Active Noise Canceling Automatic Telephone

Abstract

An active noise reduction automatic telephone includes an input and rectification circuit, an off-hook power supply control circuit, a dual audio dialing output control circuit, a voice amplification and side tone elimination circuit, an off-hook dialing noise interference prevention circuit, a handle voice output circuit, a head-mounted voice output circuit, an off-hook CPU power supply circuit, a control chip, an on-hook switching circuit, a voice input switching circuit, a voice signal transmission circuit, a DSP noise reduction module, and an on-hook CPU power supply circuit connected to the output end of the input and rectification circuit and the control chip; the off-hook CPU power supply circuit also supplies power to the on-hook switching circuit, and the voice signal transmission circuit is also connected to the anti-off-hook dialing noise interference circuit. In this way, the head-mounted voice input mode is used by default and the active noise reduction and head-mounted noise reduction modes are combined, and the noise reduction effect is good.

Description

Technical Field

[0001] The invention relates to the technical field of marine telephones, in particular to an active noise reduction automatic telephone. Background Art

[0002] The marine automatic telephone is used for daily work and communication between cabins on board. However, the marine automatic telephone is located in an environment with a lot of noise, such as the sound of the engine, the sound of the waves, and the sound of the operating machinery on board. When using the phone, it will be disturbed by the noise and it is difficult to hear the other party's voice clearly. If you miss or mishear important instructions, it will affect the safety of the ship's navigation.

[0003] In terms of noise reduction, two major technical schools have gradually formed, one is passive noise reduction (also known as physical noise reduction), and the other is active noise reduction (also known as active noise reduction). The technical characteristics of passive noise reduction are to use various characteristics of materials to reduce noise sources by means of isolation, shock absorption, damping, etc. Active noise reduction technology uses the characteristics of sound as a wave to eliminate noise by emitting reverse sound waves to offset the original sound waves and make them weaken or even disappear. However, there is still a demand for further noise reduction in the application of marine automatic telephones. Summary of the invention

[0004] In view of this, the present invention provides an active noise reduction automatic telephone which defaults to a head-mounted voice input mode and combines active noise reduction and head-mounted noise reduction modes and has a good noise reduction effect, so as to solve the above problems.

[0005] An active noise reduction automatic telephone comprises an input and rectification circuit, an off-hook power supply control circuit, a dual-audio dialing output control circuit, a voice amplification and side tone elimination circuit, an off-hook dialing noise interference prevention circuit, a handle voice output circuit, a headset voice output circuit, and an off-hook CPU power supply circuit connected to the output end of the off-hook power supply control circuit, a control chip connected to the output end of the off-hook CPU power supply circuit, an on-hook and off-hook switching circuit connected to the control chip, a voice input switching circuit connected to the on-hook and off-hook switching circuit, a voice signal transmission circuit connected to the voice input switching circuit, a DSP noise reduction module connecting the voice signal transmission circuit and the voice amplification and side tone elimination circuit, and an on-hook CPU power supply circuit connected to the output end of the input and rectification circuit and the control chip; the off-hook CPU power supply circuit also supplies power to the on-hook and off-hook switching circuit, and the voice signal transmission circuit is also connected to the anti-off-hook dialing noise interference circuit.

[0006] Furthermore, the input and rectification circuit includes a rectifier bridge DB, a first capacitor C1, a second capacitor C2, a third capacitor C3, a fourth capacitor C4, a first resistor R1, a second resistor R2, a third resistor R3, a first diode D1, a first connector CON1, and a varistor RV1; the positive electrode TIP of the external power supply is connected to the first input end of the rectifier bridge DB, the negative electrode RTN of the external power supply is connected to the second input end of the rectifier bridge DB, the first output end of the rectifier bridge DB is grounded, and the second output end is grounded through the first resistor R1, the second resistor R2, the third resistor R3 and the fourth capacitor C4; the first connector C ON1 is connected between the positive electrode TIP and the negative electrode RTN of the external power supply; the varistor RV1 is connected between the positive electrode TIP and the negative electrode RTN of the external power supply; the first input end of the rectifier bridge DB is also grounded through the first capacitor C1, and the second input end is also grounded through the second capacitor C2; the first end of the third capacitor C3 is connected to the node between the first resistor R1 and the second resistor R2, and the second end is grounded; the anode of the first diode D1 is connected to the node between the third resistor R3 and the fourth capacitor C4, and is also connected to the PDETE pin of the control chip, and the cathode of the first diode D1 is connected to a first DC power supply VDD.

[0007] Furthermore, the off-hook power supply control circuit includes a first transistor Q1, a second transistor Q2, a third transistor Q3, a fourth resistor R4, a fifth resistor R5, a sixth resistor R6, and a seventh resistor R7; the first transistor Q1 and the second transistor Q2 are both PNP transistors, and the third transistor Q3 is an NPN transistor; the output end of the rectifier bridge DB of the input and rectifier circuit is connected to the emitter of the first transistor Q1, and is also connected to the base of the first transistor Q1 through the fourth resistor R4, and the collector of the first transistor Q1 is connected to the off-hook CPU power supply circuit; the emitter of the second transistor Q2 is connected to the base of the first transistor Q1, and the base is connected to the output end of the rectifier bridge DB through the fifth resistor R5, and the collector of the second transistor Q2 is connected to the off-hook CPU power supply circuit; the collector of the third transistor Q3 is connected to the base of the second transistor Q2 through the sixth resistor R6, and the base is connected to the DP pin of the control chip through the seventh resistor R7.

[0008] Furthermore, the off-hook CPU power supply circuit includes a fourth transistor Q4, an eighth resistor R8, a ninth resistor R9, a fifth capacitor C5, a first voltage regulator DZ1 and a second voltage regulator DZ2; the fourth transistor Q4 is an NPN transistor; the collector of the fourth transistor Q4 is connected to the collector of the first transistor Q1 and the collector of the second transistor Q2; the base of the fourth transistor Q4 is connected to the collector of the first transistor Q1 through the eighth resistor R8, the emitter of the fourth transistor Q4 is connected to the first end of the ninth resistor R9, and the second end of the ninth resistor R9 is the first DC power supply VDD; the base of the fourth transistor Q4 is also grounded through the fifth capacitor C5, and is connected to the cathode of the first voltage regulator DZ1, and the anode of the first voltage regulator DZ1 is grounded; the anode of the second voltage regulator DZ2 is grounded, and the cathode is connected to the collector of the first transistor Q1.

[0009] Furthermore, the dual audio dialing output control circuit includes a fifth transistor Q5, a tenth resistor R10, an eleventh resistor R11, a sixth capacitor C6, a seventh capacitor C7, and an eighth capacitor C8; the fifth transistor Q5 is an NPN transistor; the collector of the fifth transistor Q5 is connected to the collector of the first transistor Q1, the base is connected to the DTMF pin of the control chip through the eleventh resistor R11, and the emitter is grounded through the tenth resistor R10; the collector of the fifth transistor Q5 is also grounded through the sixth capacitor C6; the base of the fifth transistor Q5 is connected to the DTMF pin through the seventh capacitor C7, and is also grounded through the eighth capacitor C8.

[0010] Further, the voice amplification and side-tone elimination circuit includes a sixth transistor Q6, a seventh transistor Q7, a second diode D2, a third diode D3, a twelfth resistor R12, a thirteenth resistor R13, a fourteenth resistor R14, a fifteenth resistor R15, a sixteenth resistor R16, a seventeenth resistor R17, an eighteenth resistor R18, a nineteenth resistor R19, a twentieth resistor R20, a twenty-first resistor R21, a twenty-second resistor R22, a twenty-third resistor R23, a ninth capacitor C9, a tenth capacitor C10, an eleventh capacitor C11, a twelfth capacitor C12, and a thirteenth capacitor C13 The sixth transistor Q6 is an NPN transistor, and the seventh transistor Q7 is a PNP transistor; the collector of the fifth transistor Q5 is connected to the emitter of the seventh transistor Q7, the base of the seventh transistor Q7 is connected to the collector of the fifth transistor Q5 through the twelfth resistor R12, the collector is connected to the first end of the twelfth capacitor C12 through the twenty-third resistor R23, and the second end of the twelfth capacitor C12 is grounded; the collector of the sixth transistor Q6 is connected to the base of the fifth transistor Q5, the base is connected to the collector of the fifth transistor Q5 through the fourteenth resistor R14 and the thirteenth resistor R13, and the emitter The first end of the ninth capacitor C9 is connected to the node between the fourteenth resistor R14 and the thirteenth resistor R13, and the second end is grounded; the first end of the tenth capacitor C10 is connected to the base of the sixth transistor Q6, and the second end is grounded; the base of the sixth transistor Q6 is also connected to the first end of the twelfth capacitor C12 through the twenty-first resistor R21, and the thirteenth capacitor C13 is connected in parallel with both ends of the twenty-first resistor R21; the twentieth resistor R20 connects the emitter of the sixth transistor Q6 and the collector of the seventh transistor Q7; the second diode D2 The anode of the transistor is connected to the collector of the seventh transistor Q7 through the nineteenth resistor R19, and the cathode is connected to the emitter of the sixth transistor Q6; the emitter of the seventh transistor Q7 is connected to the collector of the seventh transistor Q7 through the fifteenth resistor R15, the sixteenth resistor R16, and the eighteenth resistor R18; the eleventh capacitor C11 is connected in parallel to both ends of the fifteenth resistor R15; the first end of the seventeenth resistor R17 is connected to the node between the sixteenth resistor R16 and the eighteenth resistor R18, the second end is connected to the anode of the third diode D3, and the cathode of the third diode D3 is connected to the first end of the twelfth capacitor C12.

[0011] Further, the anti-off-hook dialing noise interference circuit includes a fourth diode D4, a fifth diode D5, a sixth diode D6, a seventh diode D7, an eighth diode D8, a third voltage regulator DZ3, a fourteenth capacitor C14, a fifteenth capacitor C15, a sixteenth capacitor C16, a seventeenth capacitor C17, an eighteenth capacitor C18, a twenty-fourth resistor R24, and a twenty-fifth resistor R25; a node between the sixteenth resistor R16 and the eighteenth resistor R18 is connected to a first end of the fourteenth capacitor C14, a second end of the fourteenth capacitor C14 is connected to an anode of the fourth diode D4 through the fifteenth capacitor C15 and the twenty-fourth resistor R24, and a cathode of the fourth diode D4 is connected to a MUTE pin of the control chip; a The second end is also grounded through the sixteenth capacitor C16; the seventeenth capacitor C17 is connected between the first end of the fourteenth capacitor C14 and the cathode of the third diode D3; the anode of the third voltage regulator DZ3 is grounded, and the cathode is connected to the cathode of the third diode D3; the anode of the fifth diode D5 is connected to the cathode of the third diode D3, and the cathode is connected to the anode of the sixth diode D6; the cathode of the sixth diode D6 is connected to the anode of the seventh diode D7; the cathode of the seventh diode D7 is connected to the anode of the eighth diode D8; the cathode of the eighth diode D8 is grounded; the cathode of the third diode D3 is also connected to the MUTE pin of the control chip through the twenty-fifth resistor R25; the first end of the eighteenth capacitor C18 is grounded, and the second end is connected to the handle voice output circuit.

[0012] Furthermore, the first end of the DSP noise reduction module is connected to the base of the sixth transistor Q6; the voice signal transmission circuit includes an eighth transistor Q8, a ninth diode D9, a twenty-sixth resistor R26, a twenty-seventh resistor R27, a twenty-eighth resistor R28, a twenty-ninth resistor R29, a nineteenth capacitor C19, a twentieth capacitor C20, a twenty-first capacitor C21, and a twenty-second capacitor C22; the eighth transistor Q8 is an NPN transistor; the anode of the ninth diode D9 is connected to the MUTE pin of the control chip, and is also grounded through the twenty-second capacitor C22; the ninth diode The cathode of the tube D9 is connected to the collector of the eighth triode Q8 through the twenty-sixth resistor R26, and is also connected to the second end of the DSP noise reduction module through the twenty-seventh resistor R27 and the nineteenth capacitor C19; the base of the eighth triode Q8 is connected to the node between the twenty-seventh resistor R27 and the twenty-sixth resistor R26 through the twenty-eighth resistor R28, and is also grounded through the twenty-first capacitor C21; the emitter of the eighth triode Q8 is grounded; the base of the eighth triode Q8 is also connected to the first end of the twentieth capacitor C20, and the second end of the twentieth capacitor C20 is grounded through the twenty-ninth resistor R29.

[0013] Furthermore, the on-hook and off-hook switching circuit includes a reed switch board HOOK, a first field effect transistor Q14, a second field effect transistor Q15, a forty-first resistor R41, and a forty-second resistor R42; the reed switch board HOOK has a first reed switch and a second reed switch, the first reed switch has a first normally open end HOOK1 and a first normally closed end HOOK2, and the second reed switch has a second normally open end HFMI and a second normally closed end HSMI; the first end of the first reed switch is connected to the first DC power supply VDD, and the second end can be selectively connected to the first normally open end HOOK1 and the first normally closed end HOOK2, the first normally open end HOOK1 is grounded through the forty-second resistor R42, and is connected to the gate of the first field effect transistor Q14; the drain of the first field effect transistor Q14 is connected to the HKS pin of the control chip, and the source is grounded; the first normally closed end HOOK2 is grounded through the forty-first resistor R41, and is connected to the gate of the second field effect transistor Q15; the drain and source of the second field effect transistor Q15 are both grounded.

[0014] Furthermore, the voice input switching circuit includes a switch SW, a handle microphone MIC and a head-mounted microphone HSMT; the first normally closed end HOOK2 is connected to the handle microphone MIC, and the second normally closed end HSMI is connected to the head-mounted microphone HSMT; the switch SW is arranged between the first reed switch and the second reed switch, the first end of the switch SW is connected to the second end of the twentieth capacitor C20, and the second end can be selectively connected to the first normally closed end HOOK2 or the second normally closed end HSMI; the first normally closed end HOOK2 is connected to the first end of the handle microphone MIC, and the second end of the handle microphone MIC is grounded; the second normally closed end HSMI is connected to the first end of the head-mounted microphone HSMT, and the second end of the head-mounted microphone HSMT is grounded.

[0015] Compared with the prior art, the active noise reduction automatic telephone of the present invention comprises an input and rectification circuit, an off-hook power supply control circuit, a dual audio dialing output control circuit, a voice amplification and side tone elimination circuit, an anti-off-hook dialing noise interference circuit, a handle voice output circuit, a head-mounted voice output circuit, and an off-hook CPU power supply circuit connected to the output end of the off-hook power supply control circuit, a control chip connected to the output end of the off-hook CPU power supply circuit, an on-hook switching circuit connected to the control chip, a voice input switching circuit connected to the on-hook switching circuit, a voice signal transmission circuit connected to the voice input switching circuit, a DSP noise reduction module connecting the voice signal transmission circuit and the voice amplification and side tone elimination circuit, and an on-hook CPU power supply circuit connected to the output end of the input and rectification circuit and the control chip; the off-hook CPU power supply circuit also supplies power to the on-hook switching circuit, and the voice signal transmission circuit is also connected to the anti-off-hook dialing noise interference circuit. In this way, the head-mounted voice input mode is defaulted and the active noise reduction and head-mounted noise reduction modes are combined, and the noise reduction effect is good. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The embodiments of the present invention are described below in conjunction with the accompanying drawings, wherein:

[0017] Figure 1 A block diagram of an active noise reduction automatic telephone provided by the present invention.

[0018] Figure 2 for Figure 1 Circuit diagram of the input and rectifier circuit.

[0019] Figure 3 for Figure 1 A circuit diagram of an off-hook power supply control circuit, an off-hook CPU power supply circuit and a dual-audio dialing output control circuit.

[0020] Figure 4 for Figure 1 Circuit diagram of the voice amplification and sidetone elimination circuit and DSP noise reduction module.

[0021] Figure 5 for Figure 1 A circuit diagram of a circuit for preventing off-hook dialing noise interference and a voice signal transmission circuit.

[0022] Figure 6 for Figure 1 Circuit diagram of the handle voice output circuit in FIG.

[0023] Figure 7 for Figure 1 Circuit diagram of the headset voice output circuit in FIG.

[0024] Figure 8 for Figure 1 A circuit diagram of the on-hook or off-hook switching circuit and the voice input switching circuit in FIG.

[0025] Fig. 9 for Figure 1 Circuit diagram of the on-hook CPU power supply circuit.

[0026] Fig.10 for Figure 1 Schematic diagram of the reed switch board and control chip in the figure. DETAILED DESCRIPTION

[0027] The specific embodiments of the present invention are further described in detail below based on the accompanying drawings. It should be understood that the description of the embodiments of the present invention herein is not intended to limit the protection scope of the present invention.

[0028] Please refer to Figure 1The active noise reduction automatic telephone provided by the present invention includes an input and rectification circuit 10, an off-hook power supply control circuit 20, a dual-audio dialing output control circuit 30, a voice amplification and side tone elimination circuit 40, an anti-off-hook dialing noise interference circuit 50, a handle voice output circuit 60, a headset voice output circuit 70, and an off-hook CPU power supply circuit 81 connected to the output end of the off-hook power supply control circuit 20, a control chip 82 connected to the output end of the off-hook CPU power supply circuit 81, an on-hook switching circuit 83 connected to the control chip 82, a voice input switching circuit 93 connected to the on-hook switching circuit 83, a voice signal transmission circuit 92 connected to the voice input switching circuit 93, a DSP noise reduction module 91 connecting the voice signal transmission circuit 92 and the voice amplification and side tone elimination circuit 40, and an on-hook CPU power supply circuit 84 connected to the output end of the input and rectification circuit 10.

[0029] The off-hook CPU power supply circuit 81 also supplies power to the on-hook and off-hook switching circuit 83 , and the voice signal transmission circuit 92 is also connected to the anti-off-hook dialing noise interference circuit 50 .

[0030] Please refer to Figure 2 The input and rectification circuit 10 includes a rectifier bridge DB, a first capacitor C1, a second capacitor C2, a third capacitor C3, a fourth capacitor C4, a first resistor R1, a second resistor R2, a third resistor R3, a first diode D1, a first connector CON1, and a varistor RV1. The grounding of the triangle and the grounding of the three-segment line are connected when the handset is removed; when the headphones are used, the grounding of the triangle and the grounding of the three-segment line are disconnected, and the circuits of the headphones and the handset are connected in series, which can provide higher current to the relevant circuits of the headphones and output higher sound signals.

[0031] The positive electrode TIP of the external power supply is connected to the first input terminal of the rectifier bridge DB, the negative electrode RTN of the external power supply is connected to the second input terminal of the rectifier bridge DB, the first output terminal of the rectifier bridge DB is grounded, and the second output terminal a is grounded through the first resistor R1, the second resistor R2, the third resistor R3 and the fourth capacitor C4.

[0032] The first connector CON1 is connected between the positive electrode TIP and the negative electrode RTN of the external power supply. The first connector CON1 is connected to an external switch to provide working power and transmit voice signals for the active noise reduction automatic telephone provided by the present invention.

[0033] The varistor RV1 is connected between the positive electrode TIP and the negative electrode RTN of the external power supply. The varistor RV1 plays a protective role when the voltage is too high.

[0034] The first input terminal of the rectifier bridge DB is also grounded through the first capacitor C1, and the second input terminal is also grounded through the second capacitor C2.

[0035] A first end of the third capacitor C3 is connected to a node between the first resistor R1 and the second resistor R2 , and a second end of the third capacitor C3 is grounded.

[0036] The anode of the first diode D1 is connected to the node between the third resistor R3 and the fourth capacitor C4, and is also connected to the PDETE pin of the control chip 82. The cathode of the first diode D1 is connected to the first DC power supply VDD. The PDETE pin is a parallel signal detection input.

[0037] Please refer to Figure 3 The off-hook power supply control circuit 20 includes a first transistor Q1, a second transistor Q2, a third transistor Q3, a fourth resistor R4, a fifth resistor R5, a sixth resistor R6, and a seventh resistor R7.

[0038] The first transistor Q1 and the second transistor Q2 are both PNP transistors, and the third transistor Q3 is an NPN transistor.

[0039] The second output terminal a of the rectifier bridge DB of the input and rectifier circuit 10 is connected to the emitter of the first transistor Q1, and is also connected to the base of the first transistor Q1 through the fourth resistor R4, and the collector of the first transistor Q1 is connected to the off-hook CPU power supply circuit 81. The output voltage of the second output terminal a of the rectifier bridge DB is 48V.

[0040] The emitter of the second transistor Q2 is connected to the base of the first transistor Q1 , the base is connected to the second output terminal a of the rectifier bridge DB through the fifth resistor R5 , and the collector of the second transistor Q2 is connected to the off-hook CPU power supply circuit 81 .

[0041] The collector of the third transistor Q3 is connected to the base of the second transistor Q2 through the sixth resistor R6, and the base is connected to the DP pin of the control chip 82 through the seventh resistor R7. The DP pin is the on-hook variable signal pin, which is used to control the on-hook circuit switching.

[0042] When the DP pin is at a high level, the third transistor Q3 is turned on, the second transistor Q2 is turned on, and the first transistor Q1 is turned on. The off-hook CPU power supply circuit 81 and subsequent circuits all act as loads, and the voltage is pulled down from 48V to about 7V (actually lower than 7V); when the DP pin is at a low level, the third transistor Q3 is turned off, the second transistor Q2 is turned off, and the first transistor Q1 is turned off. The off-hook CPU power supply circuit 81 and subsequent circuits are all cut off.

[0043] The off-hook CPU power supply circuit 81 includes a fourth transistor Q4, an eighth resistor R8, a ninth resistor R9, a fifth capacitor C5, a first voltage regulator DZ1 and a second voltage regulator DZ2. The fourth transistor Q4 is an NPN transistor. The fourth transistor Q4 functions to amplify current.

[0044] The collector of the fourth triode Q4 is connected to the collector of the first triode Q1 and the collector of the second triode Q2. The base of the fourth triode Q4 is connected to the collector of the first triode Q1 through the eighth resistor R8, and the emitter of the fourth triode Q4 is connected to the first end of the ninth resistor R9, and the second end of the ninth resistor R9 is the first DC power supply VDD. The base of the fourth triode Q4 is also grounded through the fifth capacitor C5, and is connected to the cathode of the first voltage regulator DZ1, the anode of the first voltage regulator DZ1 is grounded, the anode of the second voltage regulator DZ2 is grounded, and the cathode is connected to the collector of the first triode Q1.

[0045] The dual audio dialing output control circuit 30 includes a fifth transistor Q5, a tenth resistor R10, an eleventh resistor R11, a sixth capacitor C6, a seventh capacitor C7, and an eighth capacitor C8. The fifth transistor Q5 is an NPN transistor.

[0046] The collector b of the fifth triode Q5 is connected to the collector of the first triode Q1, the base is connected to the DTMF pin of the control chip 82 through the eleventh resistor R11, and the emitter is grounded through the tenth resistor R10. The collector b of the fifth triode Q5 is also grounded through the sixth capacitor C6. The base of the fifth triode Q5 is connected to the DTMF pin through the seventh capacitor C7 and is also grounded through the eighth capacitor C8.

[0047] The DTMF pin is a dual tone multi-frequency (DTMF) pin. The dual tone multi-frequency consists of a high frequency group and a low frequency group. Each high and low frequency group contains 4 frequencies. A high frequency signal and a low frequency signal are superimposed to form a combined signal, which represents a number. The DTMF signal has 16 codes. The DTMF signal can be used to select the corresponding phone to call.

[0048] The dual-tone dialing output control circuit 30 is used for output control of key signals. Dual-tone dialing means that a key press will generate two frequency signals to represent the key press, which is different from pulse dialing. It can be used to display the incoming call number.

[0049] Please refer to Figure 4The voice amplification and sidetone elimination circuit 40 includes a sixth transistor Q6, a seventh transistor Q7, a second diode D2, a third diode D3, a twelfth resistor R12, a thirteenth resistor R13, a fourteenth resistor R14, a fifteenth resistor R15, a sixteenth resistor R16, a seventeenth resistor R17, an eighteenth resistor R18, a nineteenth resistor R19, a twentieth resistor R20, a twenty-first resistor R21, a twenty-second resistor R22, a twenty-third resistor R23, a ninth capacitor C9, a tenth capacitor C10, an eleventh capacitor C11, a twelfth capacitor C12, and a thirteenth capacitor C13. The sixth transistor Q6 is an NPN transistor, and the seventh transistor Q7 is a PNP transistor.

[0050] The collector b of the fifth transistor Q5 is connected to the emitter of the seventh transistor Q7, the base of the seventh transistor Q7 is connected to the collector b of the fifth transistor Q5 through the twelfth resistor R12, the collector is connected to the first end of the twelfth capacitor C12 through the twenty-third resistor R23, and the second end of the twelfth capacitor C12 is grounded.

[0051] The collector of the sixth transistor Q6 is connected to the base of the fifth transistor Q5, the base is connected to the collector b of the fifth transistor Q5 through the fourteenth resistor R14 and the thirteenth resistor R13, and the emitter is connected to the first end of the twelfth capacitor C12 through the twenty-second resistor R22.

[0052] A first end of the ninth capacitor C9 is connected to a node between the fourteenth resistor R14 and the thirteenth resistor R13 , and a second end thereof is grounded.

[0053] The first end of the tenth capacitor C10 is connected to the base of the sixth transistor Q6, and the second end is grounded. The base of the sixth transistor Q6 is also connected to the first end of the twelfth capacitor C12 through the twenty-first resistor R21, and the thirteenth capacitor C13 is connected in parallel to both ends of the twenty-first resistor R21.

[0054] The twentieth resistor R20 connects the emitter of the sixth transistor Q6 and the collector of the seventh transistor Q7.

[0055] The anode of the second diode D2 is connected to the collector of the seventh transistor Q7 through the nineteenth resistor R19, and the cathode is connected to the emitter of the sixth transistor Q6.

[0056] The emitter of the seventh transistor Q7 is connected to the collector of the seventh transistor Q7 through the fifteenth resistor R15, the sixteenth resistor R16 and the eighteenth resistor R18. The eleventh capacitor C11 is connected in parallel to both ends of the fifteenth resistor R15.

[0057] The first end of the seventeenth resistor R17 is connected to the node c between the sixteenth resistor R16 and the eighteenth resistor R18 , the second end is connected to the anode of the third diode D3 , and the cathode d of the third diode D3 is connected to the first end of the twelfth capacitor C12 .

[0058] The first end of the DSP noise reduction module 91 is connected to the base of the sixth transistor Q6. The second end e of the DSP noise reduction module 91 is connected to the voice signal transmission circuit 92. The DSP noise reduction module 91 adopts the PI-36 digital DSP long-distance pickup noise reduction module. The module adopts a dual-core DSP chip with a unique and efficient noise reduction algorithm, which has an effect on both steady-state and non-steady-state noise. The PI-36 digital DSP long-distance pickup noise reduction module is an adaptive working mode. It has the same AGC function while suppressing environmental noise, and can meet the pickup range of 30cm-700cm. The sampling frequency of its main chip is 16KHZ, the normal mode working current is 20mA, and the noise reduction index is 30-36db. It can effectively solve the interference of environmental background noise in various voice calls and recording pickup, and obtain a voice signal with a higher signal-to-noise ratio.

[0059] The emitter of the sixth transistor Q6 and the collector of the seventh transistor Q7 are used to generate electrical signals with opposite phases to cancel each other out, and the twentieth resistor R20 is used to adjust the strength of the anti-phase electrical signal to eliminate the side tone.

[0060] Please refer to Figure 5 The anti-off-hook dialing noise interference circuit 50 includes a fourth diode D4, a fifth diode D5, a sixth diode D6, a seventh diode D7, an eighth diode D8, a third voltage regulator tube DZ3, a fourteenth capacitor C14, a fifteenth capacitor C15, a sixteenth capacitor C16, a seventeenth capacitor C17, an eighteenth capacitor C18, a twenty-fourth resistor R24, and a twenty-fifth resistor R25.

[0061] A node c between the sixteenth resistor R16 and the eighteenth resistor R18 is connected to a first end of a fourteenth capacitor C14, a second end f of the fourteenth capacitor C14 is connected to an anode of a fourth diode D4 via a fifteenth capacitor C15 and a twenty-fourth resistor R24, and a cathode of the fourth diode D4 is connected to a MUTE pin of the control chip 82. The second end f of the fourteenth capacitor C14 is also grounded via a sixteenth capacitor C16.

[0062] The seventeenth capacitor C17 is connected between the first end of the fourteenth capacitor C14 and the cathode d of the third diode D3. The anode of the third voltage regulator tube DZ3 is grounded, and the cathode is connected to the cathode d of the third diode D3.

[0063] The anode of the fifth diode D5 is connected to the cathode d of the third diode D3, and the cathode is connected to the anode of the sixth diode D6; the cathode of the sixth diode D6 is connected to the anode of the seventh diode D7; the cathode of the seventh diode D7 is connected to the anode of the eighth diode D8; and the cathode of the eighth diode D8 is grounded.

[0064] The cathode d of the third diode D3 is also connected to the MUTE pin of the control chip 82 through the twenty-fifth resistor R25.

[0065] The first end of the eighteenth capacitor C18 is grounded, and the second end g is connected to the handle voice output circuit 60.

[0066] The voice signal transmission circuit 92 includes an eighth transistor Q8, a ninth diode D9, a twenty-sixth resistor R26, a twenty-seventh resistor R27, a twenty-eighth resistor R28, a twenty-ninth resistor R29, a nineteenth capacitor C19, a twentieth capacitor C20, a twenty-first capacitor C21, and a twenty-second capacitor C22. The eighth transistor Q8 is an NPN transistor.

[0067] The anode of the ninth diode D9 is connected to the MUTE pin of the control chip 82, and is also grounded through the twenty-second capacitor C22. The cathode of the ninth diode D9 is connected to the collector of the eighth transistor Q8 through the twenty-sixth resistor R26, and is also connected to the second end e of the DSP noise reduction module 91 through the twenty-seventh resistor R27 and the nineteenth capacitor C19.

[0068] The base of the eighth transistor Q8 is connected to a node between the twenty-seventh resistor R27 and the twenty-sixth resistor R26 through the twenty-eighth resistor R28 and is also grounded through the twenty-first capacitor C21.

[0069] The emitter of the eighth transistor Q8 is grounded.

[0070] The base of the eighth transistor Q8 is also connected to the first end of the twentieth capacitor C20, and the second end h of the twentieth capacitor C20 is grounded through the twenty-ninth resistor R29.

[0071] The MUTE pin is a mute pin. When dialing, the potential of MUTE is pulled low, and the voltage of the eighth transistor Q8 is insufficient, so that external noise cannot be transmitted, thereby shielding the interference of external noise on the dialing audio.

[0072] The dynamic coil of the handset or the headphone generates a voice signal, which is transmitted through the eighth transistor Q8 and transmitted to the second end e of the DSP noise reduction module 91.

[0073] Please refer to Figure 6The handle voice output circuit 60 includes a ninth transistor Q9, a tenth transistor Q10, a handle speaker REC1, a thirtieth resistor R30, a thirty-first resistor R31, a thirty-second resistor R32, a thirty-third resistor R33, a thirty-fourth resistor R34, a thirty-fifth resistor R35, a twenty-third capacitor C23, and a twenty-fourth capacitor C24. The ninth transistor Q9 and the tenth transistor Q10 are both NPN transistors.

[0074] The base of the ninth transistor Q9 is connected to the second end f of the fourteenth capacitor C14, the collector is connected to the second end g of the eighteenth capacitor C18 through the thirtieth resistor R30, and the emitter is grounded through the thirty-first resistor R31.

[0075] The base of the thirteenth transistor Q10 is connected to the collector of the ninth transistor Q9, the collector is connected to the second end g of the eighteenth capacitor C18 through the thirty-third resistor R33, the emitter is grounded through the thirty-fifth resistor R35 and connected to the base of the ninth transistor Q9 through the thirty-fourth resistor R34. The twenty-fourth capacitor C24 is connected in parallel to both ends of the thirty-fifth resistor R35. The first end of the handle speaker REC1 is connected to the second end g of the eighteenth capacitor C18, and the second end i is connected to the emitter of the ninth transistor Q9 through the thirty-second resistor R32. The twenty-third capacitor C23 is connected in parallel between the first end and the second end i of the handle speaker REC1.

[0076] Please refer to Figure 7 The head-mounted voice output circuit 70 includes an eleventh transistor Q11, a twelfth transistor Q12, a thirteenth transistor Q13, a fourth voltage regulator DZ4, a tenth diode D10, an eleventh diode D11, a head-mounted speaker REC2, a thirty-sixth resistor R36, a thirty-seventh resistor R37, a thirty-eighth resistor R38, a thirty-ninth resistor R39, a fortieth resistor R40, a twenty-fifth capacitor C25, a twenty-sixth capacitor C26, a twenty-seventh capacitor C27, a twenty-eighth capacitor C28, a twenty-ninth capacitor C29, a thirtieth capacitor C30, a thirty-first capacitor C31, and a thirty-second capacitor C32. The eleventh transistor Q11 and the thirteenth transistor Q13 are both NPN transistors, and the twelfth transistor Q12 is a PNP transistor.

[0077] The first end of the twenty-fifth capacitor C25 is connected to the second end i of the handle speaker REC1 through the thirty-sixth resistor R36, and the second end is connected to the base of the eleventh transistor Q11. The collector of the eleventh transistor Q11 is connected to the base of the twelfth transistor Q12, and the emitter is grounded. The base of the eleventh transistor Q11 is also grounded through the twenty-sixth capacitor C26.

[0078] The emitter of the twelfth transistor Q12 is connected to the second end of the twenty-fifth capacitor C25 through the thirty-seventh resistor R37, and the collector is grounded. The base of the twelfth transistor Q12 is also grounded through the twenty-seventh capacitor C27. The twenty-ninth capacitor C29 is connected in parallel to both ends of the thirty-seventh resistor R37.

[0079] A first end of the head mounted speaker REC2 is connected to the emitter of the twelfth transistor Q12 via a twenty-eighth capacitor C28, and a second end is grounded.

[0080] The emitter of the thirteenth transistor Q13 is connected to the emitter of the twelfth transistor Q12, the base is connected to the first end of the thirtieth capacitor C30 through the thirty-eighth resistor R38, the second end of the thirtieth capacitor C30 is connected to the emitter of the twelfth transistor Q12. The collector of the thirteenth transistor Q13 is connected to the first end of the thirtieth capacitor C30 through the thirty-ninth resistor R39.

[0081] The anode of the tenth diode D10 is connected to the base of the thirteenth transistor Q13 , and the cathode is connected to the anode of the eleventh diode D11 ; the cathode of the eleventh diode D11 is connected to the base of the twelfth transistor Q12 .

[0082] The collector of the thirteenth transistor Q13 is grounded, and is also grounded through the fortieth resistor R40, the thirty-first capacitor C31, and the thirty-second capacitor C32, and is also connected to the cathode of the fourth voltage-stabilizing tube DZ4, and the anode of the fourth voltage-stabilizing tube DZ4 is grounded. When the headphones are used, these grounded components perform filtering and voltage stabilization between the two grounds.

[0083] Please refer to Figure 8 The on-hook and off-hook switching circuit 83 includes a reed switch board HOOK, a first field effect transistor Q14, a second field effect transistor Q15, a forty-first resistor R41, and a forty-second resistor R42.

[0084] Please also refer to Fig.10 The reed switch board HOOK has a first reed switch and a second reed switch, the first reed switch has a first normally open end HOOK1 and a first normally closed end HOOK2, and the second reed switch has a second normally open end HFMI and a second normally closed end HSMI. The first normally closed end HOOK2 is connected to the handle microphone MIC, and the second normally closed end HSMI is connected to the head-mounted microphone HSMT.

[0085] The first end of the first reed switch is connected to the first DC power supply VDD, and the second end can be selectively connected to the first normally open end HOOK1 and the first normally closed end HOOK2.

[0086] The first normally open terminal HOOK1 is grounded through the forty-second resistor R42, and is connected to the gate of the first field effect transistor Q14; the drain of the first field effect transistor Q14 is connected to the HKS pin of the control chip 82, and the source is grounded. The HKS pin is a start signal input pin. When the handset is picked up, the first reed switch jumps to the first normally closed terminal HOOK2, the first field effect transistor Q14 is turned off, and the HKS pin is pulled high, thereby giving the CPU an off-hook signal.

[0087] The first normally closed end HOOK2 is grounded through a forty-first resistor R41, and is connected to the gate of the second field effect transistor Q15; the drain and source of the second field effect transistor Q15 are both grounded.

[0088] The voice input switching circuit 93 includes a switch SW, a handset microphone MIC and a head mounted microphone HSMT.

[0089] The switch SW is arranged between the first reed switch and the second reed switch, and is used to realize the simultaneous operation of the first reed switch and the second reed switch. When the first reed switch is connected to the first normally closed end HOOK2, the second reed switch is connected to the second normally open end HFMI; when the first reed switch is connected to the first normally open end HOOK1, the second reed switch is connected to the second normally closed end HSMI.

[0090] The first end of the switch SW is connected to the second end h of the twentieth capacitor C20, and the second end can be selectively connected to the first normally closed end HOOK2 or the second normally closed end HSMI. The first normally closed end HOOK2 is connected to the first end of the handle microphone MIC, and the second end of the handle microphone MIC is grounded. The second normally closed end HSMI is connected to the first end of the head-mounted microphone HSMT, and the second end of the head-mounted microphone HSMT is grounded.

[0091] The head mounted speaker REC2 and the head mounted microphone HSMT are arranged on the headphone.

[0092] There is a magnet in the handset, which is used to attract the two reed switches on the reed switch board when powered on, so the jump of the first reed switch and the second reed switch is synchronized. When the handset is picked up, the first reed switch jumps to the first normally closed end HOOK2, and the HKS pin provides an off-hook signal; at the same time, the second reed switch jumps to the second normally open end HFMI, at which time the handset microphone MIC works and the head-mounted microphone HSMT does not work. Conversely, the first reed switch is connected to the first normally open end HOOK1, and the second reed switch is connected to the second normally closed end HSMI, at which time the head-mounted microphone HSMT is in working state.

[0093] Please refer to Fig. 9The CPU power supply circuit 84 includes a 14th transistor Q16, a 15th transistor Q17, a 16th transistor Q18, a 17th transistor Q19, a 12th diode D12, a 43rd resistor R43, a 44th resistor R44, a 45th resistor R45, a 46th resistor R46, a 47th resistor R47, a 48th resistor R48, a 49th resistor R49, a 33rd capacitor C33, a 34th capacitor C34, and a 35th capacitor C35. The 14th transistor Q16 is a PNP transistor, and the 15th transistor Q17, the 16th transistor Q18, and the 17th transistor Q19 are all NPN transistors.

[0094] The cathode of the twelfth diode D12 is connected to the first DC power supply VDD and is grounded through the thirty-third capacitor C33, and the anode is connected to the collector of the fourteenth triode Q16; the emitter of the fourteenth triode Q16 is connected to the second output terminal a of the rectifier bridge DB through the forty-seventh resistor R47, and the base is connected to the forty-seventh resistor R47 through the forty-third resistor R43. The collector of the fifteenth triode Q17 is connected to the base of the fourteenth triode Q16, the emitter is connected to the collector of the fourteenth triode Q16, and the base is grounded through the thirty-fourth capacitor C34. The emitter of the fifteenth triode Q17 is also grounded through the forty-fourth resistor R44 and the forty-fifth resistor R45.

[0095] The base of the sixteenth transistor Q18 is connected to the node between the forty-fourth resistor R44 and the forty-fifth resistor R45, the collector is connected to the forty-seventh resistor R47 through the forty-sixth resistor R46, and the emitter is grounded.

[0096] The collector of the seventeenth transistor Q19 is connected to the second output terminal a of the rectifier bridge DB through the forty-eighth resistor R48, the base is connected to the DTTMF0 pin of the control chip 82 through the forty-ninth resistor R49, and is also grounded through the thirty-fifth capacitor C35, and the emitter is grounded. The DTTMF0 pin is a reserved dual-tone multi-frequency input identification terminal.

[0097] When hanging up, only the control chip 82 and a small number of components need to be powered, and the on-hook CPU power supply circuit 84 steals power on the signal line to maintain the working state without affecting the normal operation of other telephones; when picking up the phone (including the handle mode and the headset mode), the power consumption is relatively large, and the off-hook power supply control circuit 20 needs to be specially powered.

[0098] Please refer to Fig.10 The reed switch board HOOK has a first normally open terminal HOOK1, a first normally closed terminal HOOK2, a voice output terminal Sound, a power supply terminal VDD, a second normally open terminal HFMI, and a second normally closed terminal HSMI.

[0099] The model of the control chip 82 is D63040TP, which has a power terminal VDD, a ground terminal GND, a PDETE pin, a DP pin, a DTME pin, a MUTE pin, a HKS pin, a DTTMF0 pin, etc.

[0100] Compared with the prior art, the active noise reduction automatic telephone of the present invention includes an input and rectification circuit 10, an off-hook power supply control circuit 20, a dual-audio dialing output control circuit 30, a voice amplification and side tone elimination circuit 40, an anti-off-hook dialing noise interference circuit 50, a handle voice output circuit 60, a headset voice output circuit 70, and an off-hook CPU power supply circuit 81 connected to the output end of the off-hook power supply control circuit 20, a control chip 82 connected to the output end of the off-hook CPU power supply circuit 81, an on-hook switching circuit 83 connected to the control chip 82, a voice input switching circuit 93 connected to the on-hook switching circuit 83, a voice signal transmission circuit 92 connected to the voice input switching circuit 93, a DSP noise reduction module 91 connecting the voice signal transmission circuit 92 and the voice amplification and side tone elimination circuit 40, and an on-hook CPU power supply circuit 84 connected to the output end of the input and rectification circuit 10; the off-hook CPU power supply circuit 81 also supplies power to the on-hook switching circuit 83, and the voice signal transmission circuit 92 is also connected to the anti-off-hook dialing noise interference circuit 50. In this way, the head-mounted voice input mode is used by default and it combines active noise reduction and head-mounted noise reduction, with good noise reduction effect.

[0101] The above are only preferred embodiments of the present invention and are not intended to limit the protection scope of the present invention. Any modification, equivalent substitution or improvement within the spirit of the present invention is included in the scope of the claims of the present invention.

Claims

1. An active noise reduction automatic telephone, characterized in that: It includes an input and rectification circuit, an off-hook power supply control circuit, a dual-tone multi-frequency dialing output control circuit, a voice amplification and sidetone cancellation circuit, an anti-off-hook dialing noise interference circuit, a handset voice output circuit, a headset voice output circuit connected in sequence, an off-hook CPU power supply circuit connected to the output end of the off-hook power supply control circuit, a control chip connected to the output end of the off-hook CPU power supply circuit, an off-hook / on-hook switching circuit connected to the control chip, a voice input switching circuit connected to the off-hook / on-hook switching circuit, a voice signal transmission circuit connected to the voice input switching circuit, a DSP noise reduction module connecting the voice signal transmission circuit and the voice amplification and sidetone cancellation circuit, and a on-hook CPU power supply circuit connected to both the output end of the input and rectification circuit and the control chip; the off-hook CPU power supply circuit also supplies power to the off-hook / on-hook switching circuit, and the voice signal transmission circuit is also connected to the anti-off-hook dialing noise interference circuit.

2. The active noise reduction automatic telephone according to claim 1, characterized in that: The input and rectification circuit includes a rectifier bridge DB, a first capacitor C1, a second capacitor C2, a third capacitor C3, a fourth capacitor C4, a first resistor R1, a second resistor R2, a third resistor R3, a first diode D1, a first connector CON1, a varistor RV1; the positive pole TIP of the external power supply is connected to the first input end of the rectifier bridge DB, the negative pole RTN of the external power supply is connected to the second input end of the rectifier bridge DB, the first output end of the rectifier bridge DB is grounded, and the second output end is grounded through the first resistor R1, the second resistor R2, the third resistor R3 and the fourth capacitor C4; the first connector CON1 is connected between the positive pole TIP and the negative pole RTN of the external power supply; the varistor RV1 is connected between the positive pole TIP and the negative pole RTN of the external power supply; the first input end of the rectifier bridge DB is also grounded through the first capacitor C1, and the second input end is also grounded through the second capacitor C2; the first end of the third capacitor C3 is connected to the node between the first resistor R1 and the second resistor R2, and the second end is grounded; the anode of the first diode D1 is connected to the node between the third resistor R3 and the fourth capacitor C4, and is also connected to the PDETE pin of the control chip, and the cathode of the first diode D1 is connected to a first DC power supply VDD.

3. The active noise reduction automatic telephone according to claim 2, characterized in that: The off-hook power supply control circuit includes a first triode Q1, a second triode Q2, a third triode Q3, a fourth resistor R4, a fifth resistor R5, a sixth resistor R6, and a seventh resistor R7; both the first triode Q1 and the second triode Q2 are PNP-type triodes, and the third triode Q3 is an NPN-type triode; the output terminal of the rectifier bridge DB of the input and rectifier circuit is connected to the emitter of the first triode Q1, and is also connected to the base of the first triode Q1 through the fourth resistor R4, and the collector of the first triode Q1 is connected to the off-hook CPU power supply circuit; the emitter of the second triode Q2 is connected to the base of the first triode Q1, the base is connected to the output terminal of the rectifier bridge DB through the fifth resistor R5, and the collector of the second triode Q2 is connected to the off-hook CPU power supply circuit; the collector of the third triode Q3 is connected to the base of the second triode Q2 through the sixth resistor R6, and the base is connected to the DP pin of the control chip through the seventh resistor R7.

4. The active noise reduction automatic telephone according to claim 3, characterized in that: The off-hook CPU power supply circuit includes a fourth triode Q4, an eighth resistor R8, a ninth resistor R9, a fifth capacitor C5, a first voltage regulator diode DZ1, and a second voltage regulator diode DZ2; the fourth triode Q4 is an NPN-type triode; the collector of the fourth triode Q4 is connected to both the collector of the first triode Q1 and the collector of the second triode Q2; the base of the fourth triode Q4 is connected to the collector of the first triode Q1 through the eighth resistor R8, the emitter of the fourth triode Q4 is connected to the first end of the ninth resistor R9, and the second end of the ninth resistor R9 is the first DC power supply VDD; the base of the fourth triode Q4 is also grounded through the fifth capacitor C5 and is connected to the cathode of the first voltage regulator diode DZ1, and the anode of the first voltage regulator diode DZ1 is grounded; the anode of the second voltage regulator diode DZ2 is grounded, and the cathode is connected to the collector of the first triode Q1.

5. The active noise reduction automatic telephone according to claim 3, characterized in that: The dual-tone multi-frequency dialing output control circuit includes a fifth triode Q5, a tenth resistor R10, an eleventh resistor R11, a sixth capacitor C6, a seventh capacitor C7, and an eighth capacitor C8; the fifth triode Q5 is an NPN-type triode; the collector of the fifth triode Q5 is connected to the collector of the first triode Q1, the base is connected to the DTMF pin of the control chip through the eleventh resistor R11, and the emitter is grounded through the tenth resistor R10; the collector of the fifth triode Q5 is also grounded through the sixth capacitor C6; the base of the fifth triode Q5 is connected to the DTMF pin through the seventh capacitor C7 and is also grounded through the eighth capacitor C8.

6. The active noise reduction automatic telephone according to claim 5, characterized in that: The voice amplification and sidetone cancellation circuit includes a sixth triode Q6, a seventh triode Q7, a second diode D2, a third diode D3, a twelfth resistor R12, a thirteenth resistor R13, a fourteenth resistor R14, a fifteenth resistor R15, a sixteenth resistor R16, a seventeenth resistor R17, an eighteenth resistor R18, a nineteenth resistor R19, a twentieth resistor R20, a twenty-first resistor R21, a twenty-second resistor R22, a twenty-third resistor R23, a ninth capacitor C9, a tenth capacitor C10, an eleventh capacitor C11, a twelfth capacitor C12, and a thirteenth capacitor C13; the sixth triode Q6 is an NPN type triode, and the seventh triode Q7 is a PNP type triode; the collector of the fifth triode Q5 is connected to the emitter of the seventh triode Q7, the base of the seventh triode Q7 is connected to the collector of the fifth triode Q5 through the twelfth resistor R12, the collector is connected to the first end of the twelfth capacitor C12 through the twenty-third resistor R23, and the second end of the twelfth capacitor C12 is grounded; the collector of the sixth triode Q6 is connected to the base of the fifth triode Q5, the base is connected to the collector of the fifth triode Q5 through the fourteenth resistor R14 and the thirteenth resistor R13, and the emitter is connected to the first end of the twelfth capacitor C12 through the twenty-second resistor R22; the first end of the ninth capacitor C9 is connected to the node between the fourteenth resistor R14 and the thirteenth resistor R13, and the second end is grounded; the first end of the tenth capacitor C10 is connected to the base of the sixth triode Q6, and the second end is grounded; the base of the sixth triode Q6 is also connected to the first end of the twelfth capacitor C12 through the twenty-first resistor R21, and the thirteenth capacitor C13 is connected in parallel across both ends of the twenty-first resistor R21; the twentieth resistor R20 connects the emitter of the sixth triode Q6 and the collector of the seventh triode Q7; the anode of the second diode D2 is connected to the collector of the seventh triode Q7 through the nineteenth resistor R19, and the cathode is connected to the emitter of the sixth triode Q6; the emitter of the seventh triode Q7 is connected to the collector of the seventh triode Q7 through the fifteenth resistor R15, the sixteenth resistor R16, and the eighteenth resistor R18; the eleventh capacitor C11 is connected in parallel across both ends of the fifteenth resistor R15; the first end of the seventeenth resistor R17 is connected to the node between the sixteenth resistor R16 and the eighteenth resistor R18, and the second end is connected to the anode of the third diode D3, and the cathode of the third diode D3 is connected to the first end of the twelfth capacitor C12.

7. The active noise reduction automatic telephone according to claim 6, characterized in that: The anti-disconnection machine dialing noise interference circuit includes a fourth diode D4, a fifth diode D5, a sixth diode D6, a seventh diode D7, an eighth diode D8, a third voltage regulator diode DZ3, a fourteenth capacitor C14, a fifteenth capacitor C15, a sixteenth capacitor C16, a seventeenth capacitor C17, an eighteenth capacitor C18, a twenty-fourth resistor R24, and a twenty-fifth resistor R25; the node between the sixteenth resistor R16 and the eighteenth resistor R18 is connected to the first end of the fourteenth capacitor C14, the second end of the fourteenth capacitor C14 is connected to the anode of the fourth diode D4 through the fifteenth capacitor C15 and the twenty-fourth resistor R24, and the cathode of the fourth diode D4 is connected to the MUTE pin of the control chip; the second end of the fourteenth capacitor C14 is also grounded through the sixteenth capacitor C16; the seventeenth capacitor C17 is connected between the first end of the fourteenth capacitor C14 and the cathode of the third diode D3; the anode of the third voltage regulator diode DZ3 is grounded, and the cathode is connected to the cathode of the third diode D3; the anode of the fifth diode D5 is connected to the cathode of the third diode D3, and the cathode is connected to the anode of the sixth diode D6; the cathode of the sixth diode D6 is connected to the anode of the seventh diode D7; the cathode of the seventh diode D7 is connected to the anode of the eighth diode D8; the cathode of the eighth diode D8 is grounded; the cathode of the third diode D3 is also connected to the MUTE pin of the control chip through the twenty-fifth resistor R25; the first end of the eighteenth capacitor C18 is grounded, and the second end is connected to the handset voice output circuit.

8. The active noise reduction automatic telephone according to claim 7, characterized in that: the first end of the DSP noise reduction module is connected to the base of the sixth triode Q6; the voice signal transmission circuit includes an eighth triode Q8, a ninth diode D9, a twenty-sixth resistor R26, a twenty-seventh resistor R27, a twenty-eighth resistor R28, a twenty-ninth resistor R29, a nineteenth capacitor C19, a twentieth capacitor C20, a twenty-first capacitor C21, and a twenty-second capacitor C22; the eighth triode Q8 is an NPN type triode; the anode of the ninth diode D9 is connected to the MUTE pin of the control chip and is also grounded through the twenty-second capacitor C22; the cathode of the ninth diode D9 is connected to the collector of the eighth triode Q8 through the twenty-sixth resistor R26 and is also connected to the second end of the DSP noise reduction module through the twenty-seventh resistor R27 and the nineteenth capacitor C19; the base of the eighth triode Q8 is connected to the node between the twenty-seventh resistor R27 and the twenty-sixth resistor R26 through the twenty-eighth resistor R28 and is also grounded through the twenty-first capacitor C21; the emitter of the eighth triode Q8 is grounded; the base of the eighth triode Q8 is also connected to the first end of the twentieth capacitor C20, and the second end of the twentieth capacitor C20 is grounded through the twenty-ninth resistor R29.

9. The active noise reduction automatic telephone according to claim 8, characterized in that: The off-hook and on-hook switching circuit includes a reed switch board HOOK, a first field-effect transistor Q14, a second field-effect transistor Q15, a forty-first resistor R41, and a forty-second resistor R42; the reed switch board HOOK has a first reed switch and a second reed switch. The first reed switch has a first normally open terminal HOOK1 and a first normally closed terminal HOOK2, and the second reed switch has a second normally open terminal HFMI and a second normally closed terminal HSMI; the first end of the first reed switch is connected to the first DC power supply VDD, and the second end is selectively connected to the first normally open terminal HOOK1 and the first normally closed terminal HOOK2. The first normally open terminal HOOK1 is grounded through the forty-second resistor R42 and is simultaneously connected to the gate of the first field-effect transistor Q14; the drain of the first field-effect transistor Q14 is connected to the HKS pin of the control chip, and the source is grounded; the first normally closed terminal HOOK2 is grounded through the forty-first resistor R41 and is simultaneously connected to the gate of the second field-effect transistor Q15; both the drain and the source of the second field-effect transistor Q15 are grounded.

10. The active noise-canceling automatic telephone according to claim 9, characterized in that: the voice input switching circuit includes a switch SW, a handset microphone MIC, and a headset microphone HSMT; the first normally closed terminal HOOK2 is connected to the handset microphone MIC, and the second normally closed terminal HSMI is connected to the headset microphone HSMT; the switch SW is arranged between the first reed switch and the second reed switch. The first end of the switch SW is connected to the second end of the twentieth capacitor C20, and the second end is selectively connected to the first normally closed terminal HOOK2 or the second normally closed terminal HSMI; the first normally closed terminal HOOK2 is connected to the first end of the handset microphone MIC, and the second end of the handset microphone MIC is grounded; the second normally closed terminal HSMI is connected to the first end of the headset microphone HSMT, and the second end of the headset microphone HSMT is grounded.

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