Three-network integration terminal circuit and three-network integration fixed telephone

Abstract

The utility model provides a three-network integration terminal circuit and a three-network integration fixed-line telephone. The three-network integration terminal circuit comprises a 5G system total module, a power supply circuit, a fixed-line telephone control circuit, a conversation circuit, a PSTN conversation control circuit and a VOIP conversation module. When an enterprise puts forward requirements for internal / remote office, internal communication and international services, the three-network integration terminal circuit is applied to a fixed telephone, and the three-network integration terminal circuit integrates three functions of 5G, PSTN and VOIP, so that the scheme can meet the requirements of the enterprise, and is convenient for a client to carry out communication operation according to the requirements; therefore, the fixed telephone can be used in a wide range of scenes, such as families, individual households, group companies, public institutions, international companies and the like, and the use cost is low.

Description

Technical Field

[0001] The present disclosure relates to the field of communication technology, and in particular to a triple-network convergence terminal circuit and a triple-network convergence fixed-line telephone. Background Art

[0002] As people's material lives become more affluent, the market for landline voice terminals is shrinking. Companies are now targeting differentiated, customized, and targeted application scenarios. Currently, there are different types of landline phones on the market, but some only support 4G, while others only support VOIP.

[0003] The PSTN network within an enterprise provides a free internal voice exchange environment and is the primary method for internal voice communication. However, for international business communications or voice communication with clients supporting Internet calling, VOIP is the primary method. However, when some enterprises require simultaneous office, internal, and international business operations, they need to add PSTN-capable landlines for internal communication, VOIP-capable landlines for international business, and 4G / 5G landlines for external voice communication. This limits the use cases of each landline type and increases costs. Utility Model Content

[0004] The purpose of the present disclosure is to overcome the shortcomings of the existing technology and provide a three-network convergence terminal circuit and a three-network convergence fixed-line telephone that can integrate 5G, PSTN and VOIP and has a wide range of applicable scenarios.

[0005] The purpose of this disclosure is achieved through the following technical solutions:

[0006] A triple-network integration terminal circuit, comprising:

[0007] 5G system total module;

[0008] A power supply circuit, wherein the input end of the power supply circuit is used to connect to an external power supply, and the power output end of the power supply circuit is electrically connected to the power end of the 5G system main module;

[0009] A landline control circuit, wherein the transceiver end of the landline control circuit is electrically connected to the transceiver end of the 5G system master module;

[0010] A call circuit, wherein the call control terminal of the 5G system master module is electrically connected to the call input terminal of the call circuit, and the output terminal of the call circuit is used to output an audio signal;

[0011] A PSTN call control circuit, wherein a signal control terminal of the PSTN call control circuit is electrically connected to a signal enable terminal of the landline control circuit, and an audio control terminal of the PSTN call control circuit is electrically connected to an audio terminal of the call circuit;

[0012] The VOIP call module is installed in the 5G system main module.

[0013] In one embodiment, the call circuit includes a handle call circuit and a hands-free call circuit, the handle audio output ends of the 5G system main module and the PSTN call control circuit are electrically connected to the call input end of the handle call circuit, and the handle call circuit is used to output a handle audio signal, the hands-free audio output ends of the 5G system main module and the PSTN call control circuit are electrically connected to the call input end of the hands-free call circuit, and the output end of the hands-free call circuit is used to output a hands-free audio signal.

[0014] In one embodiment, the PSTN call control circuit includes a PSTN switch circuit and a PSTN audio circuit, the switch control enable end of the PSTN switch circuit is electrically connected to the input end of the landline control circuit, the audio control end of the PSTN audio circuit is electrically connected to the audio end of the call circuit, and the call input end of the landline control circuit is electrically connected to the call output end of the PSTN audio circuit.

[0015] In one embodiment, the PSTN switch circuit includes a PSTN switch main circuit and a PSTN audio gain adjustment circuit, the current output end of the PSTN switch main circuit is electrically connected to the PSTN audio gain adjustment circuit, and the PSTN audio gain adjustment circuit is used to adjust the audio gain.

[0016] In one embodiment, the PSTN switch main circuit includes a PSTN switch control subcircuit, a PSTN incoming call circuit and a signal voltage conversion output circuit. The voltage stabilizing output end of the PSTN switch control subcircuit is electrically connected to the input end of the PSTN incoming call circuit and the signal voltage conversion output circuit respectively. The notification output end of the PSTN incoming call circuit is electrically connected to the notification receiving end of the landline control circuit. The ringtone enabling end of the signal voltage conversion output circuit is electrically connected to the ringtone signal receiving end of the landline control circuit.

[0017] In one embodiment, the PSTN incoming call circuit includes a first optocoupler, a first resistor and a second resistor, the first end of the first optocoupler is connected to the voltage-stabilized output end of the PSTN switch control subcircuit, the second end of the first optocoupler is connected to the signal voltage conversion output circuit, the first end of the first resistor is connected to a standard power supply, the second end of the first resistor is connected to the fourth end of the first optocoupler, the first end of the second resistor is connected to the input end of the landline control circuit, the second end of the second resistor is connected to the third end of the first optocoupler, and the third end of the first optocoupler is grounded.

[0018] In one embodiment, the PSTN incoming call circuit further includes a first capacitor and a third resistor, wherein the upper end of the first capacitor is connected to the second end of the second resistor and the first end of the third resistor, respectively, and the second end of the third resistor is connected to the lower end of the first capacitor and the third end of the first optocoupler, respectively, and the lower end of the first capacitor is grounded.

[0019] In one embodiment, the landline control circuit includes a fixed-line central processor and a PSTN-5G universal asynchronous receiver and transmitter. The transceiver end of the fixed-line central processor is electrically connected to the transceiver end of the PSTN-5G universal asynchronous receiver and transmitter, the transceiver ends of the PSTN-5G universal asynchronous receiver and transmitter are electrically connected to the transceiver end of the 5G system main module, the dialing output end of the fixed-line central processor is electrically connected to the input end of the PSTN audio circuit, and the incoming call signal enabling end of the PSTN switch circuit is electrically connected to the incoming call signal receiving end of the fixed-line central processor.

[0020] In one embodiment, the landline control circuit further includes a fourth resistor and a second capacitor, the first end of the fourth resistor being connected to the dual-tone multi-frequency signal control end of the fixed-line central processor, the second end of the fourth resistor being connected to the dual-tone multi-frequency signal enable end of the PSTN audio circuit and the upper half end of the second capacitor, and the lower half end of the second capacitor being grounded.

[0021] A triple-network converged fixed-line telephone comprises the triple-network converged terminal circuit described in any one of the above embodiments.

[0022] Compared with the prior art, the present disclosure has at least the following advantages:

[0023] When enterprises have demands for internal / remote offices, internal communications and international business, the triple-network convergence terminal circuit is applied to fixed-line phones. Since the triple-network convergence terminal circuit integrates 5G, PSTN and VOIP functions into one, the solution can meet the needs of enterprises and facilitate customers to carry out communication operations for the above needs. Therefore, the use scenarios of this fixed-line phone are relatively broad, such as being suitable for families, individual households, group companies, institutions, international companies and other scenarios, and the cost of use is relatively low. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions of the embodiments of the present disclosure, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present disclosure and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without creative work.

[0025] Figure 1 This is a circuit diagram of a 5G system master module of a triple-network convergence terminal circuit in one embodiment;

[0026] Figure 2 for Figure 1 The remaining circuit diagram of the 5G system total module is shown;

[0027] Figure 3 For Figure 1 A circuit diagram of a power supply circuit connected to the 5G system master module shown;

[0028] Figure 4 For Figure 1 The circuit diagram of the landline control circuit connected to the 5G system master module shown, wherein the fixed-line central processor is connected to the 5G system master module via a PSTN-5G universal asynchronous receiver and transmitter;

[0029] Figure 5 For Figure 1 Circuit diagram of the handset call circuit in the call circuit connected to the 5G system master module shown;

[0030] Figure 6 For Figure 1 A circuit diagram of a hands-free call circuit in a call circuit connected to a 5G system master module is shown;

[0031] Figure 7 For the respective Figure 4 The base control circuit shown and Figure 5 and Figure 6 A circuit diagram of a PSTN call control circuit connected to the call circuit shown, wherein the PSTN call control circuit includes a PSTN switch circuit and a PSTN audio circuit;

[0032] Figure 8 for Figure 7 The circuit diagram of the PSTN switch main line in the PSTN switch circuit shown;

[0033] Figure 9 for Figure 7 The circuit diagram of the PSTN audio circuit in the PSTN switch circuit is shown.

[0034] Figure 1: 100, 5G system main module; 200, power supply circuit; 300, landline control circuit; 310, landline central processing unit; 320, PSTN-5G universal asynchronous receiver and transmitter; 400, call circuit; 410, handle call circuit; 420, hands-free call circuit; 500, PSTN call control circuit; 510, PSTN switch circuit; 511, PSTN switch main line; 512, PSTN audio gain adjustment circuit; 520, PSTN audio circuit. DETAILED DESCRIPTION

[0035] To facilitate understanding of the present disclosure, a more comprehensive description of the present disclosure will be provided below with reference to the accompanying drawings. The accompanying drawings illustrate preferred embodiments of the present disclosure. However, the present disclosure can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and comprehensive understanding of the disclosure.

[0036] It should be noted that when an element is referred to as being "fixed to" another element, it may be directly attached to the other element or there may be an intermediate element. When an element is referred to as being "connected to" another element, it may be directly connected to the other element or there may be an intermediate element. The terms "vertical," "horizontal," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only implementation methods.

[0037] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this disclosure pertains. The terms used herein in the specification of this disclosure are intended only to describe specific embodiments and are not intended to limit this disclosure. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0038] In order to better understand the technical solutions and beneficial effects of the present disclosure, the present disclosure is further described in detail below with reference to specific embodiments:

[0039] See also Figures 1 to 7, which is a three-network integration terminal circuit of an embodiment of the present invention, including a 5G system main module 100, a power circuit 200, a landline control circuit 300, a call circuit 400, a PSTN call control circuit 500 and a VOIP call module; the input end of the power circuit 200 is used to connect to an external power supply, and the power output end of the power circuit 200 is electrically connected to the power end of the 5G system main module 100; the transceiver end of the landline control circuit 300 is electrically connected to the transceiver end of the 5G system main module 100; the call control end of the 5G system main module 100 is electrically connected to the call input end of the call circuit 400, and the output end of the call circuit 400 is used to output an audio signal; the signal control end of the PSTN call control circuit 500 is electrically connected to the signal enable end of the landline control circuit 300, and the audio control end of the PSTN call control circuit 500 is electrically connected to the audio end of the call circuit 400; the VOIP call module is installed in the 5G system main module 100.

[0040] It can be understood that the 5G system main module 100 supports 5G, PSTN and VOIP calls, and also has a Bluetooth antenna, a WIFI antenna and a 5G antenna, so that the terminal circuit can communicate in more ways, making it easier for more customers to operate on the fixed-line phones using the terminal circuit, so that the fixed-line phones can be used in more scenarios. Specifically, when the enterprise has demands for internal / remote office, internal communication and international business, the three-network convergence terminal circuit is applied to the fixed-line phone. Since the three-network convergence terminal circuit integrates 5G, PSTN and VOIP functions into one, the solution can meet the needs of the enterprise and facilitate customers to perform communication operations for the above needs. Therefore, the fixed-line phone can be used in a wider range of scenarios, such as families, individual households, group companies, institutions, international companies and other scenarios, and the cost of use is relatively low.

[0041] like Figure 5 and Figure 6 As shown, in one embodiment, the call circuit 400 includes a handle call circuit 410 and a hands-free call circuit 420. The handle audio output terminals of the 5G system master module 100 and the PSTN call control circuit 500 are electrically connected to the call input terminal of the handle call circuit 410. The handle call circuit 410 is used to output a handle audio signal. The hands-free audio output terminals of the 5G system master module 100 and the PSTN call control circuit 500 are electrically connected to the call input terminal of the hands-free call circuit 420. The output terminal of the hands-free call circuit 420 is used to output a hands-free audio signal. It can be understood that, in combination with Figure 1As shown, when making a 5G call or a VOIP call, you can make a call either through hands-free or by picking up the handle. When making a call through hands-free, the 5G system main module 100 enables the hands-free handset signal through the SPK_P and SPK_M pins, and enables the hands-free MIC signal to the hands-free call circuit 420 through the MIC3_P and MIC3_M pins, so that the customer can make a call through the hands-free step; when making a call through the handle, the 5G system main module 100 enables the handle MIC signal through the MIC1_P and MIC1_M pins, and enables the handle handset signal to the handle call circuit 410 through the EAR_P and EAR_M pins, so that the customer can make a call through the handle step. Of course, you can also make a PSTN call through the hands-free or handle, and then combine it with Figure 7 As shown, when a hands-free call is made, the PSTN call signal is directed to the hands-free call circuit 420 for a hands-free call; when a handle is used to make a call, the PSTN call signal is directed to the handle call circuit 410 for a handle call.

[0042] like Figure 7 As shown, in one embodiment, the PSTN call control circuit 500 includes a PSTN switch circuit 510 and a PSTN audio circuit 520, combined with Figures 4 to 6 As shown, the switch control enable terminal of the PSTN switch circuit 510 is electrically connected to the input terminal of the base control circuit 300, the audio control terminal of the PSTN audio circuit 520 is electrically connected to the audio terminal of the call circuit 400, and the call input terminal of the base control circuit 300 is electrically connected to the call output terminal of the PSTN audio circuit 520. Figure 8 and Figure 9As shown, PSTN switch circuit 510 includes a PSTN switch main circuit 511 and a PSTN audio gain adjustment circuit 512. The current output end of PSTN switch main circuit 511 is electrically connected to PSTN audio gain adjustment circuit 512, which is used to adjust the audio gain. It is understood that when making a PSTN call, gain control adjustment is required due to changes in the PSTN telephone line. Transistors Q203 and Q204 of PSTN audio gain adjustment circuit 512 are used for AGC control (Automatic Gain Control). When the length of the external user line varies, the external line voltage varies, resulting in different conduction levels of transistors Q203 and Q204. This in turn causes different conduction levels of optocoupler U202, transistors Q215, and transistors Q216, further causing different PSTN audio line signal attenuation, thereby automatically adjusting the audio gain. When an incoming call signal enters the PSTN call control circuit 500, the loop is first opened through the PSTN switch circuit 510. Then, the signal reaches the landline control circuit 300 through the PSTN audio circuit 520, so that the landline control circuit 300 notifies the 5G system main module 100 to start the ringing.

[0043] In another embodiment, the call input end of the handle call circuit 410 is electrically connected to the handle audio output end of the 5G system main module 100 and the PSTN audio circuit 520, and the call input end of the hands-free call circuit 420 is electrically connected to the hands-free audio output end of the 5G system main module 100 and the PSTN audio circuit 520, respectively.

[0044] Furthermore, if Figure 8As shown, the PSTN switch main circuit 511 includes a PSTN switch control subcircuit, a PSTN incoming call circuit, and a signal voltage conversion output circuit. The voltage-regulated output terminal of the PSTN switch control subcircuit is electrically connected to the input terminals of the PSTN incoming call circuit and the signal voltage conversion output circuit, respectively. The notification output terminal of the PSTN incoming call circuit is electrically connected to the notification receiving terminal of the base station control circuit 300, and the ringing enable terminal of the signal voltage conversion output circuit is electrically connected to the ringing signal receiving terminal of the base station control circuit 300. It will be understood that when a PSTN call is made, the PSTN switch control subcircuit is activated via the telephone line, and the telephone line current also flows through the signal voltage conversion output circuit. Generally, the telephone line voltage is relatively high and needs to be stepped down by transformer T201 before being output to the PSTN audio circuit 520. When there is an incoming call signal on the telephone line, the incoming call signal is turned on by the optocoupler U201. Subsequently, the signal flows to the base station control circuit 300, causing the base station control circuit 300 to notify the 5G system master module 100 to initiate the ringing. Furthermore, the PSTN switch control subcircuit includes a first telephone line interface J1 and a second telephone line interface J2, a varistor VDR1, a Zener diode group (Zener diode Z213 and Zener diode Z214), an inductor L3 and a rectifier switch output subcircuit. The first end and the second end of the varistor VDR1 are electrically connected between the first telephone line interface J1 and the second telephone line interface J2, respectively. The first end of the inductor L3 is connected to the first end of the varistor VDR1, and the second end of the inductor L3 is connected to the input end of the rectifier switch output subcircuit. The output end of the rectifier switch output subcircuit is connected to the PSTN audio gain adjustment circuit 512. The first end of the Zener diode group is connected to the first end of the inductor L3, and the second end of the Zener diode group is connected to the PSTN incoming call circuit. Among them, the varistor VDR1 is used for lightning protection. Since the three-network integration terminal circuit is applied in many scenarios, when using PSTN communication, there is a situation where the telephone line has a higher voltage. If it is in severe weather conditions, there is also the possibility of attracting lightning. Therefore, the varistor VDR1 is set for lightning protection to ground the lightning signal and protect the circuit components from being destroyed by the lightning voltage. The inductor L3 is used to prevent interference with the communication signal and reduce the situation where the signal voltage fluctuates greatly, ensuring normal calls when using PSTN. When an incoming call signal passes from the telephone line through the first telephone line interface J1 and the second telephone line interface J2, it will break through the voltage regulator diode group and reach the PSTN incoming call circuit.

[0045] Furthermore, if Figure 8 As shown, the PSTN incoming call circuit includes a first optical coupler U201, a first resistor R51 and a second resistor R356, combined with Figure 4As shown, the first terminal of the first optocoupler U201 is connected to the voltage-stabilizing output terminal of the PSTN switch control subcircuit, the second terminal of the first optocoupler U201 is connected to the signal voltage conversion output circuit, the first terminal of the first resistor R51 is connected to the standard power supply, the second terminal of the first resistor R51 is connected to the fourth terminal of the first optocoupler U201, the first terminal of the second resistor R356 is connected to the input terminal of the base phone control circuit 300, the second terminal of the second resistor R356 is connected to the third terminal of the first optocoupler U201, and the third terminal of the first optocoupler U201 is grounded. It can be understood that when the incoming call signal breaks through the voltage-stabilizing diode group of the PSTN switch control subcircuit, the first optocoupler U201 is turned on. After conduction, the current from the standard power supply is output to the base phone control circuit 300 through the first resistor R51, the first optocoupler U201, and the second resistor R356 in sequence. This enables the base phone control circuit 300 to enable the ringing signal to be transmitted to the 5G system main module 100, causing it to trigger the ringing tone, thereby notifying the user of the incoming call information.

[0046] like Figure 8 As shown, in one embodiment, the PSTN incoming call circuit further includes a first capacitor C96 and a third resistor R355. The upper end of the first capacitor C96 is connected to the second end of the second resistor R356 and the first end of the third resistor R355, respectively. The second end of the third resistor R355 is connected to the lower end of the first capacitor C96 and the third end of the first optocoupler U201, respectively. The lower end of the first capacitor C96 is grounded. It can be understood that when an incoming call signal is output to the base phone control circuit 300, the first capacitor C96 and the third resistor R355 are connected in parallel to form a resistor-capacitor circuit, which filters the incoming call signal, thereby preventing significant fluctuations and interference in the current signal and ensuring that the base phone control circuit 300 can subsequently properly enable the ringtone signal to the 5G system master module 100.

[0047] like Figure 4 As shown, in one embodiment, the landline control circuit 300 includes a fixed-line central processor 310 and a PSTN-5G universal asynchronous receiver and transmitter 320, combined with Figure 1As shown, the transceiver terminals MCU_SDA_T and MCU_SDA_R of the fixed-line central processor 310 are electrically connected to the transceiver terminal of the PSTN-5G universal asynchronous receiver / transmitter 320, the transceiver terminals 5G_TXD and 5G_RXD of the PSTN-5G universal asynchronous receiver / transmitter 320 are electrically connected to the transceiver terminals UART0_TXD and UART0_RXD of the 5G system master module 100, the dialing output terminal of the fixed-line central processor 310 is electrically connected to the input terminal of the PSTN audio circuit 520, and the incoming call signal enable terminal of the PSTN switch circuit 510 is electrically connected to the incoming call signal receiving terminal of the fixed-line central processor 310. It can be understood that the fixed-line central processor 310 and the 5G system master module 100 need to communicate through the PSTN-5G universal asynchronous receiver / transmitter 320 so that communication information can be sent and received between the fixed-line central processor 310 and the 5G system master module 100 through the PSTN-5G universal asynchronous receiver / transmitter 320. In this embodiment, the incoming call signal controlled terminal of the fixed-line central processor 310 is electrically connected to the incoming call signal output terminal of the PSTN incoming call circuit of the PSTN main switch 511. When an incoming call signal arrives, the signal passes through the PSTN incoming call circuit and enters the fixed-line central processor 310. The fixed-line central processor 310 then enables the ringing signal and notifies the 5G system master module 100 via the PSTN-5G universal asynchronous receiver and transmitter 320, causing it to start the ringing sound to notify the user.

[0048] like Figure 4 As shown, in one embodiment, the base control circuit 300 further includes a fourth resistor R204 and a second capacitor C191, combined with Figure 7 As shown, the first end of the fourth resistor R204 is connected to the dual-tone multi-frequency signal control terminal DTMF of the fixed-line central processor 310, and the second end of the fourth resistor R204 is respectively connected to the dual-tone multi-frequency signal enable terminal of the PSTN audio circuit 520 and the upper half of the second capacitor C191, and the lower half of the second capacitor C191 is grounded. It can be understood that when making a call using the PSTN, the 5G system main module 100 notifies the fixed-line central processor 310 to enable the dual-tone multi-frequency signal, which is then provided to the telephone outside-the-office switch through the resistor R314 and the capacitor C143 through the output amplifier IC203-A to conduct the call. The fourth resistor R204 is used to limit the enabled signal current to reduce the possibility of the fixed-line central processor 310 being destroyed due to excessive current. The second capacitor C191 is used to filter the dual-tone multi-frequency signal to reduce the interference of redundant signals and ensure the quality of the PSTN call.

[0049] The present disclosure also provides a triple-network converged fixed-line telephone, comprising the triple-network converged terminal circuit of any one of the above embodiments.

[0050] Compared with the prior art, the present disclosure has at least the following advantages:

[0051] When enterprises have demands for internal / remote offices, internal communications and international business, the triple-network convergence terminal circuit is applied to fixed-line phones. Since the triple-network convergence terminal circuit integrates 5G, PSTN and VOIP functions into one, the solution can meet the needs of enterprises and facilitate customers to carry out communication operations for the above needs. Therefore, the use scenarios of this fixed-line phone are relatively broad, such as being suitable for families, individual households, group companies, institutions, international companies and other scenarios, and the cost of use is relatively low.

[0052] The above-described embodiments merely represent several implementation methods of the present disclosure. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the disclosed patent. It should be noted that a person of ordinary skill in the art may make various modifications and improvements without departing from the scope of the present disclosure, all of which fall within the scope of protection of the present disclosure. Therefore, the scope of protection of the disclosed patent shall be determined by the appended claims.

Claims

1. A triple-network convergence terminal circuit, characterized in that: include: 5G system total module; A power supply circuit, wherein the input end of the power supply circuit is used to connect to an external power supply, and the power output end of the power supply circuit is electrically connected to the power end of the 5G system main module; A landline control circuit, wherein the transceiver end of the landline control circuit is electrically connected to the transceiver end of the 5G system master module; A call circuit, wherein the call control terminal of the 5G system master module is electrically connected to the audio terminal of the call circuit, and the output terminal of the call circuit is used to output an audio signal; A PSTN call control circuit, wherein a signal control terminal of the PSTN call control circuit is electrically connected to a signal enable terminal of the landline control circuit, and an audio control terminal of the PSTN call control circuit is electrically connected to an audio terminal of the call circuit; The VOIP call module is installed in the 5G system main module.

2. The triple-network convergence terminal circuit according to claim 1, characterized in that: The call circuit includes a handle call circuit and a hands-free call circuit. The handle audio output ends of the 5G system main module and the PSTN call control circuit are electrically connected to the call input end of the handle call circuit. The handle call circuit is used to output a handle audio signal. The hands-free audio output ends of the 5G system main module and the PSTN call control circuit are electrically connected to the call input end of the hands-free call circuit. The output end of the hands-free call circuit is used to output a hands-free audio signal.

3. The triple-network convergence terminal circuit according to claim 1, characterized in that: The PSTN call control circuit includes a PSTN switch circuit and a PSTN audio circuit. The switch control enable end of the PSTN switch circuit is electrically connected to the input end of the landline control circuit, the audio control end of the PSTN audio circuit is electrically connected to the audio end of the call circuit, and the call input end of the landline control circuit is electrically connected to the call output end of the PSTN audio circuit.

4. The triple-network integration terminal circuit according to claim 3, characterized in that: The PSTN switch circuit includes a PSTN switch main circuit and a PSTN audio gain adjustment circuit. The current output end of the PSTN switch main circuit is electrically connected to the PSTN audio gain adjustment circuit. The PSTN audio gain adjustment circuit is used to adjust the audio gain.

5. The triple-network integration terminal circuit according to claim 4, characterized in that: The PSTN switch main circuit includes a PSTN switch control subcircuit, a PSTN incoming call circuit and a signal voltage conversion output circuit. The voltage stabilizing output end of the PSTN switch control subcircuit is electrically connected to the PSTN incoming call circuit and the input end of the signal voltage conversion output circuit respectively. The notification output end of the PSTN incoming call circuit is electrically connected to the notification receiving end of the landline control circuit. The ringtone enabling end of the signal voltage conversion output circuit is electrically connected to the ringtone signal receiving end of the landline control circuit.

6. The triple-network integration terminal circuit according to claim 5, characterized in that: The PSTN incoming call circuit includes a first optocoupler, a first resistor and a second resistor. The first end of the first optocoupler is connected to the voltage-stabilizing output end of the PSTN switch control subcircuit, the second end of the first optocoupler is connected to the signal voltage conversion output circuit, the first end of the first resistor is connected to a standard power supply, the second end of the first resistor is connected to the fourth end of the first optocoupler, the first end of the second resistor is connected to the input end of the base phone control circuit, the second end of the second resistor is connected to the third end of the first optocoupler, and the third end of the first optocoupler is grounded.

7. The triple-network integration terminal circuit according to claim 6, characterized in that: The PSTN incoming call circuit also includes a first capacitor and a third resistor, the upper half of the first capacitor is respectively connected to the second end of the second resistor and the first end of the third resistor, the second end of the third resistor is respectively connected to the lower half of the first capacitor and the third end of the first optocoupler, and the lower half of the first capacitor is grounded.

8. The triple-network integration terminal circuit according to claim 3, characterized in that: The landline control circuit includes a fixed-line central processor and a PSTN-5G universal asynchronous receiver and transmitter. The transceiver end of the fixed-line central processor is electrically connected to the transceiver end of the PSTN-5G universal asynchronous receiver and transmitter, the transceiver ends of the PSTN-5G universal asynchronous receiver and transmitter are electrically connected to the transceiver end of the 5G system main module, the dialing output end of the fixed-line central processor is electrically connected to the input end of the PSTN audio circuit, and the incoming call signal enabling end of the PSTN switch circuit is electrically connected to the incoming call signal receiving end of the fixed-line central processor.

9. The triple-network integration terminal circuit according to claim 8, characterized in that: The landline control circuit also includes a fourth resistor and a second capacitor, a first end of the fourth resistor is connected to the dual-tone multi-frequency signal control end of the fixed-line central processor, a second end of the fourth resistor is respectively connected to the dual-tone multi-frequency signal enable end of the PSTN audio circuit and the upper half end of the second capacitor, and a lower half end of the second capacitor is grounded.

10. A triple-network integrated fixed-line telephone, characterized in that: It includes the triple-network integration terminal circuit according to any one of claims 1 to 9.

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