed, or commands are sent to on-site equipment to remotely control it. For example, telemeters are widely used in remote water supply and sewerage systems, water distribution facilities, and industrial production facilities. When using telemeters, public lines such as analog dedicated lines have been widely used as communication lines. Currently, the use of always-on lines via networks such as broadband lines is increasing, but broadband lines tend to be expensive, and service is often not provided in high-cost installation locations (such as airports) due to reasons such as the difficulty of installing communication lines in mountainous areas. Therefore, there is still strong demand for public lines.

The technology of Patent Document 1 is known as an example of a monitoring system that uses such a telemeter. Patent Document 1 discloses a telemeter that uses a dedicated line and that, when the calculation unit within the telemeter hangs up, is provided with a switching unit (switching logic) that switches to a message generated by a standby calculation unit, and is equipped with a modem that transmits messages from the calculation unit or standby calculation unit over the dedicated line, thereby allowing communication to continue even when the telemeter hangs up.

Japanese Patent Application Laid-Open No. 2020-154443

In the telemeter described in Patent Document 1, if the calculation unit hangs up, control continues by including fixed values appropriate for operating the equipment in the message generated by the backup calculation unit. However, because the message generated by the backup calculation unit does not contain normal values at the actual pump station, there is a problem in that normal operation cannot be continued.

The present invention has been made in view of the above background, and its object is to provide a telemeter and a communication method using the same that can reliably transmit a fault signal at the telemeter installation location to a higher-level monitoring device even if the processor of the telemeter communication device hangs up.
Another object of the present invention is to provide a telemeter and a communication method using the same in which a switching unit is provided in the telemeter for switching the transmission path and transmission content when the processor hangs up, thereby enabling normal monitoring functions to continue.

Representative features of the invention disclosed in this application are as follows.
According to one aspect of the present invention, the present invention is applied to a telemeter having a telemeter communication device connected to a public line and a programmable logic controller (PLC) that receives a fault signal from a monitored object and transmits it to the telemeter communication device. The PLC has a function of outputting a data string indicating a fault condition to the telemeter communication device upon receiving the fault signal. The telemeter communication device has a processor that receives the data string from the PLC and generates normal-state transmission data to transmit to a host monitoring device, a modem that communicates with the host monitoring device via the public line, and a switching unit. The switching unit outputs the data string from the PLC to either the processor or the modem. A bypass line is also provided to connect the PLC and the modem when the processor is not operating normally. The switching unit is configured with a selector switch that connects the PLC and the processor when the processor is operating normally and connects the PLC and the bypass line when the processor is not operating normally. The processor and the PLC are connected via an RS-232C communication line, and the modem and the PLC are connected via an RS-232C communication line.

According to another feature of the present invention, the changeover switch includes a first relay with an a-contact that connects the PLC output to the processor's input line, and a second relay with a b-contact that connects the PLC output to the bypass line. These first and second relays are controlled by a timer relay. The timer relay outputs a control signal when the processor is operating normally and stops outputting the control signal a predetermined time after the processor's operation becomes abnormal. The processor creates normal transmission data by adding additional information, including the identification information of the monitored object and date and time information, to the data string received from the PLC.

According to yet another feature of the present invention, when the telemeter modem receives a data string via the bypass line, it connects to a preset destination and automatically transmits the data string. The data string generated by the PLC may be configured to include identification data indicating a "failure" in the telemeter communication device, and when the processor successfully receives the data string from the PLC, the identification data in the data string may be changed from "failure" to "no failure." The public line modem has two input ports, and when a signal is received at the input port via the bypass line, it establishes a communication path via the public line to the destination according to a preset procedure and automatically transmits the received normal transmission data or the data string from the PLC to the higher-level monitoring device.

According to the present invention, the modem connected to the public line and the PLC that receives the pump station status signal can be connected via a bypass line via a switching unit. Therefore, even if the processor in the telemeter communication device hangs up, the PLC output can be switched to be sent to the modem, and a fault signal from the remotely monitored object can be reliably sent to the host monitoring device as transmission data in the event of a fault. Furthermore, the host monitoring device that receives the transmission data can easily determine whether the processor in the telemeter has stopped or is operating normally based on the length and content of the transmission data, allowing the host monitoring device to perform highly accurate monitoring tasks.

1 is a block diagram showing a configuration of a telemeter 1 according to an embodiment of the present invention. 2A and 2B are partial block diagrams showing the internal configuration of the telemeter communication device 2 of FIG. 1, in which (A) shows the connection state of the switching circuit 5 when the CPU 3 is operating normally, and (B) shows the connection state of the switching circuit 5 when the CPU 3 is stopped and not operating normally. 1A and 1B are diagrams showing the transmission status of transmission data in an embodiment of the present invention, in which (A) shows the flow of transmission data when CPU 3 is operating normally, and (B) shows the flow of transmission data when CPU 3 is stopped. 4A and 4B are diagrams showing the contents of the transmission data in FIG. 3, in which (A) is transmission data 50 generated by the PLC 9, and (B) is transmission data 60 processed by the CPU 3. FIG. FIG. 10 is a diagram showing the data structure of transmission data 50A and 60A according to a first modified example of the present invention. 10A and 10B are diagrams showing the data structure of transmission data 50B and 60A according to a second modified example of the present invention.

The present invention will now be described in detail with reference to specific embodiments. First, a telemeter 1 according to a first embodiment of the present invention will be described using Figure 1. The telemeter 1 is a device provided for monitoring the status of target equipment by a host monitoring device 100, and is primarily composed of a PLC 9 (Programmable Logic Controller) and a telemeter communication device 2 that collects signals transmitted from the PLC 9 and transmits them to the external host monitoring device 100. The telemeter 1 receives an output, i.e., a fault signal 21, emitted when a fault occurs in a remotely monitored object, in this case a pump 40 at a pumping station, etc., via the PLC 9, converts the output into a predetermined data sequence 22, transmits it to the CPU 3, and after processing the data by the CPU 3, transmits it as transmission data 25 to the host monitoring device 100 via the public line 101 via the modem 4.

In recent years, real-time monitoring using broadband lines has become commonplace for data acquisition from remotely monitored objects to the host monitoring device 100. Meanwhile, monitoring using telemeters 1 using public lines has also become commonplace, either in addition to or instead of real-time monitoring using broadband lines. Telemeters 1 often employ a timely transmission method (sending data only when an abnormality occurs), transmitting a signal to the host monitoring device 100 when a fault occurs in the remotely monitored object. Therefore, if a failure occurs in the CPU 3 constituting the telemeter 1, the telemeter 1's communication function may cease, potentially preventing it from sending a signal indicating an abnormality to the host monitoring device 100. Furthermore, when an abnormality occurs, the host monitoring device 100 may be unable to determine whether the telemeter 1 is malfunctioning or the remotely monitored object (pump 40) is malfunctioning. Therefore, in this embodiment, a signal indicating an abnormality can be reliably transmitted to the host monitoring device 100 even when the CPU 3 of the telemeter 1 stops due to a hang-up or other reason. In the telemeter 1 of this embodiment, rather than fixing the output of the PLC 9 via input lines 11 and 12 and inputting it to the CPU 3, the telemeter 1 is provided with a switching circuit (switching unit) 5 and a bypass line 15 so that the output from the PLC 9 can be transmitted directly to the modem 4, bypassing the CPU 3.

PLC 9 is a control device (controller) used to control and monitor equipment and facilities, and uses a microprocessor to run software. Here, it monitors the operation of a pump 40 installed at a pumping station. When a fault signal 21 indicating a fault is detected, it generates a data sequence 22 indicating the fault and transmits it to the telemetry communication device 2 via the RS232C line 11. Data sequence 22 is a short signal, e.g., a few bits to a few bytes, that defines a bit sequence corresponding to the status of each part of the pump. Each bit is assigned a flag indicating an abnormality (e.g., bit "1") or a normal flag indicating a normal condition (e.g., bit "0"). Data sequence 22 thus has a content such as "001000..."; the host monitoring device 100 can determine the detailed status of the pump 40 depending on which bit contains a "1" indicating an abnormality. Note that how each bit of the data sequence 22 output by the PLC 9 is defined and how many bits of the data sequence are set are arbitrary, and can be set as a program in the PLC 9 according to the number of objects to be monitored. Also, if there are multiple pumps 40, such as 40-1, 40-2, etc., a data sequence 22 with a data capacity corresponding to each pump 40-1, 40-2, etc. can be set.

The CPU (Central Processing Unit) 3 is a processor that executes a program to generate the message to be transmitted, i.e., normal transmission data 24, from the received data sequence 22 and transmits it to the modem 4. Any type of processor may be used, including not only a CPU but also other processors, such as an MPU (Micro-Processing Unit). The modem 4 is a well-known communication device for bidirectional communication with the upper-level monitoring device 100 using a public line 101 such as a telephone line. The modem 4 used in this embodiment has a first input port 4a for inputting the normal transmission data 24 from the CPU 3 and a second input port 4b for inputting the data sequence 23 from the bypass line 15. Upon receiving the normal transmission data 24 from the first input port 4a, the modem 4 establishes a connection with a predetermined destination (here, the upper-level monitoring device 100) in accordance with instructions from the CPU 3 or a predetermined procedure, and transmits the abnormal transmission data 23 as transmission data 25. Furthermore, when the modem 4 receives the data sequence 23 from the second input port 4b, it establishes a connection with the designated destination (here, the host supervisory device 100) according to a preset procedure and automatically transmits the data sequence 23 as transmission data 25. To enable this connection, the modem 4 stores information such as the telephone number (or IP address, etc. used to specify the destination) of the host supervisory device 100 (not shown), the communication method, and the communication speed. The modem 4 is equipped with a retry function, which attempts to connect multiple times if the destination (the host supervisory device 100) is busy. Note that the number of destinations set in the modem 4 is not limited to one. For example, it may be possible to set destinations other than the host supervisory device 100 and transmit data sequentially to multiple destinations. The normal output line 13 between the CPU 3 and the public line modem 4 may be, for example, an RS232C or USB communication line. USB (Universal Serial Bus) is a registered trademark of Implementers Forum, Inc. in the United States.

The switching circuit 5 is a circuit configured by combining one or more selector switches, and maintains the connection between the RS232C line 11 and the input line 12 so that output from the PLC 9 is input to the CPU 3 when the CPU 3 is operating normally. Furthermore, when the CPU 3 is not operating normally (when stopped or hung up, etc.), the connection between the RS232C line 11 and the input line 12 is released, and the RS232C line 11 is connected to the bypass line 15.

In this way, if the CPU 3 in the telemeter communication device 2 is not operating normally, the switching circuit 5 switches to the connection line used in the event of a failure, i.e., the bypass line 15, and switches so that the data sequence 22 from the PLC 9 indicating the status of the pumping station is sent directly to the second input port 4b of the modem 4.

Figure 2 is a partial block diagram showing the internal configuration of the telemeter communication device 2 shown in Figure 1. The telemeter communication device 2 includes a CPU 3, a timer relay (TR) 8, and a switching circuit 5. TR 8 has an internal timer and maintains the output signal to the control signal line 17 at a high state when an external input signal (here, an operation signal from CPU 3 via operation signal line 16) is high. When the input signal from operation signal line 16 changes from high to low, the timer is activated, and after a predetermined time (e.g., several milliseconds to several seconds) has elapsed, the output signal to the control signal line 17 is switched from high to low, thereby switching the connection state of the switching circuit 5. Because TR 8 does not immediately stop outputting the signal output stop signal when normal operation signal reception is interrupted, the CPU 3 may temporarily enter a busy state due to processing requirements, preventing malfunction. In this embodiment, the CPU 3 may be equipped with an automatic recovery function that automatically resets the CPU 3 and returns it to its normal state if it hangs up for a long period of time. When the input signal from the operation signal line 16 changes from low to high, TR8 immediately switches the output signal to the control signal line 17 from low to high.

The switching circuit 5 is a switching unit comprising two relay-type changeover switches, a first relay 6 and a second relay 7. It outputs the input signal (RS232C line) to either the first output side (normal input line 12) or the second output side (bypass line 15) in accordance with an external control signal (here, the output of the timer relay 8 input via control signal line 17). A publicly known RS232C switch can be used. The first relay 6 is a contact-a switch that connects its contacts when an external control signal is received. The second relay 7 is a contact-b switch that connects its contacts when no external control signal is received.

Figure 2 (A) shows a case where CPU3 is operating normally. CPU3 continues to output a normal operation signal. When TR8 receives this normal operation signal, it outputs a high signal to switching circuit 5. Switching circuit 5 receives this signal and activates first relay 6 and second relay 7. When first relay 6 receives a control signal from TR8, the relay device operates, closing the previously open switch and connecting RS232C line 11 and input line 12 to CPU3 (contact a). At the same time, when second relay 7 receives a control signal from TR8, the relay device operates, opening the previously closed switch and disconnecting RS232C line 11 and bypass line 15 (contact b).

If CPU3 stops operating for some reason, as shown in Figure 3(B), the normal operation signal from CPU3 via operation signal line 16 disappears, and TR8 stops outputting signals to switching circuit 5 via control signal line 17 after a set time has elapsed since the normal operation signal was no longer received. As a result, the first relay 6 switches from closed to open, disconnecting the RS232C line 11 from the input line 12 to CPU3. At the same time, the second relay 7 switches from open to connect the RS232C line 11 to the bypass line 15.

In this embodiment, when CPU 3 operation stops and no signal is received from timer relay 8, switching circuit 5 automatically switches the output path of the abnormal signal from PLC 9 from CPU 3 to modem 4. Furthermore, when CPU 3 operation returns to normal, CPU 3 continues to output a normal operation signal to TR 8, and TR 8 is restored to the state shown in Figure 2(A) by switching circuit 5.

Figure 3 shows the transmission status of transmission data (telegrams) in an embodiment of the present invention. In PLC 9, the data string (transmission data 50) set by PLC 9 includes a status data section 51, which is a string of multiple bits indicating the status of each part of pump 40 when pump 40 fails. Figure 3 (A) shows the data transmission status when CPU 3 is operating normally. In a pumping station, when an abnormality occurs in pump 40, PLC 9, which monitors the status of pump 40, creates a data string indicating the status of each part and stores it in status data section 51 as transmission data 50, which is sent to telemeter communication device 2. In other words, transmission data 50 is the data string from PLC 9 itself. As shown in both Figures 3 (A) and (B), transmission data 50 created by PLC 9 is transmitted to telemeter communication device 2 via RS232C line 11.

In Figure 3 (A), CPU 3 is operating normally, so switching circuit 5 transmits the output of RS232C line 11 to input line 12 to CPU 3. CPU 3 performs the necessary data processing on the input status data section 51 and transmits it to modem 4 via the normal output line as transmission data 50. There are various possible data processing methods for status data section 51 that can be performed by CPU 3. The simplest example is a process in which transmission data 60 is created by adding a station data section 61 after status data section 51. Transmission data 60 is transmitted to modem 4 via normal output line 13, and modem 4 transmits transmission data 60 as is to the upper level supervisory device 100. The contents of transmission data 50 and 60 will now be further explained using Figure 4.

Figure 4 shows the contents of the transmission data 50, 60 shown in Figure 3, with (A) showing the transmission data 50 output from the PLC 9. The status data section 51 generated by the PLC 9 includes multiple bits 52a, 52b, 52c, etc. The number of bits included in the status data section 51 is arbitrary, for example 16 bits. The multiple bits 52a, 52b, 52c, etc. correspond to each part of the pump 40, and the status of each part is indicated by either "0" (normal) or "1" (abnormal).

Figure 4 (B) shows transmission data 60 sent to modem 4 after data processing by CPU 3. Here, CPU 3 performs processing to add a station data section 61 after status data section 51. Station data section 61 stores, for example, time data 62 indicating the date and time when PLC 9 detected the occurrence of a failure, and a machine number 63 indicating the equipment identification information of pump 40. The pumps 40 and machine numbers 63 located at the pump station are pre-registered in the host monitoring device 100. Therefore, upon receiving transmission data 60, host monitoring device 100 can determine which part of which pump 40 at which pump station the abnormality occurred, and when. The number of bits of the data string in station data section 61 can be any number, and may be around 16 or 32 bits, or even longer.

Returning to Figure 3, Figure 3(B) shows transmission data 50 sent from modem 4 to host supervisory device 100 when CPU 3 freezes or stops for some reason, such as a hang-up. When CPU 3 stops, transmission of transmission data 50 from CPU 3 to modem 4 becomes impossible. Therefore, in this embodiment, after a predetermined time has elapsed since CPU 3 stopped, the connection state of switching circuit 5 is switched from PLC 9 to bypass line 15. In this state, transmission data 50 output from PLC 9 is transmitted directly to the second input port 4b of modem 4 via bypass line 15 by switching circuit 5. When modem 4 receives transmission data 50 via bypass line 15, it establishes a communication path via a public line by calling host supervisory device 100, which is a preset destination, and transmits transmission data 50 directly to host supervisory device 100.

In this way, when the upper level monitoring device 100 receives transmission data 50 or 60 from the modem 4, it records the transmission data 50 or 60 together with the sender identification information in a storage device (not shown). Here, the sender identification information can be, for example, the telephone number of the modem 4 that made the call and the date and time of reception. As can be seen in Figure 3, there are two types of transmission data (50, 60) received by the upper level monitoring device 100. One is transmission data 60 received when the CPU 3 of the telemeter 1 is operating normally, and the other is transmission data 50 received when the CPU 3 is not operating normally. In this way, the upper level monitoring device 100 can easily identify whether the CPU 3 is stopped or not based on the difference in bit length of the transmission data 50, 60 and the content of a specific bit (here, the abnormal data section 55). In this embodiment, not only can it be easily determined whether the CPU 3 of the telemeter 1 is normal or not based on the difference between the received transmission data 50 (in the event of a malfunction) and transmission data 60 (in the normal state), but when abnormal transmission data 60 is received, the host monitoring device 100 can add date and time information, device information, etc., to fill in the missing data when the CPU 3 is stopped, and store it in a storage device (not shown).

Figure 5 shows the contents of transmission data 50A, 60A according to a first variant of the present invention. Transmission data 50A sent by PLC 9 is transmission data 50 shown in Figure 4 with one bit of abnormality data section 55 added. The configuration of status data section 51 is the same as transmission data 50 shown in Figure 4. Transmission data 50A is transmitted to CPU 3 with 16 bits of status data section 51 and one bit of abnormality data section 55 added by PLC 9. That is, in addition to the status data section 51 to be transmitted, PLC 9 adds abnormality data section 55 indicating the fault status of telemeter communication device 2 and outputs it as transmission data 50A. The abnormality data section 55 is identification data indicating whether or not the telemeter communication device 2 is faulty. If telemeter communication device 2 is normal, "0" is stored, and if an abnormality such as a stop or hang-up occurs, "1" is stored. When creating transmission data 50A, PLC 9 reserves a storage area for abnormal data section 55 and sets bit 55a to "1" as the default value. If telemeter communication device 2 is normal, when CPU 3 receives the data string (transmission data 50A) from PLC 9, it overwrites the contents of abnormal data section 55 with "0" indicating normality, adds station data section 61, and transmits the data to modem 4 as transmission data 60A. The contents of station data section 61 are the same as those shown in Figure 4. The transmission data 50A, with part of it rewritten in this way and the station data section 61 added, is then transmitted from modem 4 via public line 101 to host supervisory device 100 as transmission data 60A.

If the CPU 3 of the telemeter communication device 2 hangs up (stops), the transmission data 50A from the PLC 9 is sent directly to the modem 4 via the bypass line 15. The modem 4 then transmits the received transmission data 50A directly to the host monitoring device 100. The host monitoring device 100 can determine whether the CPU 3 of the telemeter communication device 2 is malfunctioning based on whether the content of bit 55a of the abnormality data section 55, which indicates the status of the CPU 3 of the telemeter communication device 2, is "1" or "0." The host monitoring device 100 then displays information or a warning indicating the malfunction on a display screen (not shown). In this way, even if the CPU 3 hangs up (stops), the transmission data 50A with the content of bit 55a set to "1" is sent to the host monitoring device 100, so the status of the pumping station can be communicated to the host monitoring device 100. The operator of the host monitoring device 100 can determine that a malfunction has occurred in the telemeter 1 at a specific remotely monitored object (e.g., a pumping station).

Figure 6 shows the contents of transmission data 50B, 60A according to a second variant of the present invention. As shown in Figure 6(A), transmission data 50B set by PLC 9 includes transmission data 50 shown in Figure 4, plus an abnormal data section 55, and a data area 56a for the additional data added by CPU 3 is reserved in advance. An initial value, for example, a series of "0" bits, is stored in data area 56a in advance. As a result, transmission data 50B sent from PLC 9 is approximately 32 bits long. The number of bits in abnormal data section 55 and empty data section 56 can be set arbitrarily, ranging from a few bytes to several tens of bytes, or even more.

The abnormal data section 55 has the same meaning as bit 55a shown in Figure 5. When the CPU 3 of the telemeter communication device 2 is normal, the transmission data 50B from the PLC 9 is transmitted to the CPU 3. When the CPU 3 creates transmission data 60A from transmission data 50B, it rewrites the content of the abnormal data section 55 from "1" (abnormal) to "0" (normal), and writes time data 62 and a machine number (equipment number) 63 indicating the station data into the empty data section 56. The content of the transmission data 60A after writing is the same as the transmission data 60A shown in Figure 5.

If the CPU 3 of the telemeter communication device 2 hangs up (stops), the transmission data 50B from the PLC 9 is sent directly to the modem 4 via the bypass line 15, and the modem 4 transmits the transmission data 50B to the host supervisory device 100. The host supervisory device 100 can unequivocally confirm that the telemeter communication device 2 is malfunctioning based on the contents of the abnormal data section 55, which indicates the status of the CPU 3 of the telemeter communication device 1, and can display information or a warning indicating the malfunction on a display screen (not shown). Furthermore, the host supervisory device 100 can determine whether the bit string following the abnormal data section 55, as well as the abnormal data section 55, is a sequence of consecutive zeros, and by confirming that information corresponding to the time data 62 and the serial number 63 is not present, it can confirm that the telemeter communication device 2 is malfunctioning. Furthermore, even if the abnormal data section 55 is omitted from the transmission data 50B and 60A in Figure 6, the host monitoring device 100 can determine that the telemeter communication device 2 is malfunctioning by determining whether the bit string following the abnormal data section 55 is a sequence of zeros.

As explained above, in variants 1 and 2 of this embodiment, the data string set by the PLC 9 includes an abnormality data section 55 indicating the state when the telemeter communication device fails, and the failure state is set in advance. Therefore, the upper level monitoring device 100 can determine whether the telemeter communication device 2 has failed by verifying the length of the transmitted transmission data 50A, 60A, the presence or absence of a bit "1" indicating an abnormality in the abnormality data section 55, or the contents of the data.

The present invention has been described above based on examples, but the present invention is not limited to the above examples and various modifications are possible within the scope of the invention.

1 Telemeter 2 Telemeter communication device 3 CPU
4 Modem 5 Switching circuit 6 First relay (a contact)
7 Second relay (b contact)
8 Timer relay 9 PLC
11 RS232C line 12 (normal) input line 13 normal output line 15 bypass line 16 operation signal line 17 control signal line 21 fault signal 22, 23 data string 24 normal transmission data 25 transmission data 40 pump 50, 50A, 50B transmission data (from PLC) 60 transmission data (from CPU) 100 upper level monitoring device 101 public line

Claims (12)

A telemeter having a telemeter communication device connected to a public line and a PLC that receives a fault signal from a monitored object and transmits the fault signal to the telemeter communication device,
the PLC has a function of outputting a data string indicating a fault state to the telemeter communication device when receiving the fault signal,
The telemeter communication device
a processor that receives the data string from the PLC and generates normal-time transmission data to be transmitted to a higher-level supervisory device;
a modem for the public line;
a switching unit for outputting a data stream from the PLC to either the processor or the modem;
A telemeter characterized by providing a bypass line for directly transmitting the data string from the PLC to the modem when the processor is not operating normally. The telemeter according to claim 1, characterized in that the switching unit has a changeover switch that connects the PLC to the processor when the processor is operating normally, and connects the PLC to the bypass line when the processor is not operating normally. The telemeter described in claim 2 is characterized in that it is provided with a timer relay that sends a control signal to control the changeover switch to connect the PLC and the processor when the processor is operating normally. The telemeter described in claim 3, characterized in that the changeover switch includes a first relay with an a-contact that connects the output of the PLC to the input line of the processor, and a second relay with a b-contact that connects the output of the PLC to the bypass line. The telemeter described in claim 4, characterized in that the processor creates the normal transmission data by adding additional information, including identification information and date and time information of the monitored object, to the data sequence received from the PLC. The telemeter of claim 5, wherein the modem, upon receiving the data stream via the bypass line, connects to a preset destination and automatically transmits the data stream. The telemeter described in claim 6, characterized in that the PLC includes identification data in the data string indicating that the telemeter communication device has a malfunction. The telemeter described in claim 7, characterized in that, upon receiving the data sequence from the PLC, the processor changes the identification data in the data sequence to identification data indicating that there is no fault. The telemeter described in claim 8, characterized in that the processor and the PLC are connected via an RS232C communication line, and the modem and the PLC are connected via an RS232C communication line. a PLC that receives a fault signal from a monitored object and outputs a data string including the fault signal;
A telemeter having a processor that generates transmission data to be transmitted from the output of the PLC to a host monitoring device, and a modem for a public line that connects the transmission data from the processor to a public line, and that transmits a signal indicating the status of a remotely monitored object to the host monitoring device using the modem,
a switching unit for switching between a communication line for transmitting the transmission data from the PLC to the modem and a bypass line for transmitting the transmission data from the PLC to the modem;
the switching unit connects the output of the PLC to the communication line when the processor is operating normally, and switches the output of the PLC to connect to the bypass line when the processor is not operating normally;
A communication method in a telemeter, characterized in that the modem establishes a communication path on the public line and transmits to the upper level monitoring device the transmission data from the processor or the data string transmitted from the PLC via the bypass line. The communication method for a telemeter described in claim 10, characterized in that the processor generates the transmission data by adding additional information to the PLC data string output via the switching unit. The modem has two input ports;
12. A telemeter communication method according to claim 11, wherein when the transmission data or the data string is input to any of the input ports via the bypass line, the transmission data or the data string is automatically transmitted by connecting to a predetermined destination.