A voice intercom extension board circuit

Abstract

The utility model discloses a speech intercom extension board mainboard circuit, including, main control and communication chip U1 adopt ML160T chip for realizing the control and communication function of equipment, VBAT main low voltage stabilish circuit is linked with main control and communication chip U1 for the output steady 3.82V is given main control and communication chip U1 power supply, low voltage stabilish circuit is linked with main control and communication chip U1 for providing 3.3V and 1.8V low voltage power supply for system stability, compared with existing duplex wireless intercom extension device, novel thing networking extension, use's 4G wireless communication module ML160T, has realized 4G network communication, because of its high degree of integration, make the circuit design simple, low power consumption, communication effect is more stable, not present distance. And can realize 485 protocol function, can butt joint different protocol, realizes the interactive butt joint between different equipment. This board can connect different compatible type's switching board board, compatible different brand's elevator limited intercom, guarantees product diversity matching.

Description

Technical Field

[0001] This utility model relates to the field of voice intercom extension technology, specifically a voice intercom extension motherboard circuit. Background Technology

[0002] In the current communications field, voice intercom extensions are key devices in scenarios such as security monitoring, elevator communication, and industrial control. However, traditional voice intercom extensions generally use FM (Frequency Modulation) for communication. This technical solution has many unavoidable limitations in practical applications and is gradually failing to meet the high communication quality requirements of modern scenarios.

[0003] Traditional FM walkie-talkies rely on the straight-line propagation characteristics of radio waves, making them highly susceptible to the effects of ground obstacles. In complex environments such as dense urban buildings, underground parking lots, mines, or large industrial parks, radio waves are easily blocked, reflected, or absorbed, resulting in a significant reduction in effective communication distance, typically covering only 3-5 kilometers at most.

[0004] Furthermore, traditional FM walkie-talkies typically require high-power transmitter modules to ensure limited communication distance and signal strength, resulting in high power consumption. For battery-powered mobile walkie-talkies, high power consumption means frequent charging or battery replacement, increasing maintenance costs and inconvenience.

[0005] To address this, a voice intercom extension motherboard circuit is proposed. Summary of the Invention

[0006] The purpose of this utility model is to provide a voice intercom extension motherboard circuit to solve the problems mentioned in the background art.

[0007] To achieve the above objectives, this utility model provides the following technical solution: a voice intercom extension motherboard circuit, comprising:

[0008] The main control and communication chip U1 uses the ML160T chip to realize the control and communication functions of the device;

[0009] The VBAT main low-voltage regulator circuit is connected to the main control and communication chip U1 and is used to output a stable 3.82V to power the main control and communication chip U1.

[0010] The low-voltage regulator circuit is connected to the main control and communication chip U1 and is used to provide a stable 3.3V and 1.8V low-voltage power supply for the system.

[0011] The 485 communication circuit is connected to the main controller and communication chip U1 and is used for communication and data linkage with other external devices.

[0012] The SIM card reading circuit is connected to the main control and communication chip U1 and is used to read and interact with data from the SIM card or USIM card.

[0013] The software programming circuit is connected to the main control and communication chip U1 and is used to realize the connection and data transmission between the device and the external USB device, and to program the relevant software program into the main control and communication chip U1.

[0014] The audio signal input circuit is connected to the main control and communication chip U1. It is used to process the audio signal and transmit it to the main control and communication chip U1 so that the signal can be transmitted to the signal receiving terminal through the antenna.

[0015] The audio signal receiving and processing circuit is connected to the main control and communication chip U1, and is used to process and transmit audio signals. It is connected to the audio output device of the switching board.

[0016] The power indicator circuit is connected to the main control and communication chip U1 and is used to indicate whether the power supply and network access are normal.

[0017] The four-way switch control circuit is connected to the main control and communication chip U1 and is used to control the switching board circuit through control signals.

[0018] The four dial-up conversion circuits on the switching board are connected to the main control and communication chip U1. They are used to process the input signals to meet the needs of subsequent circuits and perform level conversion.

[0019] The network port circuit, connected to the main control and communication chip U1, is used to realize the Ethernet communication function of the device, ensuring that data can be transmitted stably and reliably between the device and the network.

[0020] Preferably, the 46th pin of the main control and communication chip U1 is connected to a capacitor C7 and a resistor R10, and a capacitor C8, a bidirectional diode D2 and an antenna ANT are connected to the resistor R10.

[0021] The VBAT main low-voltage regulator circuit includes a chip U4. A capacitor C52 is connected between pins 2 and 6 of the chip U4. One end of an inductor L1 is also connected to pin 2 of the chip U4. The other end of the inductor L1 is connected to capacitors C48, C49, C51, resistors R67 and R68. A capacitor C47, C46, ​​and C50 are connected to pin 3 of the chip U4. A resistor R1 and a resistor R2 are connected to pin 5 of the chip U4.

[0022] The low-voltage regulator circuit includes chip U5 and chip U6. Capacitors C56 and C55 are connected between pins 1 and 2 of chip U5. Pin 5 of chip U5 is connected to pin 1 of chip U6. Capacitors C59, C58 and C57 are connected between pins 1 and 2 of chip U6. Capacitors C54 and C53 are connected to pin 5 of chip U6.

[0023] Preferably, the 485 communication circuit includes a chip U3 and a terminal block P3. Pin 1 of the chip U3 is connected to resistors R46 and R44 and is connected to pins 31 and 67 of the main control and communication chip U1. Pins 2 and 3 of the chip U3 are connected to resistor R30. Pin 4 of the chip U3 is connected to resistor R49 and is connected to pin 32 of the main control and communication chip U1. Pin 6 of the chip U3 is connected to resistors R55 and R50 and is connected to pin 1 of the terminal block P3. Pin 7 of the chip U3 is connected to resistor R47 and is connected to pin 2 of the terminal block P3. Pin 8 of the chip U3 is connected to capacitor C31 and is connected to pin 3 of the terminal block P3. Resistor R42 and capacitor C34 are connected between pins 7 and 8 of the chip U3. Resistor R81 is connected between pins 6 and 7 of the chip U3.

[0024] The SIM card reading circuit includes a self-ejecting SIM card slot SIM1. Pin 1 of the SIM card slot SIM1 is connected to a diode D4, a capacitor C9, and a resistor R11 and is connected to pin 8 of the main control and communication chip U1. The resistor R11 is connected to pin 6 of the SIM card slot SIM1. Pin 3 of the SIM card slot SIM1 is connected to a diode D3, a capacitor C11, and a resistor R13 and is connected to pin 7 of the main control and communication chip U1. Pin 5 of the SIM card slot SIM1 is connected to a diode D6, a capacitor C12, and a resistor R14 and is connected to pin 5 of the main control and communication chip U1. Pin 6 of the SIM card slot SIM1 is connected to a diode D5, a capacitor C13, and a resistor R15 and is connected to pin 6 of the main control and communication chip U1.

[0025] Preferably, the software programming circuit includes a TYPE-C interface J1, pins A4 and A9 of the TYPE-C interface J1 are connected, pin A9 of the TYPE-C interface J1 is connected to a diode D12 and a capacitor C25 and is connected to pin 28 of the main control and communication chip U1, pin A5 of the TYPE-C interface J1 is connected to a resistor R22, pin A6 of the TYPE-C interface J1 is connected to a diode D10 and is connected to pin 26 of the main control and communication chip U1, and pin A7 of the TYPE-C interface J1 is connected to a diode D11 and is connected to pin 27 of the main control and communication chip U1.

[0026] Pins B4 and B9 of the TYPE-C interface J1 are connected to pin 28 of the main control and communication chip U1. Pin B5 of the TYPE-C interface J1 is connected to resistor R29. Pins B6 and B7 of the TYPE-C interface J1 are connected to pins 26 and 27 of the main control and communication chip U1, respectively.

[0027] Preferably, the audio signal input circuit includes resistors R23 and R31. One end of resistors R23 and R31 is connected to pins 24 and 23 of the main control and communication chip U1, respectively. The other end of resistors R23 and R31 is connected to capacitors C17, C18, C16, C21, C22, C20, C24, and C23. One end of resistor R19 and capacitor C19 are connected between capacitors C16 and C20. The other end of resistor R19 is connected to pin 25 of the main control and communication chip U1. Resistors R32 and R28 are connected between capacitors C20 and C23. The other end of resistor R32 is connected to diode D9 and to pin 3 of terminal P2.

[0028] The audio signal receiving and processing circuit includes resistors R39 and R35. One end of resistors R39 and R35 is connected to pins 21 and 22 of the main control and communication chip U1, respectively. The other end of resistor R39 is connected to capacitor C29. The other end of resistor R35 is connected to capacitors C27 and C28, diode D8, and resistor R21. The other ends of diode D8 and resistor R21 are connected to pin 4 of terminal P2.

[0029] Preferably, the power indicator circuit includes two light-emitting diodes (LEDs) LED1. One end of one LED LED1 is connected to a resistor R9, and one end of the other LED LED1 is connected to one end of a resistor R3. The other end of the resistor R3 is connected to the collector of a transistor Q1. The base of the transistor Q1 is connected to a resistor R4 and is connected to pin 69 of the main control and communication chip U1. A resistor R6 is connected between the base and emitter of the transistor Q1.

[0030] Preferably, the four-way switch control circuit includes transistors Q11, Q12, Q13, and Q14;

[0031] The base of transistor Q11 is connected to one end of resistor R48 and resistor R61. The other end of resistor R48 is connected to pin 16 of the main control and communication chip U1. The collector of transistor Q11 is connected to one end of resistor R37. The other end of resistor R37 is connected to the base of transistor Q7. Resistor R8 is connected between the emitter and base of transistor Q7. The collector of transistor Q7 is connected to pin 5 of terminal P2.

[0032] The base of transistor Q12 is connected to one end of resistor R51 and resistor R79. The other end of resistor R51 is connected to pin 14 of the main control and communication chip U1. The collector of transistor Q12 is connected to one end of resistor R38. The other end of resistor R38 is connected to the base of transistor Q8. Resistor R12 is connected between the emitter and base of transistor Q8. The collector of transistor Q8 is connected to pin 7 of terminal P2.

[0033] The base of transistor Q13 is connected to one end of resistor R52 and resistor R27. The other end of resistor R52 is connected to pin 12 of the main control and communication chip U1. The collector of transistor Q13 is connected to one end of resistor R43. The other end of resistor R43 is connected to the base of transistor Q9. Resistor R25 is connected between the emitter and base of transistor Q9. The collector of transistor Q9 is connected to pin 9 of terminal P2.

[0034] The base of transistor Q14 is connected to one end of resistor R60 and resistor R80. The other end of resistor R60 is connected to pin 10 of the main control and communication chip U1. The collector of transistor Q14 is connected to one end of resistor R45. The other end of resistor R45 is connected to the base of transistor Q10. Resistor R36 is connected between the emitter and base of transistor Q10. The collector of transistor Q10 is connected to pin 11 of terminal P2.

[0035] Preferably, the four dial-up switching circuits on the switching board include transistors Q2, Q3, Q4, and Q5;

[0036] The base of transistor Q2 is connected to resistor R5 and is connected to pin 10 of terminal P2. Resistor R64 is connected between the emitter and base of transistor Q2. One end of resistor R57 is connected to the collector of transistor Q2 and is connected to pin 11 of main control and communication chip U1. The other end of resistor R57 is connected to pin 76 of main control and communication chip U1.

[0037] The base of transistor Q3 is connected to resistor R7 and is connected to pin 12 of terminal P2. Resistor R65 is connected between the emitter and base of transistor Q3. One end of resistor R58 is connected to the collector of transistor Q3 and is connected to pin 9 of main control and communication chip U1. The other end of resistor R58 is connected to pin 76 of main control and communication chip U1.

[0038] The base of transistor Q4 is connected to resistor R18 and is connected to pin 6 of terminal P2. Resistor R40 is connected between the emitter and base of transistor Q4. One end of resistor R33 is connected to the collector of transistor Q4 and is connected to pin 15 of main control and communication chip U1. The other end of resistor R33 is connected to pin 76 of main control and communication chip U1.

[0039] The base of transistor Q5 is connected to resistor R26 and is connected to pin 8 of terminal P2. Resistor R41 is connected between the emitter and base of transistor Q5. One end of resistor R34 is connected to the collector of transistor Q5 and is connected to pin 13 of main control and communication chip U1. The other end of resistor R34 is connected to pin 76 of main control and communication chip U1.

[0040] Preferably, the network port circuit includes a main control chip U7. A resistor R75 and a crystal oscillator Y1 are connected between pins 10 and 11 of the main control chip U7. Pins 4, 5, 7, and 8 of the main control chip U7 are respectively connected to pins 3, 6, 1, and 2 of the network port transformer HR911105A. One end of resistor R71, one end of resistor R72, one end of resistor R73, and one end of resistor R74 are connected between pins 4 and 5 of the network port transformer HR911105A. The other end of resistor R71 is connected to pin 1 of the network transformer HR911105A. The other end of resistor R72 is connected to pin 2 of the network transformer HR911105A. The other end of resistor R73 is connected to pin 6 of the network transformer HR911105A. The other end of resistor R74 is connected to pin 3 of the network transformer HR911105A. Resistors R76 and R77 are connected to pins 9 and 12 of the network transformer HR911105A, respectively.

[0041] Compared with existing technologies, the beneficial effects of this utility model are as follows: Compared with existing full-duplex wireless intercom extension devices, the new IoT extension uses the ML160T 4G wireless communication module, which realizes 4G network communication. Due to its high integration, the circuit design is simple, power consumption is low, and the communication effect is more stable regardless of distance. Furthermore, it can implement the 485 protocol function, allowing it to interface with different protocols and achieve interactive interfacing between different devices. This board can connect to different compatible types of switching boards, thus being compatible with different brands of elevator wired intercoms, ensuring diverse product compatibility. Attached Figure Description

[0042] Figure 1 This is a schematic diagram of the main control and communication chip U1 of this utility model;

[0043] Figure 2 This is a schematic diagram of the VBAT main low-voltage regulator circuit of this utility model;

[0044] Figure 3 This is a schematic diagram of the low-voltage regulator circuit of this utility model;

[0045] Figure 4 This is a schematic diagram of the 485 communication circuit of this utility model;

[0046] Figure 5 This is a schematic diagram of the mobile phone card reading circuit of this utility model;

[0047] Figure 6 This is a schematic diagram of the software programming circuit of this utility model;

[0048] Figure 7 This is a schematic diagram of the audio signal input circuit of this utility model;

[0049] Figure 8 This is a schematic diagram of the audio signal receiving and processing circuit of this utility model;

[0050] Figure 9 This is a schematic diagram of the power indicator circuit of this utility model;

[0051] Figure 10 This is a schematic diagram of the four-way switch control circuit of this utility model;

[0052] Figure 11 This is a schematic diagram of the four dial-up switching circuits on the switching board of this utility model;

[0053] Figure 12 This is a schematic diagram of the network port circuit of this utility model. Detailed Implementation

[0054] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention.

[0055] Please see Figure 1-12 This utility model provides a technical solution:

[0056] The main control and communication chip U1, such as Figure 1 As shown, this product is developed using the ML160T 4G wireless communication module platform from Qijun IoT Co., Ltd. This module is in LCC+LGA package, supports LTE-TDD / LTE-FDD standards, and integrates data transmission, voice services, value-added services, power management, and other functions, serving as the main control and communication unit. Two sets of filtering and anti-interference circuits are added to the front end of the power supply pins: large-capacity electrolytic capacitors C6 and C5 for low-frequency filtering and power stabilization; surface-mount capacitors C1 and C3 for high-frequency decoupling and noise suppression; and small-capacity capacitors C2 and C4 for high-frequency noise absorption and EMI suppression. A bidirectional suppression diode D1 with a voltage limit of 5V is also added.

[0057] VBAT main low-voltage regulator circuit, such as Figure 2 As shown, the H9118-ADJ adjustable output linear regulator chip U4, through the voltage divider feedback of R67 and R68, adjusts the input VCC12V and its related circuitry, combined with three filter capacitors C48, C49, and C51, to achieve a stable output VBAT (3.82V) to power the communication module U1. A stepped filter is constructed using 470μF, 1μF, and 100nF capacitors to cover noise across the entire frequency band, ensuring a clean 12V output. The 12V is then reduced to VBAT (3.82V). An LC filter and capacitors form a π-type filter to further smooth the voltage.

[0058] C51 (470μF) and C50 (470μF) are high-capacity electrolytic capacitors used for low-frequency filtering, stabilizing the 12V power supply, and handling large current fluctuations. C49 (1μF) and C46 (1μF) are intermediate-frequency decoupling capacitors, filtering out medium-frequency noise. C48 (100nF) and C47 (100nF) are high-frequency capacitors, used for high-frequency decoupling, suppressing fast transient interference.

[0059] Low-voltage regulator circuits, such as Figure 3 As shown, this is a two-stage buck regulator circuit based on the ME6211 series linear regulator. It sequentially steps down the input voltage to 3.3V (VCC_33) and 1.8V (VCC_1V8) to provide a stable low-voltage power supply for the system. The ME6211 is a low-dropout linear regulator that uses a linear adjustment transistor to achieve voltage reduction and regulation, with a fixed output voltage. U5 outputs 3.3V, and U6 outputs 1.8V. It features a simple structure, low noise, and is suitable for applications requiring high power purity.

[0060] The circuit employs a two-stage step-down converter. The first stage uses VBAT and 3.3V (U5: ME6211C33M5G-N). VBAT is the input voltage, which is filtered by C55 and C56 before being sent to the VIN pin of U5. Internally, U5 uses a linear regulator to step down the input voltage to 3.3V, which is then output from VOUT. The EN pin is enabled by default at a high level. C57, C58, and C59 further filter the voltage to ensure a stable 3.3V output.

[0061] Second stage: 3.3V, 1.8V (U6: ME6211C18M5G-N). The 3.3V (VCC_33) output from U5 serves as the input to U6, entering through the VIN pin. U6 internally linearly adjusts the voltage, stepping down the 3.3V to 1.8V, which is then output from VOUT (VCC_1V8). A high level on the EN pin enables the output, and filters C53 and C54 ensure a clean 1.8V output.

[0062] The ME6211 chips U5 and U6 regulate the voltage drop of the linear regulator transistor through internal feedback to stabilize the output voltage. Input filter capacitors C55, C56, C57, C58, and C59 filter out input voltage ripple; a large capacitor C55 is used for low frequencies, and a small capacitor C56 is used for high frequencies to ensure stable LDO operation. Output filter capacitors C57, C58, C59, C53, and C54 filter out LDO output ripple, further purifying the power supply and providing clean voltage to downstream loads.

[0063] 485 communication circuit, such as Figure 4 As shown, the SIT3088EESA(U3), a half-duplex RS-485 / RS-422 differential bus transceiver manufactured by Silicon Integration Tech, enables this product to communicate and link with other external devices via terminal P3. Chip U3 performs TTL-to-RS-485 level conversion, allowing the microcontroller to communicate with an external 485 bus via a TTL level interface. VCC_33 provides 3.3V power to the chip and some circuitry. Pin 8 of chip U3 is connected to VCC_33 for power supply, ensuring normal chip operation. Capacitor C31 filters high-frequency noise from the power supply, making the VCC_33 power supply more stable and improving the circuit's anti-interference capability. Resistors R30 and R44 form a voltage divider circuit for level matching of the RX signal, while R46 limits current to protect the chip's receive pin RO. R49 is a current-limiting resistor for the TX signal, protecting the chip's transmit pin DI. The TX and RX pins are connected to the microcontroller's transmit and receive pins, enabling TTL level signal transmission between the microcontroller and the 485 chip. Pins A1 and B1 are used to connect to an external RS485 bus. Resistors R42 and R55 ensure a defined voltage level on the RS485 bus in idle mode, enhancing communication stability and preventing signal interference and bit errors. Resistors R47 and R50 provide impedance matching, reducing signal reflection and improving signal transmission quality. Capacitors C34 and C41 filter out high-frequency interference signals on the bus, improving signal quality. Interface P3 (XH-3AW) is used to connect external RS485 bus devices, establishing the physical connection between the circuit and external devices.

[0064] The microcontroller sends TTL level data to the DI pin of the 485 chip via the TX pin. The chip converts the TTL level to 485 level and outputs it from the A1 and B1 pins to the 485 bus for transmission to other 485 devices. Data sent by external 485 devices arrives at the A1 and B1 pins via the 485 bus. The 485 chip converts it to TTL level, outputs it from the RO pin, and transmits it to the microcontroller via the RX pin.

[0065] SIM card reader circuit, such as Figure 5As shown, a 6-pin self-ejecting SIM card slot is used to read and interact with data from the SIM card or USIM card. Communication with the 4G module is achieved through three resistors R13, R14, and R15, using a dedicated 1.8V voltage provided by the module, and a filter capacitor C9 is added. The circuit design includes four transient suppression diodes D3-D6 to prevent static electricity and interference brought in from the card slot, protecting the 4G module. Additional filter capacitors C11, C12, and C13 further filter out noise interference signals.

[0066] The 6-pin SIM card interface on SIM1 is used to insert a SIM card or USIM card for physical connection. Capacitor C9 is connected between USIMVDD and GND to filter out high-frequency noise in the power supply, making the SIM card power supply more stable. Resistor R11 ensures a stable pin level for USIMVDD. Resistors R13-R15 are connected in series on the USIMRST, USIMCLK, and USIMDATA signal lines respectively, serving to limit current, match impedance, protect the circuit, and improve signal transmission stability. Capacitors C11-C13 filter out high-frequency interference on the RST, CLK, and DATA signal lines, improving signal quality. Diodes D3-D6 provide ESD (electrostatic discharge) protection, preventing damage to the SIM card interface circuit from transient high voltages such as static electricity.

[0067] The power supply provides a stable operating voltage to the SIM card through the VCC pin (after filtering via C9, etc.), enabling the SIM card to enter a working state. When the system needs to reset the SIM card, a reset signal is sent through the RST pin to initialize the SIM card. The CLK pin provides a clock signal to the SIM card, ensuring timing synchronization between the SIM card and external circuits in data transmission and other operations. Data interaction with the SIM card is achieved through I / O pins, such as reading information stored on the card and writing commands. Simultaneously, protection and filtering components in the circuit work together to ensure stable and reliable signal transmission, preventing damage to the circuit and SIM card from external interference and static electricity.

[0068] Software programming circuits, such as Figure 6As shown, this is a Type-C interface circuit used to connect and transmit data between the device and an external USB device. The relevant software is burned into the main control communication module U1 to achieve the corresponding functions. The Type-C interface offers advantages such as convenient reversible insertion and support for high-speed data transmission. The Type-C interface J1, as the physical connection port, has multiple pins for power supply, data transmission, and other functions. Pins A4, A9, B4, and B5 are power transmission pins used to transmit power and support different charging voltages and current levels. Pins A6 and B7, and A7 and B6 are differential data transmission pins used for high-speed data transmission, conforming to the USB protocol specification. Pins A5 and B8 are configuration channel pins used to detect the type of connected device, negotiate power supply capability, and data transmission mode. Pins A8 and B9 are auxiliary signal pins that can be used to transmit non-USB standard signals, such as audio signals.

[0069] Capacitor C25 is connected between VBUS and GND, acting as a power filter to remove high-frequency noise from the VBUS power line, making the power supply more stable. Resistors R22 and R29 are connected in series on the USBDP and USBDM signal lines respectively, serving as impedance matching devices to reduce signal reflections, improve the stability and reliability of data transmission, and meet the impedance requirements of USB signal transmission. Diodes D10-D12 provide ESD (electrostatic discharge) protection, preventing damage to the USB interface circuitry from transient high voltages such as static electricity, and protecting internal circuit components.

[0070] When an external device (such as a charger) is connected via the TYPE-C interface, the VBUS pin transmits power to charge the device or power internal circuitry. C25 filters the VBUS power supply to ensure power quality. The USBDP and USBDM pins transmit data in differential signal form, and R22 and R29 ensure impedance matching during signal transmission. The device communicates via the CC1 and CC2 pins to negotiate parameters such as data transfer rate and power supply capability. In the event of transient high voltages such as electrostatic discharge, D10-D12 conduct, diverting the excessive voltage to ground to prevent damage to the interface and internal circuitry, thus ensuring circuit stability and reliability.

[0071] Audio signal input circuit, such as Figure 7As shown, this is an audio signal input circuit. Its main function is to process the audio signal and transmit it to the 4G wireless communication module ML160T(U1) so that the signal can be transmitted to the signal receiving terminal through the antenna. R23 and R31 are connected in series on the MIC_P and MIC_N signal lines respectively, and R32 is at the TX_A output terminal. They limit the current in the circuit and prevent excessive current from damaging subsequent circuit components, thus providing overcurrent protection. C17 is connected between MIC_P and the subsequent circuit, C21 is connected between MIC_N and the subsequent circuit, and C19 is in the signal transmission path. Its function is to couple the audio AC signal through its AC-passing and DC-blocking characteristics, and isolate the DC component to ensure normal signal transmission. Filter capacitors C18, C16, C23, and C24 are connected in parallel on the signal lines to filter out high-frequency noise and other interference components in the audio signal, making the transmitted audio signal cleaner. C20 and C22, together with R19 and R28, form a feedback loop. By introducing appropriate negative feedback and adjusting the circuit gain, self-oscillation during signal amplification is prevented, thus avoiding howling and ensuring the stability of audio signal processing. Diode D9 provides ESD (electrostatic discharge) protection, preventing damage to the circuit from transient high voltages such as static electricity, and protecting subsequent connected components such as the 4G wireless communication module.

[0072] The switching board outputs a signal to this circuit via the P2TX_A interface. After passing through the electrostatic discharge protection circuit D9, the signal's gain is adjusted by the feedback circuit composed of R19, R28, C20, and C22. C18, C16, C23, and C24 then filter the signal to remove high-frequency interference. After current limiting by R23 and R31, the audio signal is output from MIC_P and MIC_N and transmitted to the corresponding ports of the ML160T 4G wireless communication module, ultimately being sent to the signal receiving terminal via the antenna.

[0073] Audio signal receiving and processing circuit, such as Figure 8As shown, this circuit is an audio signal output circuit, mainly used to process and transmit audio signals, connecting to the audio output device on the switching board. Resistors R35 and R39 are 0-ohm resistors, mainly serving as connecting wires in the circuit, facilitating debugging and layout. They can be used to connect the audio signal sources (SPK_P and SPK_N) to subsequent circuits, and can also be replaced with resistors with resistance values ​​to adjust signal strength, etc., as needed. C27 and C28 are high-frequency bypass capacitors, connected in parallel on the SPK_P signal line, used to filter out high-frequency noise in the SPK_P signal, making the audio signal cleaner. C29 is a coupling capacitor, connected on the SPK_N signal line, utilizing its AC-passing and DC-blocking characteristics to couple and transmit the audio AC signal, isolating the DC component and ensuring the normal transmission of the audio signal to subsequent circuits. Diode D8 provides ESD (electrostatic discharge) protection, preventing damage to the circuit from transient high voltages such as static electricity, protecting subsequently connected equipment or circuit components. Resistor R21 pulls the RX_A signal pin low to ensure that the pin is in a stable low level when there is no signal input, preventing signal interference and false triggering.

[0074] The audio signal is input from SPK_P and SPK_N. The SPK_P signal first passes through R35, and high-frequency noise is filtered out by C27 and C28. The SPK_N signal passes through R39 and is coupled by C29. The processed signals converge at node RX_A. D8 provides electrostatic protection for this node, and R21 maintains a stable level on the RX_A pin. The final processed audio signal is output from RX_A and can be connected to an audio receiving device for further processing or playback.

[0075] Power indicator circuit, such as Figure 9 As shown, this is an LED driver circuit, mainly used to control the lighting and extinguishing of LEDs and to indicate whether the power supply and grid connection are normal. The LED serves as an indicator. R3 is connected in series in the LED1 branch to limit the current flowing through LED1, preventing excessive current from damaging it. R4 is connected in series in the LED-R branch to limit excessive current and prevent damage to LED1. R5 is connected to the base of transistor Q1 to control the base current, thereby controlling the transistor's conduction level. Transistor Q1 is an NPN transistor, acting as a switch or current amplifier here. By controlling the base current, the conduction and cutoff between the collector and emitter can be achieved, thus controlling the lighting and extinguishing of LED-R.

[0076] Four-way switch control circuit, such as Figure 10As shown, this part of the circuit consists of four sets of switch control circuits corresponding to channels 1-4, which control the corresponding circuits of groups 1-4 on the switching board via the P2 connector. The first group is listed for illustration; the other groups 2-4 are similar and will not be elaborated further. The product uses a transistor-based switch control circuit, mainly used to control the on / off state of the switching board circuits via a control signal (SW1). Q7 is a PNP transistor, which can act as an electronic switch in the circuit. When the base voltage is appropriate, it can conduct, forming a path between VBAT and SW1, supplying power or transmitting signals to subsequent circuits. Q11 is an NPN transistor, used to control the base potential of Q7. By controlling the conduction and cutoff of Q11, the operating state of Q7 is indirectly controlled. R8 is connected between VBAT and the base of Q7, serving as a current limiter and bias, providing a suitable bias voltage to the base of Q7. R37 is connected in series between the emitter of Q7 and the collector of Q11, used to limit the current and also participate in the adjustment of the base potential of Q7. R48 is connected between SW1_M and the base of Q11, serving as a current limiter and signal regulator to control the base current of Q11. R61 is a base pull-down resistor for Q11, pulling the base of Q11 low to ensure that Q11 is cut off when there is no input signal, thus guaranteeing circuit stability.

[0077] When the SW1_M input is high, current flows through R48 into the base of Q11, turning Q11 on. After Q11 turns on, its collector potential rises, which in turn lowers the base potential of Q7 through R37. Since Q7 is a PNP transistor, the decrease in its base potential turns it on, thus creating a path between VBAT and SW1, enabling the circuit to conduct and providing a high level to the load connected to SW1.

[0078] When the SW1_M input is low, the base potential of Q11 is low, and Q11 is cut off. After Q11 is cut off, the base potential of Q7 rises, and Q7 is also cut off. The circuit between VBAT and SW1 is broken, and the output of low level to the load stops.

[0079] The four-way dial-up switching circuit on the switching board, such as... Figure 11 As shown, when the switching board provides the corresponding group dialing request signal, the product implements a processing and conversion circuit. Taking group 1 as an example, the same applies to groups 2-4. When group 1 of the switching board sends a dialing request signal, the CALL1 terminal on P2 changes from a 0V low level to a 5V high level. The transistor-based signal drive or level conversion circuit is mainly used to process the input signal (CALL1) to meet the needs of subsequent circuits (the part connected to CALL1_M) by performing level conversion.

[0080] Transistor Q4 is an NPN transistor, acting as a switch or signal amplifier in the circuit. By controlling the base current, the conduction and cutoff between the collector and emitter can be achieved, thereby controlling the voltage level of the CALL1_M node. Resistor R18 is a 0-ohm resistor, mainly used for connection, facilitating circuit debugging and layout, and allowing the CALL1 signal to be connected to the base of Q4. In some cases, it can be replaced with a resistor with a fixed value to adjust the signal strength, etc. Resistor R33 is a pull-up resistor, connected between VDD18_EXT and CALL1_M. When Q4 is off, it pulls the CALL1_M pin high to the VDD18_EXT level, ensuring that the pin is in a stable high-level state and preventing signal interference and false triggering. Resistor R40 is marked as NC and not connected in the diagram. If needed later, it can be connected to the circuit to serve as a base bias or current limiter, used to adjust the operating state of Q4.

[0081] When CALL1 input is high, current flows through R18 into the base of Q4, turning Q4 on. With Q4 on, the collector and emitter are approximately short-circuited, pulling the CALL1_M node potential low, close to ground (low level). When CALL1 input is low, the base current of Q4 is very small, and Q4 is off. At this time, due to the pull-up effect of R33, the CALL1_M node potential is pulled high to VDD18_EXT (high level). In this way, the level state of the CALL1_M node is controlled, providing the corresponding signal level to the switching board circuit.

[0082] Network port circuit, such as Figure 12 As shown, this circuit diagram involves Ethernet communication and includes key components such as power filtering, network port transformer, and main control chip.

[0083] In the power supply filtering section, the VCC_33 and VCC_1V8 power supply filter capacitor banks are shown in the diagram, with multiple sets of capacitors connected in parallel on the VCC_33 and VCC_1V8 power lines. For example, there are multiple 100N and 10U capacitors on the VCC_33 line, and a similar combination of capacitors on the VCC_1V8 line. These capacitors act as filters, removing high-frequency and low-frequency ripple from the power supply, providing a stable and clean power supply for subsequent circuits. Large-capacity capacitors filter out low-frequency ripple, while small-capacity capacitors filter out high-frequency noise, ensuring that chips and other components operate in a stable power supply environment and preventing power fluctuations from interfering with network communication.

[0084] The HR911105A Ethernet port transformer is a key component of the Ethernet port circuit, used to couple and electrically isolate Ethernet signals. It couples the Ethernet signals (TX and RX) of the main control chip to the RJ45 interface of the network port, while isolating the external network from the internal circuitry. This prevents external electrical interference and surges from affecting the internal circuitry and protects the main control chip. The primary coil of the transformer is connected to the main control chip, and the secondary coil is connected to the RJ45 interface, achieving signal transmission through electromagnetic induction. In terms of electrical isolation, the transformer can block the DC path between the external network and the internal circuitry, preventing damage to internal circuit components due to abnormal conditions such as high voltage and high current from the external network.

[0085] The HR911105A also drives the network port status indicator lights, controlling their on / off state via internal circuitry to provide users with intuitive feedback on network connection and data transmission status. When the network connection is normal and data is being transmitted, the control circuitry inside the transformer will cause the corresponding indicator light pin to output an appropriate level, driving the indicator light to illuminate.

[0086] The CH595Q is the main control chip responsible for processing Ethernet data. It communicates with other modules via interfaces such as SPI and UART, and connects to a network adapter via an Ethernet interface to transmit and receive data. When transmitting data, it converts the internally processed data into an Ethernet format signal and sends it to the network through the adapter. When receiving data, it receives the Ethernet signal transmitted from the adapter, parses and processes it. The chip integrates Ethernet MAC (Media Access Control) layer and PHY (Physical Layer) related circuitry. The MAC layer handles Ethernet data frame encapsulation and decapsulation, as well as media access control functions; the PHY layer converts the data from the MAC layer into signals suitable for transmission over the Ethernet physical link, and performs signal reception and preliminary processing.

[0087] Y1 is a 30MHz crystal oscillator that provides the operating clock for the CH595Q, ensuring that the internal circuitry of the chip operates according to precise timing. The reset circuit (such as the RST pin-related circuitry) is used to reset the chip to its initial state during system startup or in the event of an anomaly, ensuring normal chip operation. The clock signal generated by the crystal oscillator is processed by the chip's internal clock circuitry through frequency division and multiplication to provide the required clock frequency for each module. Upon receiving a reset signal (such as active low), the reset circuit resets the chip's internal registers, state machine, etc., causing the chip to start operating from its initial state.

[0088] The main control chip CH595Q encapsulates and processes the data to be sent, and then sends differential signals (TX1_P / TX1_N, etc.) to the network transformer (HR911105A) through the Ethernet interface. After the transformer couples and isolates the signals, they are sent to the external network through the RJ45 interface.

[0089] Data from the external network enters the Ethernet transformer via the RJ45 interface. The transformer couples the signal to the Ethernet interface of the main control chip. The main control chip processes the received data through decapsulation and parsing, and then transmits it to other modules for further processing via appropriate interfaces (such as SPI, UART, etc.). The Ethernet transformer drives the Ethernet indicator light based on the network connection and data transmission status, providing users with intuitive feedback on the network situation.

[0090] Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the present invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A voice intercom extension motherboard circuit, characterized in that, include: The main control and communication chip U1 uses the ML160T chip to realize the control and communication functions of the device; The VBAT main low-voltage regulator circuit is connected to the main control and communication chip U1 and is used to output a stable 3.82V to power the main control and communication chip U1. The low-voltage regulator circuit is connected to the main control and communication chip U1 and is used to provide a stable 3.3V and 1.8V low-voltage power supply for the system. The 485 communication circuit is connected to the main controller and communication chip U1 and is used for communication and data linkage with other external devices. The SIM card reading circuit is connected to the main control and communication chip U1 and is used to read and interact with data from the SIM card or USIM card. The software programming circuit is connected to the main control and communication chip U1 and is used to realize the connection and data transmission between the device and the external USB device, and to program the relevant software program into the main control and communication chip U1. The audio signal input circuit is connected to the main control and communication chip U1. It is used to process the audio signal and transmit it to the main control and communication chip U1 so that the signal can be transmitted to the signal receiving terminal through the antenna. The audio signal receiving and processing circuit is connected to the main control and communication chip U1, and is used to process and transmit audio signals. It is connected to the audio output device of the switching board. The power indicator circuit is connected to the main control and communication chip U1 and is used to indicate whether the power supply and network access are normal. The four-way switch control circuit is connected to the main control and communication chip U1 and is used to control the switching board circuit through control signals. The four dial-up conversion circuits on the switching board are connected to the main control and communication chip U1. They are used to process the input signals to meet the needs of subsequent circuits and perform level conversion. The network port circuit, connected to the main control and communication chip U1, is used to realize the Ethernet communication function of the device, ensuring that data can be transmitted stably and reliably between the device and the network.

2. The mainboard circuit for a voice intercom extension according to claim 1, characterized in that: The main control and communication chip U1 has a capacitor C7 and a resistor R10 connected to pin 46. A capacitor C8, a bidirectional diode D2 and an antenna ANT are connected to the resistor R10. The VBAT main low-voltage regulator circuit includes a chip U4. A capacitor C52 is connected between pins 2 and 6 of the chip U4. One end of an inductor L1 is also connected to pin 2 of the chip U4. The other end of the inductor L1 is connected to capacitors C48, C49, C51, resistors R67 and R68. A capacitor C47, C46, ​​and C50 are connected to pin 3 of the chip U4. A resistor R1 and a resistor R2 are connected to pin 5 of the chip U4. The low-voltage regulator circuit includes chip U5 and chip U6. Capacitors C56 and C55 are connected between pins 1 and 2 of chip U5. Pin 5 of chip U5 is connected to pin 1 of chip U6. Capacitors C59, C58 and C57 are connected between pins 1 and 2 of chip U6. Capacitors C54 and C53 are connected to pin 5 of chip U6.

3. The mainboard circuit for a voice intercom extension according to claim 1, characterized in that: The 485 communication circuit includes chip U3 and terminal P3. Pin 1 of chip U3 is connected to resistors R46 and R44 and is connected to pins 31 and 67 of the main control and communication chip U1. Pins 2 and 3 of chip U3 are connected to resistor R30. Pin 4 of chip U3 is connected to resistor R49 and is connected to pin 32 of the main control and communication chip U1. Pin 6 of chip U3 is connected to resistors R55 and R50 and is connected to pin 1 of terminal P3. Pin 7 of chip U3 is connected to resistor R47 and is connected to pin 2 of terminal P3. Pin 8 of chip U3 is connected to capacitor C31 and is connected to pin 3 of terminal P3. Resistor R42 and capacitor C34 are connected between pins 7 and 8 of chip U3. Resistor R81 is connected between pins 6 and 7 of chip U3. The SIM card reading circuit includes a self-ejecting SIM card slot SIM1. Pin 1 of the SIM card slot SIM1 is connected to a diode D4, a capacitor C9, and a resistor R11 and is connected to pin 8 of the main control and communication chip U1. The resistor R11 is connected to pin 6 of the SIM card slot SIM1. Pin 3 of the SIM card slot SIM1 is connected to a diode D3, a capacitor C11, and a resistor R13 and is connected to pin 7 of the main control and communication chip U1. Pin 5 of the SIM card slot SIM1 is connected to a diode D6, a capacitor C12, and a resistor R14 and is connected to pin 5 of the main control and communication chip U1. Pin 6 of the SIM card slot SIM1 is connected to a diode D5, a capacitor C13, and a resistor R15 and is connected to pin 6 of the main control and communication chip U1.

4. The mainboard circuit for a voice intercom extension according to claim 1, characterized in that: The software programming circuit includes a TYPE-C interface J1. Pins A4 and A9 of the TYPE-C interface J1 are connected. Pin A9 of the TYPE-C interface J1 is connected to a diode D12 and a capacitor C25 and is connected to pin 28 of the main control and communication chip U1. Pin A5 of the TYPE-C interface J1 is connected to a resistor R22. Pin A6 of the TYPE-C interface J1 is connected to a diode D10 and is connected to pin 26 of the main control and communication chip U1. Pin A7 of the TYPE-C interface J1 is connected to a diode D11 and is connected to pin 27 of the main control and communication chip U1. Pins B4 and B9 of the TYPE-C interface J1 are connected to pin 28 of the main control and communication chip U1. Pin B5 of the TYPE-C interface J1 is connected to resistor R29. Pins B6 and B7 of the TYPE-C interface J1 are connected to pins 26 and 27 of the main control and communication chip U1, respectively.

5. The mainboard circuit for a voice intercom extension according to claim 1, characterized in that: The audio signal input circuit includes resistors R23 and R31. One end of resistors R23 and R31 is connected to pins 24 and 23 of the main control and communication chip U1, respectively. The other end of resistors R23 and R31 is connected to capacitors C17, C18, C16, C21, C22, C20, C24, and C23. One end of resistor R19 and capacitor C19 are connected between capacitors C16 and C20. The other end of resistor R19 is connected to pin 25 of the main control and communication chip U1. Resistors R32 and R28 are connected between capacitors C20 and C23. The other end of resistor R32 is connected to diode D9 and to pin 3 of terminal P2. The audio signal receiving and processing circuit includes resistors R39 and R35. One end of resistors R39 and R35 is connected to pins 21 and 22 of the main control and communication chip U1, respectively. The other end of resistor R39 is connected to capacitor C29. The other end of resistor R35 is connected to capacitors C27 and C28, diode D8, and resistor R21. The other ends of diode D8 and resistor R21 are connected to pin 4 of terminal P2.

6. The mainboard circuit for a voice intercom extension according to claim 1, characterized in that: The power indicator circuit includes two light-emitting diodes (LEDs) LED1. One end of one LED LED1 is connected to a resistor R9, and one end of the other LED LED1 is connected to one end of a resistor R3. The other end of the resistor R3 is connected to the collector of a transistor Q1. The base of the transistor Q1 is connected to a resistor R4 and is connected to pin 69 of the main control and communication chip U1. A resistor R6 is connected between the base and emitter of the transistor Q1.

7. The mainboard circuit for a voice intercom extension according to claim 5, characterized in that: The four-way switch control circuit includes transistors Q11, Q12, Q13, and Q14; The base of transistor Q11 is connected to one end of resistor R48 and resistor R61. The other end of resistor R48 is connected to pin 16 of the main control and communication chip U1. The collector of transistor Q11 is connected to one end of resistor R37. The other end of resistor R37 is connected to the base of transistor Q7. Resistor R8 is connected between the emitter and base of transistor Q7. The collector of transistor Q7 is connected to pin 5 of terminal P2. The base of transistor Q12 is connected to one end of resistor R51 and resistor R79. The other end of resistor R51 is connected to pin 14 of the main control and communication chip U1. The collector of transistor Q12 is connected to one end of resistor R38. The other end of resistor R38 is connected to the base of transistor Q8. Resistor R12 is connected between the emitter and base of transistor Q8. The collector of transistor Q8 is connected to pin 7 of terminal P2. The base of transistor Q13 is connected to one end of resistor R52 and resistor R27. The other end of resistor R52 is connected to pin 12 of the main control and communication chip U1. The collector of transistor Q13 is connected to one end of resistor R43. The other end of resistor R43 is connected to the base of transistor Q9. Resistor R25 is connected between the emitter and base of transistor Q9. The collector of transistor Q9 is connected to pin 9 of terminal P2. The base of transistor Q14 is connected to one end of resistor R60 and resistor R80. The other end of resistor R60 is connected to pin 10 of the main control and communication chip U1. The collector of transistor Q14 is connected to one end of resistor R45. The other end of resistor R45 is connected to the base of transistor Q10. Resistor R36 is connected between the emitter and base of transistor Q10. The collector of transistor Q10 is connected to pin 11 of terminal P2.

8. The mainboard circuit for a voice intercom extension according to claim 7, characterized in that: The four dial-up switching circuits on the switching board include transistors Q2, Q3, Q4, and Q5. The base of transistor Q2 is connected to resistor R5 and is connected to pin 10 of terminal P2. Resistor R64 is connected between the emitter and base of transistor Q2. One end of resistor R57 is connected to the collector of transistor Q2 and is connected to pin 11 of main control and communication chip U1. The other end of resistor R57 is connected to pin 76 of main control and communication chip U1. The base of transistor Q3 is connected to resistor R7 and is connected to pin 12 of terminal P2. Resistor R65 is connected between the emitter and base of transistor Q3. One end of resistor R58 is connected to the collector of transistor Q3 and is connected to pin 9 of main control and communication chip U1. The other end of resistor R58 is connected to pin 76 of main control and communication chip U1. The base of transistor Q4 is connected to resistor R18 and is connected to pin 6 of terminal P2. Resistor R40 is connected between the emitter and base of transistor Q4. One end of resistor R33 is connected to the collector of transistor Q4 and is connected to pin 15 of main control and communication chip U1. The other end of resistor R33 is connected to pin 76 of main control and communication chip U1. The base of transistor Q5 is connected to resistor R26 and is connected to pin 8 of terminal P2. Resistor R41 is connected between the emitter and base of transistor Q5. One end of resistor R34 is connected to the collector of transistor Q5 and is connected to pin 13 of main control and communication chip U1. The other end of resistor R34 is connected to pin 76 of main control and communication chip U1.

9. The mainboard circuit for a voice intercom extension according to claim 1, characterized in that: The network port circuit includes a main control chip U7. A resistor R75 and a crystal oscillator Y1 are connected between pins 10 and 11 of the main control chip U7. Pins 4, 5, 7, and 8 of the main control chip U7 are connected to pins 3, 6, 1, and 2 of the network port transformer HR911105A, respectively. One end of resistor R71, one end of resistor R72, one end of resistor R73, and one end of resistor R74 are connected between pins 4 and 5 of the network port transformer HR911105A. The other end of resistor R71 is connected to pin 1 of the HR911105A network transformer. The other end of resistor R72 is connected to pin 2 of the HR911105A network transformer. The other end of resistor R73 is connected to pin 6 of the HR911105A network transformer. The other end of resistor R74 is connected to pin 3 of the HR911105A network transformer. Resistors R76 and R77 are connected to pins 9 and 12 of the HR911105A network transformer, respectively.

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