JPS61237550A - Multiplex transmission equipment - Google Patents

Abstract

PURPOSE:To make multiplex transmission with a simple circuit by making the primary station connected in loop with plural number of secondary stations send the reset signal, checking and memorizing the connection state of the secondary stations and transmitting/receiving the data by sending poling signal. CONSTITUTION:Plural number of secondary stations 2-6 are connected in loop to a primary station 1 by a two-core transmission cable. The primary station 1 sends a reset signal transmission line 7, and memorizes the number of secondary stations being connected and their types, whether transmission type or reception type. Next, it sends poling signal and trigger signal, and at the same time when it receives data from transmission type secondary stations, it sends data to reception type secondary stations according to the trigger signal. After receiving the poling signal, the transmission type secondary station sends out its own data following the trigger signal, while reception type secondary station receives the poling signal and then sends the trigger signal and then receives the data from the primary station. In this way, multiplex transmission can be done easily even when transmission type and reception type secondary stations are mixed up.

Description

[Detailed Description of the Invention] [Field of the Invention] The present invention is constructed by connecting a primary station (master station) and a plurality of secondary stations (slave stations) in a digital chain manner using a dedicated two-core wire. This invention relates to a multiplex transmission device.

[Summary of the invention]

The multiplex transmission device according to the present invention sends out a polling signal and a trigger signal after sending out a reset signal, determines the type of connected secondary station based on the presence or absence of a data signal, and then determines the type of connected secondary station depending on the connected secondary station. A primary station is provided that transmits polling signals and trigger signals, receives data signals from a transmitting secondary station, and transmits data when a receiving secondary station is connected, and transmits a digital signal to the primary station. A transmitting type secondary station that is connected in a continuous loop in a chain type and receives a polling signal from a higher priority station and sends out data, and a receiving type 2 station that receives a data signal after receiving a polling signal from a higher priority station.
A transmission device is formed by the next station. Such a configuration eliminates the need to set addresses for individual secondary stations, and it becomes possible to connect a mixture of transmitting and receiving type secondary stations.

[Prior art and its problems]

In general, in multiplex transmission equipment that configures a data transmission system by connecting a primary station and multiple secondary stations with a two-core dedicated line, the secondary stations are connected to any point on the common bus. A multi-drop system is often used, and in this case it is necessary to set a unique address for each secondary station. Such address settings are normally made using a DIP switch or the like provided at each secondary station.

However, when it is necessary to make the secondary station extremely compact, there is a problem in that the DIP switch limits the miniaturization. Furthermore, when setting up a large number of secondary stations at once, setting addresses is relatively easy, but when increasing or decreasing the number of secondary stations after configuring the multiplex transmission equipment system, the addresses may not be consecutive. Furthermore, there is a possibility that a plurality of secondary stations may be set to the same address by mistake, resulting in a transmission error. In addition, a shift register method is known in which addresses are not specified for each secondary station in order to facilitate work at the site where secondary stations are installed, but this method requires a signal line for clock signals in addition to data signals. Therefore, a transmission system cannot be constructed using inexpensive two-core wires, and there is a problem in that the price of the transmission cable increases.

There are two types of secondary stations: a receiving type secondary station that receives data from the primary station and drives a relay, etc., and a transmitting type secondary station that is connected to a sensor etc. and transmits data to the primary station. However, with conventional multiplex transmission equipment, it is difficult to configure a transmission equipment by mixing these, and the problem is that the connection order must be stored in the primary station, which complicates the system configuration. there were.

[Purpose of the invention]

The present invention has been made in view of the problems of the conventional multiplex transmission device, and uses DIP switches to
It is not necessary to set an address for the next station (we provide a multiplex transmission device that can be configured by mixing a transmitting type secondary station and a receiving type secondary station in the same loop and connecting them with a two-core transmission cable. The purpose is to

[Structure and effects of the invention]

The present invention is a multiplex transmission device in which a primary station and a plurality of secondary stations are loop-connected in a digital chain manner via a transmission line, and the primary station transmits a polling signal, which is the right to transmit and receive, to the secondary station having the highest priority. A polling signal sending means for sending out a polling signal to the station, a reset signal sending means for sending a reset signal when the connection state of the secondary station is detected, and a polling signal sending means for sending out a reset signal when the connection state of the secondary station is detected.
A secondary station discrimination means detects and stores the type of the next station, and a data signal obtained from the transmission line when a transmitting type secondary station is connected is detected by the secondary station discrimination means during data transmission with the secondary station. comprising a data receiving means for receiving data, and a data signal transmitting means for transmitting a data signal to the receiving type secondary station based on the determination by the secondary station determining means during data transmission with the secondary station,
Each secondary station is connected between input and output, and includes a filter means that passes the data signal, reset signal, and trigger signal obtained from the input terminal and blocks the polling signal, a holding means that receives the reset signal and holds this signal, and a holding means that receives the reset signal and holds this signal. Receiving means for receiving a data signal after receiving a polling signal and a trigger signal when the reset signal is not held by the means, and transmitting a polling signal to a subsequent station and a trigger signal to a primary station after receiving the data signal by the receiving means. a receiving type secondary station having a polling/trigger signal sending means for transmitting a polling/trigger signal; a filtering means connected between input/output for transmitting a data signal, a reset signal, and a trigger signal obtained from an input terminal and blocking a polling signal; A transmitting type secondary station having a receiving means for receiving a trigger signal, a transmitting means for transmitting a data signal to the primary station after receiving the polling signal and the trigger signal, and subsequently transmitting the polling signal and the trigger signal. It is characterized by being connected.

According to the present invention having such characteristics, a reset signal, a polling signal, a data signal, and a trigger signal are transmitted using a two-core transmission line, and the transmitting type secondary station transmits the trigger signal to the trigger signal after receiving the polling signal. Next, the data of its own station is sent onto the transmission line, and the receiving secondary station does not perform any receiving operation during training scan after receiving the polling signal, but during normal operation, it sends out a trigger signal after receiving the polling signal and the primary station Data transmission is performed with the primary station by receiving data from the station. When each secondary station completes its operation, it sequentially transmits a polling signal, which gives it the right to transmit and receive, to secondary stations in the subsequent order. This configuration allows transmitting and receiving secondary stations to be connected on the same loop, and there is no need to detect which station is connected at the time of connection; the primary station automatically detects the connection. can do. Therefore, it is possible to mix transmission/reception type secondary stations and perform data transmission between the primary station and the secondary station using only two-core transmission lines. Furthermore, since addresses are not set for each secondary station, there is no need to provide a DTP switch.

Therefore, each secondary station can be downsized, and workability when installing the secondary stations can be improved.

[Explanation of Examples]

FIG. 1 is a schematic block diagram showing an embodiment of a multiplex transmission apparatus according to the present invention. In this figure, primary station 1 and multiple 2
The next stations 2, 3, 4, 5, and 6 are connected in a loop in a digital chain by a two-core transmission line 7. That is, the output terminal 1-o of the primary station is connected to the input terminal 2-i of the secondary station 2 connected to the highest order, and the output terminal 2-o of the secondary station 2 is connected to the next It is connected to the input terminal 3-i of the secondary station 3. Similarly, the output terminal 3-o of the secondary station 3 is connected to the input terminal 4-i of the secondary station 4, and the output terminal 4-o is connected to the input terminal 4-i of the secondary station 5.
The output terminal 5-o is connected to the input terminal 5-i of the 2
It is connected to the input terminal 6-i of the next station 6. The output terminal 6-o of the last secondary station 6 is connected to the input terminal 1-i of the primary station 1 via a transmission line 7. The primary station 1 sends a reset signal to the transmission line 7, then transmits a polling signal that gives the right to transmit and receive to the secondary station with the highest priority, and sequentially stores the number of connected secondary stations and their transmission/reception types. At the same time,
Thereafter, after sending out the polling signal and the trigger signal, data is sequentially received from the multiplication type secondary station, and data is sent to the receiving type secondary station in response to the trigger signal. Here 2
Next stations 2.3 and 5 are transmitting type secondary stations, and secondary stations 4 and 6 are receiving type secondary stations, and these transmitting and receiving type secondary stations are mixed and connected in a digital chain by transmission line 7. It is assumed that there is

(Configuration of Primary Station) As shown in FIG. 2, the primary station 1 includes a reset signal transmitting circuit 11. which operates based on an external start signal. A polling signal detection circuit 12 and a gate circuit 13 that is reset by a start signal. Memory 14.15
and an address counter 16. The polling signal detection circuit 12 provides a start signal to the polling trigger signal transmission circuit 17 at the start of operation. The polling signal detection circuit 12 detects a polling signal obtained from the input terminal 1-i of the primary station 1, and when detecting the polling signal, outputs a 1-scan completion signal to the outside.

Reset signal transmission circuit 11. A clock signal is applied to the polling trigger signal transmission circuit 17 from an oscillator 18 . The reset signal transmitting circuit 11 has a frequency of 60, for example.
A reset signal for each secondary station is sent to the transmission line 7 using an NRZ code modulated by a KHz signal, and the reset signal sending timing is given to the polling/trigger signal sending circuit 17. The polling/trigger signal transmitting circuit 17 outputs a polling signal modulated with a frequency of, for example, IMHz and a trigger signal based on an NRZ code with a frequency of 60 KHz to an output terminal 1-.

It is sent from A data signal receiving/reproducing circuit 19 and a trigger signal receiving circuit 20 are connected to the input terminal 1-i. The trigger signal receiving circuit 20 uses a polling trigger signal transmitting circuit 17 to receive a reception prohibition signal when transmitting a trigger signal.
It receives a trigger signal given via the transmission line 7 and gives the received output as a counting input to the address counter 16 and also outputs it to the memory 15.

Further, the data signal receiving/reproducing circuit 19 receives the data signal from the secondary station provided through the input terminal 1-i, reproduces it as a data output, and also supplies the received signal to the memory 15. The address counter 16 is a counter that counts the addresses of the secondary stations connected on the transmission line 7 and performing data transmission with the primary station, and outputs the count output to the outside and provides it to the memories 14 and 15. Memory 14 is a memory that stores the number of secondary stations connected to transmission A7, and memory 14 is a memory that stores the number of secondary stations connected to transmission A7.
5 holds data on the types of connected secondary stations, ie, transmission type and reception type, and the output thereof is displayed on the display unit 2.
It is given to 1. Further, the gate circuit 13 operates a data signal receiving/reproducing circuit 19 and a data signal transmitting circuit 2 according to the count value of the address counter 16 and the contents stored in the memories 14 and 15.
1 are given a reception permission signal and a transmission permission signal respectively to selectively operate them. The data signal transmitting circuit 22 is for transmitting a data signal to a receiving type secondary station when that station is connected.

(Configuration of Transmission Type Secondary Station) FIG. 3 is a block diagram showing the configuration of the transmission type secondary station 2, and the other secondary stations 3 and 5 have similar configurations. Now, the input terminal 2-4 of the secondary station 2 includes a low-pass filter 31 and a reset signal receiving circuit 32. A polling signal detection circuit 33 and a trigger signal reception circuit 34 are connected. The low-pass filter 31 is a passive filter consisting of an LC, which blocks a signal with a frequency of IMHz used as a polling signal regardless of the power supply state, and cuts off a signal with a frequency of IMHz or less given from the transmission line 7, for example 60 KH.
The data signal, reset signal, and trigger signal modulated by z are transmitted as they are to the output terminal 2-o.

Further, the polling signal detection circuit 33 receives the polling signal applied via the transmission line 7, and provides the detection timing to the trigger signal receiving circuit 34.

The trigger signal receiving circuit 34 receives the trigger signal applied from the transmission line 7, and provides the reception timing to the data polling trigger signal transmitting circuit 35. The data/polling/trigger signal transmitting circuit 35 is a transmitting circuit that sequentially transmits a data signal/polling signal and a trigger signal from the output terminal 2-o in response to a transmission clock provided by the oscillator 36. The outputs of the low-pass filter 31 and the transmitting circuit 35 are connected to the subsequent secondary station 3 via the output terminal 2-o.

(Configuration of Reception Type Secondary Station) FIG. 4 is a block diagram showing the configuration of the reception type secondary station 4, and the reception type secondary station 6 also has a similar configuration. Now, the input terminal 4-i of the secondary station 4 is connected to a low-pass filter 41 and a reset signal receiving circuit 42. A polling signal detection circuit 43 and a trigger data signal receiving circuit 44 are connected. The low-pass filter 41 is a filter that blocks high-frequency signals used as boring signals, similar to the above-described low-pass filter 31. The reset signal receiving circuit 42 is a receiving circuit that receives a reset signal given from the primary station 1 during a training operation, and the received output is given to a training flag 45 and a data reproducing circuit 46. The polling signal detection circuit 43 receives the boring signal and provides detection timing to the trigger data signal receiving circuit 44. After receiving the trigger signal, the trigger data signal receiving circuit 44 gives an output to the oscillator 47 to start oscillation, transmits the received data to the outside via the data reproducing circuit 46, and polls and triggers the timing after the reception is completed. The signal is applied to the signal transmitting circuit 48. The training flag 45 is a flag that is reset when a signal is given twice from the polling signal detection circuit 43. If the flag is set, the operation of the data reproducing circuit 46 is prohibited, and the polling signal is stopped by the trigger signal reception completion pulse. The trigger signal transmission circuit 48 is operated. The polling/trigger signal transmitting circuit 48 sequentially transmits a boring signal with a frequency of IMHz and a trigger signal with a frequency of 60 KHz onto the transmission line 7. The data signal reproducing circuit 46 decodes and outputs the data signal, and its output is used as a drive signal for different output means, such as relays, for each secondary station.

(Operation of this embodiment) Next, the operation of this embodiment will be described with reference to flowcharts and waveform diagrams. FIG. 5 is a flowchart showing the operation of the primary station 1, and FIGS. 6(a) to 6(f) are waveform diagrams showing signal waveforms at each point of a w f shown in FIG. In this figure, when a start signal is given to the primary station 1, a training scan operation is first performed to determine the type of connected secondary station, and the gate circuit 13. The memory 14,15 and address counter 16 are reset (step 51). At the same time, a start signal is given to the reset signal transmitting circuit 11, and a reset signal R is sent from the primary station 1 to the transmission line 7 at time t1, as shown in FIG. 6 (δ).
1 is sent (step 52). The sending timing is then transmitted to the polling/trigger signal transmitting circuit 17, and as shown in FIG. 6(a), the boring signal P1 and trigger signal T1 are sent to the transmission line 7 (step 53).
). Then, in steps 54, 55 and 58, it is checked whether a polling signal, data signal or trigger signal is received from the sensing and receiving circuit connected to the input terminal 1-i. The boring signal P1 is transmitted to the highest priority secondary station 2 connected to the output terminal 1-o of the primary station 1, and is detected by the polling signal detection circuit 33.

As mentioned above, since the boring signal is modulated with a high frequency of frequency IMllz, it is not transmitted to the subsequent secondary stations 3 and onward as shown in FIG.

At the secondary station 2, the detection timing of the boring signal is transmitted to the trigger signal receiving circuit 34. When the trigger signal TI sent from the primary station 1 is received, the reception timing is determined by the data polling trigger signal transmitting circuit 35.
can be conveyed to. Therefore, as shown in FIG. 6 (bl), the data signal D2 is sent out from the secondary station 2 to the transmission line 7, and furthermore, the boring signal P2 and the trigger signal T2 are sent out in sequence.

This data signal D2 passes through the low-pass filter of each secondary station, is received by the data signal receiving/reproducing circuit 19 of the primary station 1, and is output. If the data signal is received by primary station 1, the sending type secondary station is connected, so step 5
Step 5 proceeds to step 56, and the trigger signal receiving circuit 20 waits for reception of a trigger signal (step 56).
- If the IJ signal is received, store "H" in the memory 15 corresponding to the address of the address counter 16 at that time, that is, that a transmitting type secondary station is connected (Step 57), and proceed to Step 60. Then, the address counter 16 is incremented and the process returns to step 54. Since the secondary station 3 is also a transmission type secondary station, it receives the boring signal P2 from the secondary station 2 as shown in FIG. The signal D3 is sent out onto the transmission line 7, and subsequently the boring signal P3 and the trigger signal T3 are sent out.At this time, the process returns to step 54 via steps 54 to 57 and 60, and the same process is repeated.

Now, the secondary station 4 is a receiving type secondary station, and the reset signal R1
Upon reception of the training flag 45, the training flag 45 is set and data reproduction is prohibited. Therefore, after the polling signal P3 from the second station 3 is detected, the detection timing is given to the trigger data signal receiving circuit 44. After receiving the trigger signal T3, a transmission timing is given to the polling trigger signal transmission circuit 48. Therefore, as shown in FIG. 6(d), the secondary station 4
A polling signal P4 and a trigger signal T4 are sequentially sent out. As mentioned above, the polling signal P4 is blocked by the low-pass filter and is not transmitted to the primary station l, but the trigger signal T4 is received by the trigger signal receiving circuit 20 of the primary station l and proceeds from steps 58 to 59 to be stored in the memory 15. “
L" is set and the address counter 16 is incremented (step 60), and the process returns to step 54 to repeat the same process. Since the secondary station 5 is a transmitting type secondary station, the secondary station 2.3 Similarly, polling signal P4
In response to the trigger signal T4, it sends the data D5 to the primary station 1, and also gives the polling signal P5 and trigger signal T5 to the secondary station in the succeeding order. The secondary station 6 sends a polling signal P6 based on these signals as shown in FIG. 6(f).
and sends out a trigger signal T6.

Secondary station 6 is the last secondary station and polling P6 is 1.
The signal is transmitted to the next station 1 and detected by the polling signal detection circuit 11. Therefore, the process advances from step 54 to step 61, and the contents of the memory 15 at this time are displayed on the display section 21 as shown in FIG.

The process then proceeds to step 62, where the count value of the address counter 16 is set in the memory 14, the number of secondary stations is held in the memory 14, and the training scan operation (time Tt) is completed.

Next, the normal data transmission cycle begins, and in step 63, the address counter 16 is reset, and in step 64, the address counter 16 is reset.
In response to the detection output from the polling signal detection circuit 12, the polling/trigger signal transmission circuit 17 sends the signal as shown in FIG.
As shown in a), the polling signal P1 and the trigger signal T
Sends 1. Now, the process proceeds to step 65, and it is checked whether the count value of the address counter 16 matches the data in the memory 14. If they do not match, the process proceeds to step 66, and the data in the memory 15 indicated by the address counter 16 is "H". Check if it exists. This is “H”
If so, since the transmitting type secondary station is connected, reception is permitted by the gate circuit 13, and the process advances to step 67 to check whether a data signal has been received. The transmission type secondary station receives the polling signal and the training signal and sends out the data signal onto the transmission line in the same way as during the training scan described above, and also sends out the polling signal to the secondary stations connected in the subsequent order. Therefore, the primary station 1 checks whether a data signal has been received from the data signal receiving/reproducing circuit 19, and if so, proceeds to step 69 and checks whether a trigger signal has been received from the trigger signal receiving circuit 20. . As shown in FIG. 2(b), when the trigger signal T2 is sent out from the secondary station 2, the process proceeds to step 70, where the counter 16 is incremented, and the process returns to step 65. The same operation is repeated for the secondary station 3, and the primary station sequentially receives data from the transmitting secondary station. If the stored content of the memory 15 is 4L'' in step 66, the gate circuit 13 permits transmission, and the process proceeds to step 68, where the data signal transmission circuit 22 sends the data to the secondary station 4 as shown in FIG. 6(a). Send data signal D4.2
Since the training flag 45 of the next station 4 is reset by the detection of the polling signal P3, the next station 4 receives and reproduces the data signal D4 from the trigger/data signal receiving circuit 44, and also receives the polling signal P4 and the data signal D4 from the polling/trigger signal transmitting circuit 4. Trigger T4 is sent out sequentially. The primary station 1 receives this trigger signal T4, increments the counter 16, and repeats the same process.

In this way, based on the stored contents of the memory 15, the transmitting/receiving type 2
Identify the next station and perform data transmission. When data transmission to all secondary stations is completed, the contents of the memory 14 and the count value of the address counter 16 match, so the process proceeds from step 65 to step 71, where the polling signal is checked by the polling signal detection circuit 12, and the polling signal is checked. If the signal P6 is received, a one scan completion signal is sent out (step 72), and the process returns to step 63 to repeat the same process in the next cycle.

In this way, the primary station 1 receives a data signal every time a trigger signal is given, or transmits data to the secondary station according to the connection checked by a training scan after sending out a polling signal, thereby controlling the transmission type and reception type. 2
Even when a mixture of secondary stations is connected to a two-core transmission line, it is possible to automatically identify the type of secondary station and perform data transmission without setting addresses for each secondary station.

In this embodiment, a multiplex transmission apparatus using five secondary stations has been described, but it goes without saying that a similar system can be constructed using an even larger number of secondary stations. Furthermore, in this embodiment, a low-pass filter is provided in each secondary station to pass the data signal, trigger signal, and reset signal as they are and to block only the polling signal. .

By modulating the reset signal with a high frequency, it is also possible to change the filter that only blocks the polling signal to a filter such as a bypass filter.

[Brief explanation of the drawing]

FIG. 1 is a schematic block diagram showing an embodiment of a multiplex transmission device according to the present invention, and FIG. 2 is a schematic block diagram showing an embodiment of a multiplex transmission device according to the present invention.
FIG. 3 is a block diagram showing the configuration of the next station I, FIG. 3 is a block diagram showing the configuration of the transmitting type secondary station, FIG. 4 is a block diagram showing the configuration of the receiving type secondary station, and FIG.
The figure is a flowchart showing the operation of the primary station l, FIG. 6 is a waveform diagram showing the waveforms of each part a% f of the transmission line of the multiplex transmission device, and FIG. FIG. 1-・-Primary station 2, 3, 4, 5.6--------2
Next game? ---------1 transmission line 11--------
・Reset signal transmission circuit 12, 33, 43--
-------Polling signal detection circuit 13----
--Gate circuit 14.15...-Memory 16-
...-address counter 17, 48----
Polling/trigger signal transmitting circuit 19-- Data signal receiving/reproducing circuit 2 tl----------
Trigger signal receiving circuit 22---1---Data signal transmitting circuit 31゜41---M-Low pass filter 32, 42--Reset signal receiving circuit 35----- --- Data polling trigger signal transmission circuit 44 --- Trigger data signal receiving circuit 45 --- Training flag 48 --- Polling trigger signal transmitting circuit Patent applicant Tateishi Denki Co., Ltd. agent Patent attorney Yoshiki Okamoto (and 1 other person) Figure 1 Figure 4 Otsu 1 Procedures Amendment (voluntary) 1 Indication of the case 1985 Patent Application No. 078945 24 Name of the invention Multiplex transmission device 3. Relationship with the case of the person making the amendment Patent applicant address 10 Hanazono Tsuchido-cho, Ukyo-ku, Kyoto-shi, Kyoto Name (294) Tateishi Electric Co., Ltd. Representative Takao Miki 4 Agent address 550 Osaka, Osaka, Osaka Prefecture 5, 3rd floor, Shinkosan Building, 1-13-38 Nishihonmachi, Nishi-ku, Ichi, Column 6 of the detailed description of the invention in the specification subject to amendment? ! Correct contents (1) The description of r60KHzJ on page 11, line 14, page 11, line 20 to page 12, line 1, page 13, line 19, and page 16, line 3, has been changed to r60KHz and 30. K.H.
z Correct it as J. (2) rN on page 11, line 15 of the specification box, and page 12, line 1
The description of ``RZ code'' will be corrected to ``biphase code.'' (3) “Figure 2 (
b) Correct the description of J to "In Figure 6)". that's all

Claims (2)

[Claims] (1) A multiplex transmission device in which a primary station and a plurality of secondary stations are loop-connected in a digital chain manner via a transmission line, and the primary station transmits a polling signal, which is the right to transmit and receive, to the two stations with the highest priority. A polling signal transmitting means for transmitting to the next station; a reset signal transmitting means for transmitting a reset signal when the connection state of the secondary station is detected; and after transmitting the reset signal, detecting and storing the type of the secondary station based on the presence or absence of a data signal. a secondary station determining means; and a data receiving means for receiving a data signal obtained from a transmission line when a transmitting type secondary station is connected by the secondary station determining means during data transmission with the secondary station; and data signal sending means for sending a data signal to the receiving type secondary station based on the determination by the secondary station determining means during data transmission with the next station, and each of the secondary stations has a The data signal obtained from the connected input terminal,
filter means for passing the reset signal and the trigger signal and blocking the polling signal; holding means for receiving the reset signal and holding the signal; and after receiving the polling signal and the trigger signal when the reset signal is not held by the holding means. a receiving type secondary station having receiving means for receiving a data signal, and polling/trigger signal transmitting means for transmitting a polling signal to a subsequent station and a trigger signal to the primary station after receiving the data signal by the receiving means; A data signal connected between the outputs and obtained from the input terminal,
Filter means for passing the reset signal and trigger signal and blocking the polling signal; receiving means for receiving the polling signal and trigger signal; and transmitting the data signal to the primary station after receiving the polling signal and the trigger signal, and then transmitting the polling signal and the trigger signal. 1. A multiplex transmission device, characterized in that it is connected in a mixed manner to a transmitting type secondary station having a transmitting means for transmitting. (2) The polling signal sent out by the polling signal sending means of the primary station and each of the secondary stations is a data signal;
The multiplex transmission according to claim 1, wherein the signal has a higher frequency than the reset signal and the trigger signal, and the filter means of each secondary station is a low-pass filter that blocks only the polling signal. Device.