Long-distance carrier digital call structure

Abstract

The invention relates to a long-distance carrier digital call structure, which comprises a low-voltage power supply and a plurality of digital telephones, and the low-voltage power supply and the digital telephones are connected with a carrier bus; wherein the digital telephone comprises a power supply base plate, an audio processing plate, a carrier communication plate and telephone input and output accessories, and the power supply base plate, the audio processing plate and the carrier communication plate are mutually connected through interfaces. By adopting the long-distance carrier digital call structure, the call system is free of a central node and a switch, low-voltage power supply is achieved, hot plugging can be achieved, and installation and maintenance are easy; the multi-party call can be realized at the same time, the longest communication distance between the telephones can reach several kilometers, any telephone can start broadcast at the same time in the call process, and the telephones of the whole system can receive the broadcast; a driver telephone is further arranged, the telephone can be inserted into a three-party call, and a whole-network alarm state can also be started.

Description

Technical Field

[0001] The invention relates to the field of digital calls, and in particular to a long-distance carrier digital call structure. Background Art

[0002] The communication distance of carrier digital telephone communication, the number of connected phones, the number of phones that can talk at the same time, and the ease of installation and maintenance have always been the core indicators for evaluating the quality of the carrier communication system. In the general process, the carrier signal is usually coupled to the power line. When the transmission distance is longer, the signal attenuation will become more serious. Therefore, the communication distance between points is limited. However, in order to extend the communication distance, a repeater is generally used to extend the signal. However, the separate access to the relay circuit board not only increases the system cost but also increases the difficulty of installation and maintenance.

[0003] Based on this, it is necessary to propose a solution to overcome the shortcomings of the current existing technology. Summary of the invention

[0004] The purpose of the present invention is to overcome the above-mentioned shortcomings of the prior art and provide a long-distance carrier digital call structure.

[0005] In order to achieve the above object, the long distance carrier digital call structure of the present invention is as follows:

[0006] The main feature of the long-distance carrier digital call structure is that the structure includes a low-voltage power supply and a plurality of digital telephones, and the low-voltage power supply and the digital telephones are both connected to the carrier bus; wherein,

[0007] The digital telephone comprises a power base plate, an audio processing board, a carrier communication board and telephone input and output accessories. The power base plate, the audio processing board and the carrier communication board are interconnected through interfaces.

[0008] Preferably, the power base plate obtains power from an external power cord, and is provided with an accessory interface, which includes a microphone access interface, a speaker interface, a switch signal interface and an LED display interface; the telephone input and output accessories include an external speaker, a handle, a built-in speaker, a foot switch, an alarm switch and an indicator light, and each accessory in the telephone input and output accessories is used to be connected to a corresponding interface in the accessory interface.

[0009] Preferably, the power base plate is also provided with a microphone output interface, an audio interface, an audio board communication port, a carrier board communication port, a power output port and a power input port, wherein the microphone output interface, the audio interface and the audio board communication port are respectively connected to the microphone input interface, the audio output interface and the base plate communication interface on the audio board, and the carrier board communication port and the power output port are respectively connected to the base plate communication port and the power input port on the carrier board; the power input port is connected to an external power cord, and the power output port is also used to connect to the next digital telephone.

[0010] Preferably, the power baseboard also includes a power conversion circuit, which converts the input power into the power required by each board, wherein the power conversion circuit includes a power amplifier circuit, a multi-way selection circuit and an MCU. The MCU obtains a switch signal and controls a display signal, and sends each sound source input by the audio processing board to the power amplifier circuit through the multi-way selection circuit, and the power amplifier circuit drives each speaker on the speaker interface; the MCU is also connected to the switch signal interface and the LED display interface to drive and implement corresponding switch instructions and / or LED indication instructions.

[0011] Preferably, the audio processing board includes a power conditioning circuit. When the microphone signal is obtained, it enters the AGC circuit through the internal microphone selection switch, and then is sent to the echo noise elimination DSP by the audio filter amplifier circuit for processing. The echo noise elimination DSP simultaneously obtains the background sound input by the background sound microphone interface for input noise elimination processing, and then inputs the processed audio signal into the vocoder for encoding and decoding processing and then sends it to the MCU. The MCU communicates with the power baseboard and then sends the processed signal to the far end. The baseboard communication interface feeds back the obtained far-end audio to the MCU, and then the MCU sends it to the vocoder for decoding. The audio signal after decoding processing is sent to the echo noise elimination DSP, and the echo noise elimination DSP compares the input and output signals and performs corresponding echo elimination processing, wherein the processed signal is sent to the far-end audio output interface through the audio filter amplifier circuit; the signal sent by the echo noise elimination DSP to the vocoder before decoding is output to the near-end audio output interface through the filter amplifier circuit;

[0012] It also includes an alarm urging audio output interface and an alarm urging sound recording port, wherein the alarm urging sound is synthesized by the MCU control, and the synthesized sound is recorded into the external storage through the alarm urging sound recording port.

[0013] Preferably, the carrier communication board directly draws power from the power line and supplies power after rectifier and filter power conversion. The remote voice carrier signal on the power line enters the analog front-end circuit through the input coupling circuit and the input filter circuit, and communicates with the power line carrier core inside the MCU through the interface, and then informs the digital telephone through the bottom board communication interface; and

[0014] The local voice signal obtained from the power baseboard communicates with the analog front-end circuit through the power line carrier core. After the analog front-end circuit outputs the signal differentially, it is coupled to the power line through the output filter circuit, the output coupling circuit and the coil, thereby realizing full-duplex bidirectional communication.

[0015] The long-distance carrier digital call structure of the present invention has no central node, no switch, low-voltage power supply, hot-swappable, and simple installation and maintenance. The structure does not specify the wiring method, and communication can be achieved by simply hanging it on the power supply line, which simplifies installation and maintenance. The number of telephones connected to the system at the same time can reach dozens, which can meet most application scenarios; multi-party calls can be realized at the same time (limited to a maximum of three parties at the same time due to the influence of carrier bandwidth); telephones at any location can be interchanged, and installation and maintenance are further simplified; the longest communication distance between telephones can reach several kilometers; and during a call, any telephone can start broadcasting at the same time, and all telephones in the system can receive the broadcasting; and a driver's telephone is set in the system, which can be inserted into a three-party call and can also start the alarm state of the entire network. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a schematic block diagram of the long-distance carrier digital call structure of the present invention.

[0017] Figure 2 The figure is a schematic diagram of the structure of a single digital telephone of the present invention.

[0018] Figure 3 It is a schematic diagram of the composition structure of the power base plate of the present invention.

[0019] Figure 4 The figure is a schematic diagram of the structure of the audio processing board of the present invention.

[0020] Figure 5 It is a schematic diagram of the composition structure of the carrier communication board of the present invention.

[0021] Figure 6 A schematic diagram of the data structure for communication between the carrier communication board and the power baseboard defined in the present invention.

[0022] Figure 7 A schematic diagram of the application layer design task of the carrier communication board of the present invention.

[0023] Figure 8 The figure is a schematic diagram of a possible digital telephone wiring method in practical application of the long-distance carrier digital communication system of the present invention.

[0024] Fig. 9 It is a schematic diagram of the data structure of the carrier receiving and transmitting frame of the present invention.

[0025] Fig.10 It is a schematic diagram of a data source information list of the present invention.

[0026] Fig.11 The present invention is a flowchart of the process of carrier frame generation and transmission.

[0027] Fig.12 This is a flow chart of the update process of the data source list of the present invention.

[0028] Fig.13 It is a schematic diagram of the worst wiring method in practical application of the long-distance carrier digital communication system of the present invention.

[0029] Fig.14 This is a flow chart for calculating the sending time point within the cycle of the present invention.

[0030] Fig.15 The figure is a schematic diagram of verifying a three-party conversation in actual application of the long-distance carrier digital conversation system of the present invention. DETAILED DESCRIPTION

[0031] In order to more clearly describe the technical content of the present invention, further description is given below in conjunction with specific embodiments.

[0032] Before describing in detail embodiments according to the present invention, it should be noted that, hereinafter, the terms "comprises", "includes" or any other variations are intended to cover non-exclusive inclusion, whereby a process, method, article or apparatus comprising a series of elements includes not only these elements, but also other elements not explicitly listed or inherent to such process, method, article or apparatus.

[0033] See also Figure 1 As shown, the long-distance carrier digital call structure, wherein the structure includes a low-voltage power supply and a plurality of digital telephones, and the low-voltage power supply and the digital telephones are connected to the carrier bus; wherein,

[0034] The digital telephone comprises a power base plate, an audio processing board, a carrier communication board and telephone input and output accessories. The power base plate, the audio processing board and the carrier communication board are interconnected through interfaces.

[0035] As a preferred embodiment of the present invention, the power base plate obtains power from an external power cord, and is provided with an accessory interface, which includes a microphone access interface, a speaker interface, a switch signal interface and an LED display interface; the telephone input and output accessories include an external speaker, a handle, a built-in speaker, a foot switch, an alarm switch and an indicator light, and each accessory in the telephone input and output accessories is used to be connected to the corresponding interface in the accessory interface.

[0036] As a preferred embodiment of the present invention, the power base plate is also provided with a microphone output interface, an audio interface, an audio board communication port, a carrier board communication port, a power output port and a power input port, wherein the microphone output interface, the audio interface and the audio board communication port are respectively connected to the microphone input interface, the audio output interface and the base plate communication interface on the audio board, and the carrier board communication port and the power output port are respectively connected to the base plate communication port and the power input port on the carrier board; the power input port is connected to an external power cord, and the power output port is also used to connect to the next digital telephone.

[0037] As a preferred embodiment of the present invention, the power baseboard also includes a power conversion circuit, which converts the input power into the power required by each board, wherein the power conversion circuit includes a power amplifier circuit, a multi-way selection circuit and an MCU. The MCU obtains a switch signal and controls a display signal, and sends each sound source input by the audio processing board to the power amplifier circuit through the multi-way selection circuit, and the power amplifier circuit drives each speaker on the speaker interface; the MCU is also connected to the switch signal interface and the LED display interface to drive and implement corresponding switch instructions and / or LED indication instructions.

[0038] As a preferred embodiment of the present invention, the audio processing board includes a power conditioning circuit. When the microphone signal is obtained, it enters the AGC circuit through the internally arranged microphone selection switch, and then is sent to the echo noise elimination DSP by the audio filter amplifier circuit for processing. The echo noise elimination DSP simultaneously obtains the background sound input by the background sound microphone interface for input noise elimination processing, and then inputs the processed audio signal into the vocoder for encoding and decoding processing and then sends it to the MCU. The MCU communicates with the power baseboard and then sends the processed signal to the far end. The baseboard communication interface feeds back the obtained far-end audio to the MCU, and then the MCU sends it to the vocoder for decoding. The audio signal after decoding processing is sent to the echo noise elimination DSP, and the echo noise elimination DSP compares the input and output signals and performs corresponding echo elimination processing, wherein the processed signal is sent to the far-end audio output interface through the audio filter amplifier circuit; the signal sent by the echo noise elimination DSP to the vocoder before decoding is output to the near-end audio output interface through the filter amplifier circuit;

[0039] It also includes an alarm urging audio output interface and an alarm urging sound recording port, wherein the alarm urging sound is synthesized by the MCU control, and the synthesized sound is recorded into the external storage through the alarm urging sound recording port.

[0040] As a preferred embodiment of the present invention, the carrier communication board directly draws power from the power line, and supplies power after rectifier and filter power conversion. The remote voice carrier signal on the power line enters the analog front-end circuit through the input coupling circuit and the input filter circuit, and communicates with the power line carrier core inside the MCU through the interface, and then informs the digital telephone through the bottom board communication interface; and

[0041] The local voice signal obtained from the power baseboard communicates with the analog front-end circuit through the power line carrier core. After the analog front-end circuit outputs the signal differentially, it is coupled to the power line through the output filter circuit, the output coupling circuit and the coil, thereby realizing full-duplex bidirectional communication.

[0042] like Figure 1 As shown, the design has a simple structure and only includes a low-voltage power supply and multiple digital telephones. It has no requirements for wiring methods and is very simple to install and maintain. Among them, the power supply line is the communication line.

[0043] In order to achieve multi-party calls, a higher audio compression rate consumes less transmission bandwidth. Therefore, this technical solution uses a high audio compression dedicated DSP, which can generate a frame of audio code with only 6 bytes every 20ms.

[0044] On this basis, the transmission control on the carrier power line is the core part of this technical solution. In order to facilitate installation and maintenance, digital telephones need to be interchangeable at will. Therefore, the serial port is used for transmission between the carrier board and the bottom instead of the network port, bypassing the configuration of the IP address, which can also save hardware costs.

[0045] In this communication system, each telephone node realizes the function of mutual relay through software. Since the IP protocol is not used, the link layer of the carrier can be programmed directly. Because the IP layer is bypassed and the MAC address is used directly for distinction, there is no need to configure the IP address during construction, and the installation and maintenance of the telephone will be extremely simple.

[0046] In this regard, the design goal of this technical solution is: any phone can initiate a call, and through broadcasting, call the other phone to start the call. After the other phone picks up the phone, the two parties enter the call. If other devices continue to pick up the phone, a multi-party call can be started. A maximum of three people can talk. After more than three parties, the phone that picks up the phone later enters the urging state. If the phone that picks up the phone later is the driver's phone, one of the devices will be kicked out, and the three-party call will still be retained. During the call, if any phone presses the broadcast button, the phone will become a shouting phone, and the remaining phones in the entire network that have not picked up the phone will broadcast the voice of the shouting phone. The driver's phone is also equipped with an alarm pedal. At any time, the alarm pedal will cause all network devices to enter the alarm state and play the alarm audio.

[0047] Therefore, the phone is in four states at any time: on-hook monitoring state, alarm state, talking (shouting) state, and urging to hang up state. The switching of the four states is not only related to the switch state of the phone (including off-hook, broadcast button, alarm switch, driver configuration), but also related to the occupation of the carrier line by other phones on the bus.

[0048] Therefore, the carrier board software application layer of the present invention needs to transmit the status and audio data obtained by the local telephone from the baseboard, and also control the telephone's occupation of the carrier line.

[0049] like Figure 6 As shown, serial communication is carried out between the carrier communication board and the power baseboard. The communication content includes time, switch status, audio data, as well as the bus occupancy mode sent from the baseboard to the carrier board and the local setting control returned by the carrier board to the baseboard.

[0050] The carrier board communicates with the base board. Every time the base board produces a new voice packet, it will send the data to the carrier board. The carrier board will cache the data and send it at the appropriate time. The communication data structure is as follows: Figure 6 .

[0051] The appropriate sending time is very important for communication. If it is not properly controlled, data conflicts are likely to occur on the network, affecting the sending and receiving results.

[0052] The carrier board will receive data sent by other machines on the carrier bus, and its format is also Figure 6 After obtaining the data from other machines, it may be forwarded, and the baseboard will be notified to change the state of the local machine or modify the list of other machines on the baseboard.

[0053] For this reason, Figure 7 As shown, the software of the carrier board application layer is designed with three tasks, including the baseboard serial port receiving task, the carrier data receiving task and the carrier active sending task.

[0054] In a specific embodiment of the present invention, for better explanation, there is provided Figure 8 A possible wiring method is shown, its problems are pointed out, and a solution is given.

[0055] Figure 8 This is a possible way to wire telephones. Assuming that the longest distance of the carrier is 300 meters, since the point-to-point distance is within the range, telephone 1 can communicate normally with its neighbor telephone 3, but not with telephones 2 and 4. Similarly, telephone 3 can communicate normally with telephone 1, telephone 2, telephone 4, and telephone 6, but not with other telephones. In order to broadcast the entire network, the command frame and data frame of telephone 1 need to pass through telephone 1, telephone 3, telephone 6, and telephone 9 before reaching telephone 10 and telephone 8. It can be seen that during the transmission process, some telephones must forward the source data to achieve full network broadcasting.

[0056] Because the wiring cannot be predicted, the present invention requires that each telephone must broadcast and forward the data source once. However, at this time, for telephone 6, in addition to a frame of data sent by telephone 3 during data downlink, telephone 5, telephone 7, and telephone 9 will also forward data frames. Phone 6 will receive data frames sent by the data source multiple times. Without a reasonable mechanism, phone 6 will repeatedly send the frame, and other phones will also repeat it, resulting in serious bus congestion and communication jam.

[0057] exist Figure 8 In the example, the phenomenon of phone 6 will also occur in phone 3 and phone 9. With more complicated wiring, the above situation is more serious.

[0058] Therefore, a reasonable mechanism needs to be designed to ensure that each phone can forward once and only once during the communication process to ensure smooth communication. To this end, the present invention introduces a data source + data identification method to achieve the above goal.

[0059] Based on this, we first define the transceiver frame format of the carrier link layer. The transceiver frame format is defined as follows: Fig. 9 As shown, the data source information list is as follows Fig.10 shown.

[0060] To generate the carrier frame, just follow Fig.10 Just fill in the data in the corresponding position as shown. To prevent frame transmission errors, a CRC check is added to the end of the frame. There is an 8-byte frame source identifier in the data structure. This identifier is used for forwarding control. In order to avoid the trouble caused by data overflow of this identifier, an 8-byte integer is directly defined. When each node sends a new frame of data, the identifier will be incremented.

[0061] Figure 8 In the process, a node may receive data from the same data source multiple times from neighboring nodes.

[0062] During the receiving process, the carrier will enter the data source and identifier into the data source table. When a new frame of data is received, it can compare whether the identifier in the same data source is the latest. If and only if the identifier of the latest data source is the latest, the frame of data will be processed. This ensures that each phone sends and forwards the frame of each data source only once.

[0063] In this way, the bandwidth can be reasonably utilized during the transmission of a frame of data, without excessive occupancy and without loss.

[0064] The update flow chart of the data source list is as follows: Fig.12 As shown in the figure, after the above design, a frame of data can be transmitted smoothly between all phones. However, when multiple nodes send data at the same time, bus conflicts are still inevitable, resulting in audio loss during the transmission of multiple phones. Figure 7 The sending time control described in is the key to coordinating multi-machine calls.

[0065] The key to solving this problem is to divide the multi-device calls into time slices. In each time slice, only one data source phone can broadcast to the entire network. Three devices are needed to talk, which is divided into four time slices with some margin.

[0066] go through Fig.12 After the data source list is updated, all call nodes will exist in the table. A benchmark is needed for the sending time point. First, the call devices in the list are sorted according to the size of the mac address. The largest mac address is identified as the benchmark for the sending time. The second ranked device is offset by one time slice after the sending time of the largest mac address, the third ranked device is offset by two time slices, and the fourth ranked device is offset by three time slices. The number of devices that can talk at the same time is limited to three. In the worst case, if the fourth device is inserted into the call, one of them will be kicked out. It can be seen that four time slices are sufficient.

[0067] The time of each time slice can be determined according to Figure 8, increase attenuation on the lines between each phone to ensure that each device can only send signals to neighboring devices.

[0068] Fig.13 This is the worst wiring method for 30 devices to talk. The carrier communication has the most forwarding times. The sending and receiving time between phone 1 and phone 30 is measured. This time can be customized as the time slice for the communication of the 30 phones.

[0069] Of course, the time slice is also affected by the load of a frame of data. The greater the load, the more bandwidth resources are occupied. The load can be adjusted in the subsequent test process.

[0070] Fig.14 To calculate the sending time point flow chart within the cycle, this process is called when the carrier acquires a new frame. With the sending time, Figure 7 In the carrier active sending task, it is determined whether the sending time point has arrived. Only when the bus needs to be occupied and the sending time point has arrived, will it be sent.

[0071] With the above design, when multiple parties are talking, the carrier bus will send data from each party in an orderly manner, and the buses will not conflict with each other.

[0072] Therefore, when 30 telephones are hung on the bus, the 30 telephones are relays for each other, the point-to-point distance is 300 meters, and the maximum transmission distance will increase to 9000 meters. The simulation increases the transmission impedance so that each telephone can only directly transmit with two adjacent nodes. Since the nodes in the present invention play the role of mutual relay, when the audio time carried by each frame is 400ms, three telephones talk without any pressure on the bus, and the audio loss time is 0 in one hour. The verification results are as follows Fig.15 shown.

[0073] During an audio call, the voice frames after audio encoding actually contain many silent frames and comfortable noise frames. Moreover, during a three-party call, the three parties will not speak separately, and there will always be someone speaking and someone listening. Therefore, in order to further save the bandwidth resources of the carrier, the present invention also marks the silent frames and comfortable noise frames during the audio transmission process instead of transmitting the complete frames. At the recipient's end, they are re-synthesized according to the marks, and the system performance is further optimized.

[0074] Any process or method description in a flowchart or otherwise described herein may be understood to represent a module, segment or portion of code that includes one or more executable instructions for implementing the steps of a specific logical function or process, and the scope of the preferred embodiments of the present invention includes alternative implementations in which functions may not be performed in the order shown or discussed, including performing functions in a substantially simultaneous manner or in the reverse order depending on the functions involved, which should be understood by those skilled in the art to which the embodiments of the present invention belong.

[0075] It should be understood that each part of the present invention can be implemented by hardware, software, firmware or a combination thereof. In the above embodiments, multiple steps or methods can be implemented by software or firmware stored in a memory and executed by a suitable instruction execution device.

[0076] A person of ordinary skill in the art may understand that all or part of the steps of the method for implementing the above-mentioned embodiment may be completed by instructing the relevant hardware through a program, and the program may be stored in a computer-readable storage medium, which, when executed, includes one of the steps of the method embodiment or a combination thereof.

[0077] The storage medium mentioned above can be a read-only memory, a magnetic disk or an optical disk, etc.

[0078] In the description of this specification, the description with reference to the terms "an embodiment", "some embodiments", "example", "specific example", or "embodiment" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0079] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

[0080] The long-distance carrier digital call structure of the present invention has no central node, no switch, low-voltage power supply, hot-swappable, and simple installation and maintenance. The structure does not specify the wiring method, and communication can be achieved by simply hanging it on the power supply line, which simplifies installation and maintenance. The number of telephones connected to the system at the same time can reach dozens, which can meet most application scenarios; multi-party calls can be realized at the same time (limited to a maximum of three parties at the same time due to the influence of carrier bandwidth); telephones at any location can be interchanged, and installation and maintenance are further simplified; the longest communication distance between telephones can reach several kilometers; and during a call, any telephone can start broadcasting at the same time, and all telephones in the system can receive the broadcasting; and a driver's telephone is set in the system, which can be inserted into a three-party call and can also start the alarm state of the entire network.

[0081] In this specification, the present invention has been described with reference to specific embodiments thereof. However, it is apparent that various modifications and variations may be made without departing from the spirit and scope of the present invention. Therefore, the specification and drawings should be regarded as illustrative rather than restrictive.

Claims

1. A long-distance carrier digital call structure, characterized in that: The structure includes a low voltage power supply and a plurality of digital telephones, and the low voltage power supply and the digital telephones are connected to a carrier bus; wherein, The digital telephone comprises a power base plate, an audio processing board, a carrier communication board and telephone input and output accessories. The power base plate, the audio processing board and the carrier communication board are interconnected through interfaces.

2. The long distance carrier digital call structure according to claim 1, characterized in that: The power base plate obtains power from an external power cord, and is provided with an accessory interface, which includes a microphone access interface, a speaker interface, a switch signal interface, and an LED display interface; the telephone input and output accessories include an external speaker, a handle, a built-in speaker, a foot switch, an alarm switch, and an indicator light, and each accessory in the telephone input and output accessories is used to be connected to a corresponding interface in the accessory interface.

3. The long distance carrier digital call structure according to claim 2, characterized in that: The power base plate is also provided with a microphone output interface, an audio interface, an audio board communication port, a carrier board communication port, a power output port and a power input port, wherein the microphone output interface, the audio interface and the audio board communication port are respectively connected to the microphone input interface, the audio output interface and the base plate communication interface on the audio board, and the carrier board communication port and the power output port are respectively connected to the base plate communication port and the power input port on the carrier board; the power input port is connected to an external power cord, and the power output port is also used to connect to the next digital telephone.

4. The long distance carrier digital call structure according to claim 2, characterized in that: The power baseboard also includes a power conversion circuit, which converts the input power into the power required by each board, wherein the power conversion circuit includes a power amplifier circuit, a multi-way selection circuit and an MCU. The MCU obtains a switch signal and controls a display signal, and sends each sound source input by the audio processing board to the power amplifier circuit through the multi-way selection circuit, and the power amplifier circuit drives each speaker on the speaker interface; the MCU is also connected to the switch signal interface and the LED display interface to drive and implement corresponding switch instructions and / or LED indication instructions.

5. The long distance carrier digital call structure according to claim 1, characterized in that: The audio processing board includes a power conditioning circuit. When the microphone signal is obtained, it enters the AGC circuit through the internal microphone selection switch, and then is sent to the echo noise elimination DSP by the audio filter amplifier circuit for processing. The echo noise elimination DSP simultaneously obtains the background sound input by the background sound microphone interface for input noise elimination processing, and then inputs the processed audio signal into the vocoder for encoding and decoding processing and then sends it to the MCU. The MCU communicates with the power baseboard and then sends the processed signal to the far end. The baseboard communication interface feeds back the obtained far-end audio to the MCU, and then the MCU sends it to the vocoder for decoding. The audio signal after decoding processing is sent to the echo noise elimination DSP, and the echo noise elimination DSP compares the input and output signals and performs corresponding echo elimination processing, wherein the processed signal is sent to the far-end audio output interface through the audio filter amplifier circuit; the signal sent by the echo noise elimination DSP to the vocoder before decoding is output to the near-end audio output interface through the filter amplifier circuit; It also includes an alarm urging audio output interface and an alarm urging sound recording port, wherein the alarm urging sound is synthesized by the MCU control, and the synthesized sound is recorded into the external storage through the alarm urging sound recording port.

6. The long distance carrier digital call structure according to claim 1, characterized in that: The carrier communication board is powered directly from the power line and is powered after being rectified and filtered. The remote voice carrier signal on the power line enters the analog front-end circuit through the input coupling circuit and the input filtering circuit, and communicates with the power line carrier core inside the MCU through the interface, and then informs the digital telephone through the bottom board communication interface; and The local voice signal obtained from the power baseboard communicates with the analog front-end circuit through the power line carrier core. After the analog front-end circuit outputs the signal differentially, it is coupled to the power line through the output filter circuit, the output coupling circuit and the coil, thereby realizing full-duplex bidirectional communication.

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