CN103108258B - A telephone intercom system - Google Patents

Abstract

The invention discloses a telephone intercom system, which comprises an incoming call detection circuit, an off-hook circuit, a modulation and demodulation module, a line selection module, a microcontroller, a storage module and an interface module. The incoming call detection circuit detects the incoming call status in the line and uploads it to the microcontroller. If an incoming call signal is detected, the micro-controller controls the line to connect to the off-hook circuit to complete the automatic off-hook operation; After receiving the on-hook signal, the control circuit disconnects the off-hook circuit to complete the automatic on-hook function. In addition, the microcontroller judges the current incoming call line according to the signals input by the two incoming call detection circuits, controls the line selection circuit, and connects the current input line to the modulation and demodulation module to realize normal communication. It can complete automatic off-hook, on-hook, and automatic switching between lines, that is, it supports multi-channel telephone communication, and has stronger adaptability and more convenient use.

Description

A telephone intercom system

technical field

The invention belongs to the field of telephone intercom, and in particular relates to a telephone intercom system capable of switching between different lines and automatically connecting and hanging up.

Background technique

The telephone intercom system is used for short-distance voice communication, such as indoor and outdoor calls installed in buildings, or intercom lines installed in units.

The existing intercom system adopts multiple communication terminals installed in various places, connects the microcontroller through the terminal, and the microcontroller selects the number terminal it calls, and the modem modulates and demodulates the sound signal accordingly, thereby It is better to complete the call transfer between users. However, it still has shortcomings: for a telephone intercom system with multiple lines installed in the same unit, it is impossible to switch between the lines to realize the call, so there is no way to conveniently make a call on any phone between the lines On the other hand, for some special occasions, it is necessary to automatically go off-hook when an incoming call is needed, and to automatically hang up when the phone is hung up. The present intercom system does not realize this problem.

Contents of the invention

The purpose of the present invention is to provide a telephone intercom system capable of switching between lines and automatically off-hook and on-hook, so as to improve its adaptability.

A telephone intercom system comprising:

Incoming call detection circuit: used to detect the incoming call status in the line;

Off-hook circuit: used to complete the off-hook protocol in the telephone communication standard;

Modulation and demodulation module: used to modulate and demodulate commands and voice signals in the line;

Line selection module: switch the line according to the current incoming call line or the line that needs to be dialed, and it is connected with the modem module;

Microcontroller: used to receive the detection signal of the incoming call detection circuit, control the off-hook circuit to perform automatic off-hook and on-hook operations according to the detection signal, receive the upload signal from the modulation and demodulation module, and issue control commands to the modulation and demodulation module. Input line after demodulation module modulation;

Storage module: connected to the microcontroller, used to store the internal telephone dialing number set by the user in advance;

Interface module: used to communicate with the external system host;

The voice amplification circuit amplifies the voice signal demodulated by the modem module and then puts it out through the speaker.

Using the telephone intercom system of the present invention, the communication terminal dials according to the dialing number pre-stored in the storage module, the dialing command is input into the interface module and then modulated by the modem and then transmitted through the line, and the incoming call detection circuit detects the state of the incoming call in the line and uploads it to the microcontroller . If an incoming call signal is detected, the micro-controller controls the line to connect to the off-hook circuit to complete the automatic off-hook operation; After receiving the on-hook signal, the control circuit disconnects the off-hook circuit to complete the automatic on-hook function. In addition, the microcontroller judges the current incoming call line according to the signals input by the two incoming call detection circuits, controls the line selection circuit, and connects the current input line to the modulation and demodulation module to realize normal communication. According to the number stored in the storage module set by the user in advance, the user can dial and call any one of the two telephone lines, and the microcontroller selects the line and finds the user machine corresponding to the number to control the line selection The module switches to the corresponding line. Compared with the prior art, the utility model can realize automatic off-hook and on-hook, and automatic switching between lines, that is, supports multi-channel telephone communication, and has stronger adaptability and more convenient use.

Preferably, after the detection signal of the incoming call detection circuit is filtered by a capacitor to filter out the DC voltage, the AC signal is converted into a DC pulse signal by bridge rectification, and is output by an optocoupler after being stabilized by a voltage regulator tube, filtered by a capacitor, and limited by a resistor. To the microcontroller input interface.

Preferably, the off-hook circuit includes a switch connected to a microcontroller, and the microcontroller controls the opening and closing of the switch corresponding to the off-hook and on-hook state changes.

Preferably, the switch is a triode, and the microcontroller controls the conduction or cut-off of the triode to realize the opening and closing of the relay.

Preferably, the line selection module is a relay, and the control pin of the relay is connected to the output interface of the microcontroller.

Preferably, the speech amplifying circuit includes a power amplifier and a filter, and the speech signal is amplified by the power amplifier and then filtered out by a filter for high-frequency interference signals before being output to the speaker.

Preferably, the interface module communicates with the external system host as a serial port circuit, and the serial port level conversion chip converts its communication level.

Preferably, the present invention also includes a one-key dialing circuit connected to the microcontroller, and the memory stores the corresponding call number in the one-key dialing module.

Description of drawings

1 is a schematic diagram of an incoming call detection circuit according to an embodiment of the present invention;

2 is a schematic diagram of an off-hook circuit according to an embodiment of the present invention;

3 is a schematic circuit diagram of a line selection module according to an embodiment of the present invention;

Fig. 4 is the circuit schematic diagram of microcontroller and memory module of the embodiment of the present invention;

Fig. 5 is the schematic diagram of the speech amplifying circuit of the embodiment of the present invention;

FIG. 6 is a schematic diagram of a modulation and demodulation module circuit according to an embodiment of the present invention;

7 is a schematic diagram of an interface module circuit according to an embodiment of the present invention;

FIG. 8 is a schematic diagram of a one-key dialing circuit;

FIG. 9 is a schematic diagram of a circuit block diagram of the present invention.

detailed description

Below in conjunction with accompanying drawing, the present invention will be further described.

In the telephone line detection circuit shown in Figure 1, when the telephone line is idle, there will be a 48V DC voltage, and when there is an incoming call, a 75V, 25Hz AC signal will be superimposed on the telephone line. The capacitor C16 in the circuit is used to isolate the 48V DC voltage, and the resistor R3 is used to limit the current to avoid excessive current and damage the back-end signal detection circuit. The rectifier diodes D1, D2, D4, and D5 form an AC-to-DC bridge circuit, and the regulator tube D3 stabilizes the output of the previous bridge circuit to 3V. Together, they convert the 75V, 25Hz AC signal into a 3V DC pulse signal. . Capacitor C15 is used to filter out the AC signal. Resistor R2 is a current limiting function to prevent the front-end output signal from being too strong and damage the optical coupler P1. Optical coupler P1 is used to isolate the electrical connection between the telephone input circuit and the microcontroller control circuit to avoid interference. After the previous circuit, the 3V DC pulse signal is correctly output to the P0.0 port of the microcontroller. R13 is the pull-up resistor of P0.0 port. After pre-written single-chip program, the software can automatically identify the electrical pulse signal.

The off-hook circuit shown in Figure 2, when the microcontroller pin P0.3 outputs a low level, the triode Q1 conducts, the relay H1 pulls in, and the relay pin 2 (H1_2) and the telephone line input socket pin 2 (TEL1_2 ) conduction. At this time, it is equivalent to adding a 680 ohm resistor R4 and a capacitor C17 on the two 48V DC lines of the telephone line. According to the telephone communication standard, the telephone exchange thinks that the telephone is in an off-hook state at this time.

If the user has set the automatic answering function in advance, when the microcontroller detects an incoming call through the P0.0 pin, it will output a low-level signal through the P0.3 pin to control the telephone line to enter the telephone off-hook circuit, thereby realizing the automatic answering function. If the user finishes talking and presses the on-hook button, the single-chip microcomputer outputs a high-level signal through the P0.3 pin, and controls the telephone line to enter the incoming call detection circuit, thereby realizing the on-hook function.

If the other party hangs up first, a 450Hz busy signal pulse will appear on the telephone line. When the MCU program detects this signal, it will think that the other party has hung up, and at the same time pull the P0. The machine is always in the busy state, and the other party cannot make an incoming call, so as to realize the automatic hang-up function.

As shown in Figure 3, the switching circuit module circuit diagram, the telephone signal detection circuit, can know which internal line the current incoming call is, and the single-chip program controls the P0.4 port to output high or low level, and controls the state of the relay H3, thereby controlling the output of the telephone line Whether the two lines A and B of the terminal circuit are connected to TEL1_1, TEL1_2, or to TEL2_1, TEL2_2. Realize the call selection of automatically switching the internal line of the telephone. If it is a local dial-up call, first let the P0.4 port of the single-chip microcomputer output the corresponding level, control the relay to switch the communication channel, and then dial.

Figure 4 is the circuit diagram of the microcontroller and storage module, U7 is the data storage chip 24C16B, which is used to store the telephone extension dial number set by the user in advance, and the data can still be saved in the power-off state. The data communication of the chip adopts the I2C interface, and the P2.6 and P2.7 of the local single-chip microcomputer simulate the I2C communication with the chip to realize writing number data and reading number data. The STC12C5A16S2 in the microcontroller circuit is a high-speed, high-reliability, dual-port single-chip microcomputer chip. The chip completes all the signal splitting and intelligent control functions of the machine, and the fixed program is burned into it when it leaves the factory. The serial port 0 of the chip is used to communicate with the telephone modem module, and the serial port 1 is used to communicate with the system control host outside the machine. C24 is the filter capacitor at the input end of the chip power supply. C18 and R6 form the power-on reset circuit of the chip. C21, C22 and Y1 form the clock circuit of the chip.

Fig. 5 is the voice amplification circuit diagram of the embodiment of the present invention, after this circuit amplifies the voice input by the other party, it directly outputs to an 8 ohm, 2W loudspeaker. The TDA2822 in the circuit is a low-power amplifier chip with wide operating voltage, low noise, good sound quality, high integration and few peripheral components. Resistor R29 in the circuit acts as a load for the front-end output. C27 is used to filter out the high frequency interference signal output by the front end. C3 is used to isolate the DC component of the front-end output. The adjustable resistor RP1 is used to adjust the output sound volume. Other components in the circuit are peripheral components required in the power amplifier chip circuit.

6 is a circuit diagram of the modulation and demodulation module of the embodiment of the present invention. This module realizes the signal modulation and demodulation function in the telephone line, can recognize the ringing signal and the busy tone signal, and can output the dialing signal to the telephone line. The module communicates with the MCU using the serial port. The module can upload various signals in the telephone line to the single-chip microcomputer, or the single-chip microcomputer sends dialing commands and telephone numbers to the module, and is modulated by the module into analog signals and output to the telephone line. A and B in Fig. 5 are two lines input in the telephone. RXD1 and TXD1 are the serial port pins for communicating with the microcontroller. PH-MIC-, PH_MIC+ are microphone input for phone calls. PH-SP+, PH_SP- are the voice output of the other party during the phone call.

Fig. 7 is a circuit diagram of the interface module of the embodiment of the present invention, that is, the TTL level is converted into the RS232 level. In order to improve the stability of communication, the communication between this machine and the external system host adopts RS232 level serial port communication protocol. Therefore, it is necessary to add a TTL to RS232 conversion circuit. The circuit also has an electrical isolation function. Completely electrically isolate the power supply, ground, and signal inside the machine from the external system host. Avoid external high-frequency interference signals from entering the unit, which will affect the sound quality of voice calls. ADM3251E is a high-speed, 2.5KV fully isolated (power and data) RS232 transceiver chip. It is very suitable for use in occasions where electrical isolation is required between the two sides of the communication. Other components are peripheral components required by the chip.

Figure 8 is a schematic diagram of a one-key dialing circuit. When the user presses a key in two extension lines, when the microcontroller detects the signal, it first controls the line selection circuit, switches the relay, and selects the connection between the modem module and the extension socket. connection between. Then, by reading the extension number stored by the user in advance, the number is sent to the modem module, and the modem module modulates and generates a dial signal to the line, thereby realizing the one-key dial function.

Fig. 9 is a schematic diagram of the overall circuit connection block diagram, which includes:

Incoming call detection circuit: used to detect the incoming call status in the line;

Off-hook circuit: used to complete the off-hook protocol in the telephone communication standard;

Modulation and demodulation module: used to modulate and demodulate commands and voice signals in the line;

Line selection module: switch the line according to the current incoming call line or the line that needs to be dialed, and it is connected with the modem module;

Microcontroller: used to receive the detection signal of the incoming call detection circuit, control the off-hook circuit to perform automatic off-hook and on-hook operations according to the detection signal, receive the upload signal from the modulation and demodulation module, and issue control commands to the modulation and demodulation module. Input line after demodulation module modulation;

Storage module: connected to the microcontroller, used to store the internal telephone dialing number set by the user in advance;

Interface module: used to communicate with the external system host;

The voice amplification circuit amplifies the voice signal demodulated by the modem module and puts it out through the speaker;

The one-key dialing circuit is connected with the controller, and the corresponding call number in the one-key dialing module is stored in the memory.

The technical solutions provided by the embodiments of the present invention have been introduced in detail above, and the principles and implementation modes of the embodiments of the present invention have been explained by using specific examples in this paper. The descriptions of the above embodiments are only applicable to help understand the embodiments of the present invention Principle; at the same time, for those skilled in the art, according to the embodiment of the present invention, there will be changes in the specific implementation and application scope. In summary, the content of this specification should not be construed as limiting the present invention.

Claims (7)

1. a telephone entry system, is characterized in that comprising:

Carry out power detection circuit: for detection of the electricity condition that comes in circuit;

Circuit for answering: for completing the off-hook agreement of telephonic communication standard;

Modulation /demodulation module: for the order of modulation and demodulation circuit and voice signal;

Circuit select module: according to current call circuit maybe need dialing circuit switching circuit, its withModulation /demodulation module connects;

Microcontroller: for receiving the detection signal of power detection circuit, control is plucked according to detection signalAutomatic off-hook, on-hook and automatic hand-up operation are carried out in dynamo-electric road, receive the upper of modulation /demodulation moduleThe number of delivering a letter, issues control command to modulation /demodulation module, input after the modulation of modulation /demodulation moduleCircuit;

Memory module: be connected with microcontroller, the inside connections dialing arranging in advance for storing userNumber;

Interface module: for external system main-machine communication;

Voice amplifying circuit, after voice signal after the demodulation of modulation /demodulation module is amplified by loudspeakerPut outward;

Described circuit for answering comprises the switch being connected with microcontroller, microprocessor control switchOpen and close corresponding automatic off-hook, on-hook and automatic hand-up state variation.

2. telephone entry system according to claim 1, is characterized in that, described come electro-detectionThe detection signal of circuit, after electric capacity filters DC voltage, changes into AC signal through bridge path rectificationDC pulse signal, by exporting to through optocoupler after voltage-stabiliser tube voltage stabilizing, capacitor filtering, resistance current limlitingMicrocontroller input interface.

3. telephone entry system according to claim 1, is characterized in that, described switch is oneTriode, the conducting of microprocessor control triode or cut-off realize the switching to relay.

4. telephone entry system according to claim 1, is characterized in that, described circuit is selectedModule is relay, and Control pin is connected with microcontroller output interface.

5. telephone entry system according to claim 1, is characterized in that, described voice amplifyCircuit comprises power amplifier and wave filter, after voice signal is amplified by power amplifier through filteringAfter device filtering high-frequency interferencing signal, export loudspeaker to.

6. telephone entry system according to claim 1, is characterized in that, described interface moduleWith external system main-machine communication be a serial port circuit, by serial ports electrical level transferring chip to its communication electricityFlat turn is changed.

7. telephone entry system according to claim 1, is characterized in that, also comprises and micro-controlThe key dial-up circuit that device processed is connected, stores in a key dial module corresponding in memoryCall number.