Long-distance carrier digital call system

Abstract

The present invention relates to a long-distance carrier digital call system, comprising a low-voltage power supply and a plurality of digital telephones, wherein the low-voltage power supply and the digital telephones are both connected to a carrier bus; each digital telephone comprises a power supply baseboard, an audio processing board, a carrier communication board, and a telephone input / output accessory; the power supply baseboard, the audio processing board, and the carrier communication board are all connected to each other by means of an interface; serial communication is performed between the power supply baseboard and the carrier communication board, communication content comprising time, an on / off state, audio data, a bus occupation mode sent to the carrier communication board from the power supply baseboard, and a local setting control mode returned to the power supply baseboard by the carrier communication board. The long-distance carrier digital call system of the present invention has no central node and no switch, and features low-voltage power supply, hot pluggability, and simple installation and maintenance; multi-party calls can be realized within the same time; and the longest communication distance between telephones can reach several kilometers.

Description

Long-distance carrier digital communication system

[0001] Cross-references to related applications

[0002] This application claims priority to Chinese Patent Application No. 202411801413.X, filed on December 9, 2024, the contents of which are incorporated herein by reference. Technical Field

[0003] This invention relates to the field of digital communication, specifically to a long-distance carrier digital communication system. Background Technology

[0004] The communication distance, the number of connected handsets, the number of handsets that can talk simultaneously, and the ease of installation and maintenance of carrier digital telephone communication have always been core indicators for evaluating the quality of a carrier communication system. In general processing, the carrier signal is usually coupled to the power line, and signal attenuation becomes more severe as the transmission distance increases. Therefore, the communication distance between points is limited. However, to extend the communication distance, repeaters are generally used to extend the signal; however, connecting a separate repeater circuit board not only increases system costs but also increases the difficulty of installation and maintenance.

[0005] Therefore, it is necessary to propose a solution to overcome the shortcomings of the current existing technology. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide a long-distance carrier digital communication system.

[0007] To achieve the above objectives, the long-distance carrier digital communication system of the present invention is as follows:

[0008] This long-distance carrier digital communication system is characterized by comprising a low-voltage power supply and several digital telephones, all of which are connected to a carrier bus. Each digital telephone includes a power supply baseboard, an audio processing board, a carrier communication board, and telephone input / output accessories. The power supply baseboard, audio processing board, and carrier communication board are interconnected via interfaces. The power supply baseboard and the carrier communication board communicate via serial port, with communication content including time, switch status, audio data, bus occupancy information sent from the power supply baseboard to the carrier communication board, and local setting control information returned from the carrier communication board to the power supply baseboard.

[0009] Preferably, the system's application layer software for the carrier communication board includes a baseboard serial port receiving task, with the following processing flow:

[0010] (1.1) The carrier communication board receives the task and determines whether there is a data frame from the power supply base. If not, the step is repeated; otherwise, proceed to (1.2).

[0011] (1.2) Determine whether the current data frame is an AT command frame. If it is, execute the corresponding AT command; otherwise, proceed directly to (1.3).

[0012] (1.3) Determine again whether the data frame of the power supply base is included. If yes, cache the data of the power supply base. Otherwise, return to step (1.1).

[0013] Preferably, the system has a carrier data reception task designed in the application layer software of the carrier communication board, and the processing flow is as follows:

[0014] (2.1) Start the carrier reception task and determine whether there is a carrier frame. If not, repeat the step; otherwise, proceed directly to (2.2).

[0015] (2.2) The process of extracting carrier data, controlling the transmission time, updating the data list, obtaining the bus occupancy mode of other machines, setting the local status and other machine table, forwarding carrier data, and sending the data of other machines to the power supply baseboard is executed in sequence to complete the reception of carrier data.

[0016] Preferably, the system's application layer software for the carrier communication board is designed with a carrier active transmission task, and the processing flow is as follows:

[0017] (3.1) Start executing the carrier active transmission task, extract the current operating status of the digital telephone and generate the carrier occupancy control word;

[0018] (3.2) Determine whether the carrier line needs to be occupied for task transmission. If not, perform short delay processing directly; otherwise, proceed to (3.3).

[0019] (3.3) Determine whether the current corresponding task's transmission time has arrived. If so, perform carrier transmission processing and then perform short delay. Otherwise, perform short delay processing directly.

[0020] Preferably, the carrier frame is generated and transmitted in the following manner:

[0021] (2.1.1) The carrier transmission task for receiving instructions or data begins;

[0022] (2.1.2) Set the address, identifier, and sending station address of the next station, and fill in the pass-through word and magic word;

[0023] (2.1.3) Set the current frame as a downlink frame and set the data source address;

[0024] (2.1.4) Fill the load with serial port buffer and calculate the cyclic redundancy check code (CRC), the load, and the number of frame bytes;

[0025] (2.1.5) Carrier transmission: The carrier transmission task for the corresponding command or data ends.

[0026] Preferably, when the carrier acquires a new frame, the transmission time point is calculated as follows:

[0027] (2.2.1) Start calculating the transmission time point;

[0028] (2.2.2) Sort the current data source list and calculate the sorted sequence number of the received frame data source;

[0029] (2.2.3) Determine if the current data source sequence number is the largest. If it is, the reference at the current sending time point is the remainder of the system time % sending period. Otherwise, the current reference remains unchanged.

[0030] (2.2.4) Calculate the sequence number after sorting on the local machine, and determine whether the current local sequence number is the largest. If it is, the sending time point = (base time + sequence number × time slice)% sending period; otherwise, the local sending time point is not adjusted.

[0031] (2.2.5) The calculation of the sending time point ends.

[0032] Preferably, the carrier data source list is updated in the following manner;

[0033] (2.3.1) Start updating the data source list;

[0034] (2.3.2) Determine if the current data source address exists. If not, a new data source needs to be added; otherwise, proceed directly to (2.3.3).

[0035] (2.3.3) Determine if the current identifier is new. If not, end the list update directly. Otherwise, proceed to (2.3.4).

[0036] (2.3.4) Calculate the current identifier interval, where the number of missing audio frames is the difference between the old and new identifiers;

[0037] (2.3.5) Determine if there is a missing frame. If so, calculate the missing audio time and accumulate the missing audio time. Otherwise, proceed directly to (2.3.6).

[0038] (2.3.6) Determine if the current interval time is larger. If it is, replace the maximum identifier interval first. Otherwise, directly record the system time of the current identifier.

[0039] (2.3.7) Set the remaining time for deleting the data source and end the data source list update.

[0040] The long-distance carrier digital communication system of this invention has no central node, no exchange, low-voltage power supply, is hot-swappable, and is simple to install and maintain. The system does not specify wiring methods; it only needs to be connected to the power supply line to communicate, further simplifying installation and maintenance. The system can simultaneously connect to dozens of phones, meeting most application needs; it can achieve multi-party calls at the same time (limited to a maximum of three parties due to carrier bandwidth limitations); phones in any location can be interchanged, further simplifying installation and maintenance; the longest communication distance between phones can reach several kilometers; and during a call, any phone can simultaneously activate a broadcast, which can be received by all phones in the system; the system also includes a driver's phone, which can be inserted into a three-way call and can also activate a network-wide alarm. Attached Figure Description

[0041] Figure 1 is a structural block diagram of the long-distance carrier digital communication system of the present invention.

[0042] Figure 2 is a schematic diagram of the composition structure of a single digital telephone according to the present invention.

[0043] Figure 3 is a schematic diagram of the composition structure of the power supply base plate of the present invention.

[0044] Figure 4 is a schematic diagram of the composition structure of the audio processing board of the present invention.

[0045] Figure 5 is a schematic diagram of the composition structure of the carrier communication board of the present invention.

[0046] Figure 6 is a schematic diagram of the data structure for communication between the carrier communication board and the power supply baseboard as defined in this invention.

[0047] Figure 7 is a schematic diagram of the application layer design task of the carrier communication board of the present invention.

[0048] Figure 8 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.

[0049] Figure 9 is a schematic diagram of the data structure of the carrier transceiver frame of the present invention.

[0050] Figure 10 is a schematic diagram of the data source information list of the present invention.

[0051] Figure 11 is a flowchart of the carrier frame generation and transmission process of the present invention.

[0052] Figure 12 is a flowchart of the data source list update process of the present invention.

[0053] Figure 13 is a schematic diagram of the worst wiring method in practical application of the long-distance carrier digital communication system of the present invention.

[0054] Figure 14 is a flowchart of the calculation at the transmission time point within the cycle of the present invention.

[0055] Figure 15 is a schematic diagram of the long-distance carrier digital communication system of the present invention verifying three-way communication in practical application. Detailed Implementation

[0056] To more clearly describe the technical content of the present invention, the following description is provided in conjunction with specific embodiments.

[0057] Before describing the embodiments of the present invention in detail, it should be noted that, in the following, the terms “comprising,” “including,” or any other variations are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed or inherent to such process, method, article, or apparatus.

[0058] Please refer to Figure 1. This long-distance carrier digital communication system includes a low-voltage power supply and several digital telephones, all of which are connected to a carrier bus. Each digital telephone includes a power supply baseboard, an audio processing board, a carrier communication board, and telephone input / output accessories. The power supply baseboard, audio processing board, and carrier communication board are interconnected via interfaces. The power supply baseboard and the carrier communication board communicate via serial port. The communication content includes time, switch status, audio data, bus occupancy mode sent from the power supply baseboard to the carrier communication board, and local setting control mode returned from the carrier communication board to the power supply baseboard.

[0059] In a preferred embodiment of the present invention, the system has a baseboard serial port receiving task designed for the application layer software of the carrier communication board, and the processing flow is as follows:

[0060] (1.1) The carrier communication board receives the task and determines whether there is a data frame from the power supply base. If not, the step is repeated; otherwise, proceed to (1.2).

[0061] (1.2) Determine whether the current data frame is an AT command frame. If it is, execute the corresponding AT command; otherwise, proceed directly to (1.3).

[0062] (1.3) Determine again whether the data frame of the power supply base is included. If yes, cache the data of the power supply base. Otherwise, return to step (1.1).

[0063] In a preferred embodiment of the present invention, the system has a carrier data reception task designed in the application layer software of the carrier communication board, and the processing flow is as follows:

[0064] (2.1) Start the carrier reception task and determine whether there is a carrier frame. If not, repeat the step; otherwise, proceed directly to (2.2).

[0065] (2.2) The process of extracting carrier data, controlling the transmission time, updating the data list, obtaining the bus occupancy mode of other machines, setting the local status and other machine table, forwarding carrier data, and sending the data of other machines to the power supply baseboard is executed in sequence to complete the reception of carrier data.

[0066] In a preferred embodiment of the present invention, the system has an active carrier transmission task designed in the application layer software of the carrier communication board, and the processing flow is as follows:

[0067] (3.1) Start executing the carrier active transmission task, extract the current operating status of the digital telephone and generate the carrier occupancy control word;

[0068] (3.2) Determine whether the carrier line needs to be occupied for task transmission. If not, perform short delay processing directly; otherwise, proceed to (3.3).

[0069] (3.3) Determine whether the current corresponding task's transmission time has arrived. If so, perform carrier transmission processing and then perform short delay. Otherwise, perform short delay processing directly.

[0070] In a preferred embodiment of the present invention, the carrier frame is generated and transmitted in the following manner:

[0071] (2.1.1) The carrier transmission task for receiving instructions or data begins;

[0072] (2.1.2) Set the address, identifier, and sending station address of the next station, and fill in the pass-through word and magic word;

[0073] (2.1.3) Set the current frame as a downlink frame and set the data source address;

[0074] (2.1.4) Fill the load with serial port buffer and calculate the cyclic redundancy check code (CRC), the load, and the number of frame bytes;

[0075] (2.1.5) Carrier transmission: The carrier transmission task for the corresponding command or data ends.

[0076] In a preferred embodiment of the present invention, when the carrier acquires a new frame, the transmission time point is calculated in the following manner:

[0077] (2.2.1) Start calculating the transmission time point;

[0078] (2.2.2) Sort the current data source list and calculate the sorted sequence number of the received frame data source;

[0079] (2.2.3) Determine if the current data source sequence number is the largest. If it is, the reference at the current sending time point is the remainder of the system time % sending period. Otherwise, the current reference remains unchanged.

[0080] (2.2.4) Calculate the sequence number after sorting on the local machine, and determine whether the current local sequence number is the largest. If it is, the sending time point = (base time + sequence number × time slice)% sending period; otherwise, the local sending time point is not adjusted.

[0081] (2.2.5) The calculation of the sending time point ends.

[0082] In a preferred embodiment of the present invention, the carrier data source list is updated in the following manner;

[0083] (2.3.1) Start updating the data source list;

[0084] (2.3.2) Determine if the current data source address exists. If not, a new data source needs to be added; otherwise, proceed directly to (2.3.3).

[0085] (2.3.3) Determine if the current identifier is new. If not, end the list update directly. Otherwise, proceed to (2.3.4).

[0086] (2.3.4) Calculate the current identifier interval, where the number of missing audio frames is the difference between the old and new identifiers;

[0087] (2.3.5) Determine if there is a missing frame. If so, calculate the missing audio time and accumulate the missing audio time. Otherwise, proceed directly to (2.3.6).

[0088] (2.3.6) Determine if the current interval time is larger. If it is, replace the maximum identifier interval first. Otherwise, directly record the system time of the current identifier.

[0089] (2.3.7) Set the remaining time for deleting the data source and end the data source list update.

[0090] As shown in Figure 1, the system has a simple structure, consisting of only a low-voltage power supply and multiple digital telephones. It has no requirements for the wiring method and is very simple to install and maintain. The power supply line is also the communication line.

[0091] To enable multi-party communication, a higher audio compression rate consumes less transmission bandwidth. Therefore, this technical solution uses a high-performance dedicated audio compression DSP, which can generate a 6-byte audio encoding frame every 20ms.

[0092] Based on this, the transmission control on the carrier power line is the core of this technical solution. In order to simplify installation and maintenance, digital telephones need to be interchangeable. Therefore, serial port is used for transmission between the carrier board and the bottom instead of network port, which bypasses the configuration of IP address and saves hardware costs.

[0093] In this communication system, each telephone node functions as a relay for others 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 differentiation, there is no need to configure IP addresses during construction, making the installation and maintenance of the telephones extremely simple.

[0094] The design goal of this technical solution is as follows: Any phone can initiate a call and broadcast a message to other phones to join the call. Once another phone picks up, both parties enter the call. If other devices continue to pick up, multi-party calls can be initiated, with a maximum of three people in a call. After three parties, the phone that picks up last enters a hang-up notification state. If the phone that picks up last is the driver's phone, one of the devices is disconnected, but the three-way call is still maintained. During a call, if any phone presses the broadcast button, that phone becomes the broadcast phone, and all remaining phones on the network that are not picked up will broadcast the broadcast message. Furthermore, the driver's phone is equipped with an alarm foot pedal. At any time, activating the alarm pedal will put all devices on the network into alarm mode and play an alarm audio.

[0095] Therefore, a telephone is in one of four states at any given time: on-hook monitoring, alarm state, call (speaking) state, and call-to-hang-up state. The switching between these four states is related not only to the telephone's on / off status (including off-hook, broadcast button, alarm switch, and driver configuration), but also to the carrier line usage of other telephones on the bus.

[0096] Therefore, the carrier board software application layer of this invention needs to transmit the status and audio data obtained by the local telephone from the baseboard, while also controlling the telephone's occupation of the carrier line.

[0097] As shown in Figure 6, the carrier communication board communicates with the power supply baseboard via serial port. 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 settings control returned by the carrier board to the baseboard.

[0098] The carrier board communicates with the baseboard. When the baseboard generates a new voice packet, it sends the data to the carrier board. The carrier board will buffer the data and send it at the appropriate time. The data structure of the communication is shown in Figure 6.

[0099] The timing of sending data is crucial for communication; if not properly controlled, data conflicts can easily occur on the network, affecting the results of sending and receiving.

[0100] The carrier board receives data sent from other machines on the carrier bus, and the format is the data structure described in Figure 6. After receiving the data from other machines, it may forward it and simultaneously notify the backplane to change its own status or modify the backplane's list of other machines.

[0101] To this end, as shown in Figure 7, the software design of the carrier board application layer includes three tasks: the baseboard serial port reception task, the carrier data reception task, and the carrier active transmission task.

[0102] In a specific embodiment of the present invention, for better illustration, a possible wiring method as shown in FIG8 is provided, its problems are pointed out, and a solution is given.

[0103] Figure 8 illustrates a possible telephone wiring configuration. Assuming the maximum carrier distance is 300 meters, since the point-to-point distances are all within this 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 telephones 1, 2, 4, and 6, but not with other telephones. For network-wide broadcasting to be possible, the command and data frames from telephone 1 must pass through telephones 1, 3, 6, and 9 before reaching telephones 10 and 8. Therefore, during transmission, some telephones must forward the source data to achieve network-wide broadcasting.

[0104] Because the wiring is unpredictable, this invention requires each phone to broadcast and forward the data source once. However, for phone 6, in addition to phone 3 sending a data frame during the downlink process, phones 5, 7, and 9 will also forward the data frame. Phone 6 will receive the data frame from the data source multiple times. Without a reasonable mechanism, phone 6 will repeatedly send the frame, and other phones will also send the same frame repeatedly, resulting in severe bus congestion and communication blockage.

[0105] In Figure 8, the same phenomenon observed with phone 6 will also occur with phones 3 and 9. With more complex wiring, the situation becomes even more severe.

[0106] Therefore, a reasonable mechanism needs to be designed to ensure that each phone can forward data once, and only once, during the communication process to ensure smooth communication. To this end, this invention introduces a data source + data identifier method to achieve the above objective.

[0107] Accordingly, the transmit and receive frame format of the carrier link layer is first defined. The transmit and receive frame format definition is shown in Figure 9, and the data source information list is shown in Figure 10.

[0108] The generation of carrier frames simply requires filling in the data at the corresponding positions as shown in Figure 10. To prevent frame transmission errors, a CRC checksum is added to the end of the frame. The data structure contains an 8-byte frame source identifier. This identifier is used for forwarding control. To avoid the problems caused by data overflow of this identifier, an 8-byte integer is directly defined. Each node increments the identifier when sending a new frame of data.

[0109] In Figure 8, a node may receive data from the same data source multiple times from neighboring nodes.

[0110] During the reception process, the carrier records 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. The frame of data will only be processed if the identifier of the latest data source is received. This ensures that each phone forwards each data source frame only once.

[0111] In this way, bandwidth is used efficiently during the transmission of a single frame of data, ensuring that it is neither overused nor missed.

[0112] The update flowchart of the data source list is shown in Figure 12. With the above design, a single data frame can be transmitted smoothly among all phones. However, when multiple nodes send data simultaneously, bus conflicts are still unavoidable, causing audio loss during the transmission of multiple phones. Therefore, the transmission timing control described in Figure 7 is crucial for coordinating multi-phone calls.

[0113] The core solution to this problem is to divide multi-device calls into time slices. Within each time slice, only one data source phone can broadcast across the entire network. If three devices are needed to make a call, the time slices should be divided into four time slices, with some margin.

[0114] After updating the data source list in Figure 12, all call nodes will exist in this table. A baseline is needed for the transmission time. First, the call devices in the list are sorted by MAC address size, with the largest MAC address as the baseline for transmission time. The second-ranked device is shifted one time slice after the transmission time of the largest MAC address, the third-ranked device is shifted two time slices, and the fourth-ranked device is shifted three time slices. This limits the number of devices in a simultaneous call to three. In the worst-case scenario, if a fourth device inserts a call, one of the devices will be removed. Therefore, dividing the call into four time slices is sufficient.

[0115] The timing of each time slice can be determined according to Figure 8. Attenuation is added to the lines between each phone to ensure that each device can only send messages to neighboring devices.

[0116] Figure 13 shows the worst wiring configuration for 30 devices communicating, where the carrier communication has the most forwarding times. The transmission and reception times of telephone 1 and telephone 30 are measured, and this time can be customized to allow for communication time slices for all 30 telephones.

[0117] Of course, the time slice is also affected by the load of a single frame of data; the higher the load, the more bandwidth resources are consumed. The load can be adjusted during subsequent testing.

[0118] Figure 14 is a flowchart for calculating the transmission time point within the period. This process is called when the carrier acquires a new frame. With the transmission time point in hand, in Figure 7, the carrier-initiated transmission task determines whether the transmission time point has arrived. Transmission only occurs when the bus needs to be occupied and the transmission time point has arrived.

[0119] With the above design, during multi-party calls, the carrier bus will send data to each party in an orderly manner, and the buses will not conflict with each other.

[0120] Therefore, when 30 phones are connected to the bus, and these 30 phones act as relays to each other, with a point-to-point distance of 300 meters, the maximum transmission distance will increase to 9000 meters. By simulating increased transmission impedance, each phone can only transmit directly to two adjacent nodes. Because the nodes in this invention act as relays, when the audio duration per frame is 400ms, the bus experiences no strain when three phones are talking, and the measured audio loss time for one hour is 0. The verification results are shown in Figure 15.

[0121] During an audio call, the encoded audio frame actually contains many silence frames and comfort noise frames. Moreover, during a three-way call, there is no situation where each of the three parties speaks individually; there is always someone speaking and someone listening. Therefore, in order to further save carrier bandwidth resources, this invention also marks the silence frames and comfort noise frames during audio transmission, instead of transmitting the complete frames. At the receiving party, the frames are re-synthesized based on the markings, and the system performance is further optimized.

[0122] Any process or method description in the flowchart or otherwise herein can be understood as representing a module, segment, or portion of code comprising one or more executable instructions for implementing a particular logical function or process, and the scope of the preferred embodiments of the invention includes additional implementations in which functions may be performed not in the order shown or discussed, including substantially simultaneously or in reverse order depending on the functions involved, as will be understood by those skilled in the art to which embodiments of the invention pertain.

[0123] It should be understood that various parts of the present invention can be implemented using hardware, software, firmware, or a combination thereof. In the above embodiments, multiple steps or methods can be implemented using software or firmware stored in memory and executed by a suitable instruction execution device.

[0124] Those skilled in the art will understand that all or part of the steps of the methods in the above embodiments can be implemented by a program instructing related hardware. The program can be stored in a computer-readable storage medium, and when executed, the program includes one or a combination of the steps of the method embodiments.

[0125] The storage media mentioned above can be read-only memory, disk, or optical disk, etc.

[0126] In the description of this specification, references to terms such as "an embodiment," "some embodiments," "example," "specific example," or "embodiment," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0127] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

[0128] The long-distance carrier digital communication system of this invention has no central node, no exchange, low-voltage power supply, is hot-swappable, and is simple to install and maintain. The system does not specify wiring methods; it only needs to be connected to the power supply line to communicate, further simplifying installation and maintenance. The system can simultaneously connect to dozens of phones, meeting most application needs; it can achieve multi-party calls at the same time (limited to a maximum of three parties due to carrier bandwidth limitations); phones in any location can be interchanged, further simplifying installation and maintenance; the longest communication distance between phones can reach several kilometers; and during a call, any phone can simultaneously activate a broadcast, which can be received by all phones in the system; the system also includes a driver's phone, which can be inserted into a three-way call and can also activate a network-wide alarm.

[0129] In this specification, the invention has been described with reference to specific embodiments thereof. However, it will be apparent that various modifications and variations can be made without departing from the spirit and scope of the invention. Therefore, the specification and drawings should be considered illustrative rather than restrictive.

Claims

1. A long distance carrier digital messaging system, comprising: The system includes a low-voltage power supply and several digital telephones, both of which are connected to a carrier bus. Each digital telephone includes a power supply baseboard, an audio processing board, a carrier communication board, and telephone input / output accessories. The power supply baseboard, audio processing board, and carrier communication board are interconnected via interfaces. The power supply baseboard and carrier communication board communicate via serial port, and the communication content includes time, switch status, audio data, bus occupancy mode sent from the power supply baseboard to the carrier communication board, and local setting control mode returned from the carrier communication board to the power supply baseboard.

2. The long-distance carrier digital communication system according to claim 1, characterized in that, The system has a baseboard serial port receiving task designed for the application layer software of the carrier communication board, and the processing flow is as follows: (1.1) The carrier communication board receives the task and determines whether there is a data frame from the power supply base. If not, the step is repeated; otherwise, proceed to (1.2). (1.2) Determine whether the current data frame is an AT command frame. If it is, execute the corresponding AT command; otherwise, proceed directly to (1.3). (1.3) Determine again whether the data frame of the power supply base is included. If yes, cache the data of the power supply base. Otherwise, return to step (1.1).

3. The long-distance carrier digital communication system according to claim 1, characterized in that, The system described above has a carrier data reception task designed into the application layer software of the carrier communication board, and the processing flow is as follows: (2.1) Start the carrier reception task and determine whether there is a carrier frame. If not, repeat the step; otherwise, proceed directly to (2.2). (2.2) The process of extracting carrier data, controlling the transmission time, updating the data list, obtaining the bus occupancy mode of other machines, setting the local status and other machine table, forwarding carrier data, and sending the data of other machines to the power supply baseboard is executed in sequence to complete the reception of carrier data.

4. The long distance carrier digital messaging system of claim 1 wherein, The system described above has an application layer software design for the carrier communication board that includes a carrier active transmission task. The processing flow is as follows: (3.1) Start executing the carrier active transmission task, extract the current operating status of the digital telephone and generate the carrier occupancy control word; (3.2) Determine whether the carrier line needs to be occupied for task transmission. If not, perform short delay processing directly; otherwise, proceed to (3.3). (3.3) Determine whether the current corresponding task's transmission time has arrived. If so, perform carrier transmission processing and then perform short delay. Otherwise, perform short delay processing directly.

5. The long-distance carrier digital communication system according to claim 3, characterized in that, The carrier frames are generated and transmitted in the following manner: (2.1.1) The carrier transmission task for receiving instructions or data begins; (2.1.2) Set the address, identifier, and sending station address of the next station, and fill in the pass-through word and magic word; (2.1.3) Set the current frame as a downlink frame and set the data source address; (2.1.4) Fill the load with serial port buffer and calculate the cyclic redundancy check code (CRC), the load, and the number of frame bytes; (2.1.5) Carrier transmission: The carrier transmission task for the corresponding command or data ends.

6. The long-distance carrier digital communication system according to claim 3, characterized in that, When the carrier acquires a new frame, the transmission time point is calculated as follows: (2.2.1) Start calculating the transmission time point; (2.2.2) Sort the current data source list and calculate the sorted sequence number of the received frame data source; (2.2.3) Determine if the current data source sequence number is the largest. If it is, the reference at the current sending time point is the remainder of the system time % sending period. Otherwise, the current reference remains unchanged. (2.2.4) Calculate the sequence number after sorting on the local machine, and determine whether the current local sequence number is the largest. If it is, the sending time point = (base time + sequence number × time slice)% sending period; otherwise, the local sending time point is not adjusted. (2.2.5) The calculation of the sending time point ends.

7. The long-distance carrier digital communication system according to claim 3, characterized in that, Update the carrier data source list as follows; (2.3.1) Start updating the data source list; (2.3.2) Determine if the current data source address exists. If not, a new data source needs to be added; otherwise, proceed directly to (2.3.3). (2.3.3) Determine if the current identifier is new. If not, end the list update directly. Otherwise, proceed to (2.3.4). (2.3.4) Calculate the current identifier interval, where the number of missing audio frames is the difference between the old and new identifiers; (2.3.5) Determine if there is a missing frame. If so, calculate the missing audio time and accumulate the missing audio time. Otherwise, proceed directly to (2.3.6). (2.3.6) Determine if the current interval time is larger. If it is, replace the maximum identifier interval first. Otherwise, directly record the system time of the current identifier. (2.3.7) Set the remaining time for deleting the data source and end the data source list update.

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