TWI390948B - A phone and a method for subscriber line interface circuit to reduce noise - Google Patents

Description

Method for reducing interference by telephone set and user line interface circuit thereof

The present invention relates to a telephone, and more particularly to a subscriber line interface circuit for a telephone.

The role of the Subscriber Line Interface Circuit (SLIC) is to implement the connection between various subscriber lines and switches. However, when multiple users use the same subscriber line interface circuit together, certain crosstalk interference will occur.

Take Japan Telecom as an example. Referring to Figure 4, when the phone is on hook, the voltage difference between the tip wire and the ring wire needs to be maintained at 48V. According to the characteristics of the subscriber line interface circuit, when the telephone is on-hook, a constant voltage mode is adopted, and the voltage difference is generally set to 48V. When the phone is in the off hook state, the current constant mode is used, and is generally set to 22 mA. When the telephone is in the pulse dialing state, the end line and the loop line will generate an oscillating voltage, that is, since the telephone line is in the pulse dialing state, the end line and the loop line will alternate between a voltage constant mode and a current constant mode, and a voltage is generated. The situation of shocks. Therefore, when the telephone is in the pulse dialing state, it will cause cross talk to the adjacent telephone, thereby affecting the call effect.

How to eliminate the crosstalk interference generated by the telephone to the adjacent telephone during the call becomes an urgent problem to be solved by the subscriber line interface circuit.

In view of this, it is necessary to provide a subscriber line interface circuit (Subscriber Line Interface Circuit (SLIC) A method of reducing interference used to reduce crosstalk between adjacent telephones.

In addition, there is a need to provide a telephone for reducing crosstalk interference between adjacent telephones.

The method for reducing interference by the subscriber line interface circuit provided in the embodiment of the present invention is applied to a telephone, and the telephone includes a monitoring module, a control module and a temporary register. The method comprises the following steps: the monitoring module monitors the working state of the telephone, including the on-hook state, the off-hook state and the pulse dialing state; when the monitored telephone enters the on-hook state, the register reads the end line while on-hook state The voltage value; when the telephone is monitored to enter the off-hook state, the register reads the voltage value of the end line and the loop line when the off-hook state is respectively; when monitoring the telephone to enter the pulse dialing state, the control module reads the temporary storage. The voltage value in the device is calculated and the common voltage value is output to the loop line, so that the waveform of the oscillating voltage generated by the loop line and the end line is symmetrical and opposite in phase.

The telephone provided in the embodiment of the present invention comprises a subscriber line interface circuit, wherein the subscriber line interface circuit comprises a monitoring module, a temporary register and a control module. The monitoring module is configured to monitor the working state of the telephone according to the subscriber line signal, including the on-hook state, the off-hook state and the pulse dialing state; the register is connected to the subscriber telephone line by the end line and the loop, for reading and storing. The voltage value of the line and loop in the off-hook state and the on-hook state; the control module is configured to receive the monitoring result of the monitoring module, read the voltage value in the register, calculate the common voltage value, and output the loop line in the pulse dialing state The oscillating voltage waveform generated by the loop line and the end line is symmetrical and opposite in phase.

The detailed description of the specific embodiments and the accompanying drawings will be The above contents and the technical effects of the invention are easily understood.

1 is a block diagram of a Subscriber Line Interface Circuit (SLIC) 10 and an application environment thereof according to an embodiment of the present invention. The subscriber line interface circuit 10 is disposed in the telephone 30 and is coupled to the subscriber telephone line 20 by an end line 41 and a loop 42. The subscriber line interface circuit 10 includes a monitoring module 100, a register 200 and a control module 300.

The monitoring module 100 is configured to monitor the operating state of the telephone 30 based on the subscriber line signal. The subscriber line signal includes subscriber line signals such as on hook, off hook, and pulse dialing. The working state of the telephone 30 includes an on-hook state, an off-hook state, and a pulse dialing state.

The register 200 is connected to the subscriber telephone line 20 by a tip wire 41 and a ring wire 42 for reading and storing the voltage values of the end line 41 and the loop line 42 in the on-hook state and the off-hook state. .

The control module 300 is configured to receive the monitoring result of the monitoring module 100, read the voltage value in the register 200, and calculate the common voltage value to be output to the loop 42 in the pulse dialing state.

Please refer to FIG. 2 , which is a flowchart of a method for reducing interference by the subscriber line interface circuit 10 in the embodiment of the present invention. In step S100, the monitoring module 100 monitors the working state of the subscriber line. In the present embodiment, the monitoring module 100 is configured to monitor the operating state of the telephone 30 based on the subscriber line signal. When the monitoring module 100 detects the on-hook signal, the telephone 30 enters the on-hook state, and then controls The module 300 performs step S200. When the monitoring module 100 detects the off-hook signal and the telephone 30 enters the off-hook state, the control module 300 performs step S300. When the monitoring module 100 detects the dial pulse signal, the telephone 30 enters the pulse dialing state, and the control module 300 performs step S400.

In step S200, when the telephone 30 enters the on-hook state, the register 200 reads and stores the voltage value V1 of the end line 41 in the on-hook state. For example, the end line 41 is on-hook with a state voltage V1 = -4V.

In step S300, when the telephone 30 enters the off-hook state, the register 200 reads and stores the voltage values V2, V3 when the end line 41 and the loop line 42 are in the off-hook state, respectively. For example, the voltage V2 of the end line 41 in the off-hook state is -14 V, and the voltage of the loop line 42 in the off-hook state is V3 = -37 V.

In the present embodiment, the impedance of the telephone 30 changes with the transition between the on-hook state and the off-hook state. When the on-hook state is off-hook, the voltage of the end line 41 of the telephone is lowered, and the voltage of the loop 42 is raised. However, the voltage rise and fall of the end line 41 and the loop 42 are generally different.

In step S400, the control module 300 reads the voltage values V1, V2, and V3 in the register 200, and calculates the common voltage value V4 to be output to the loop 42 in the pulse dialing state, so that the end line 41 and the loop 42 are oscillated. The voltage waveform is symmetrical and the phases are opposite.

In the present embodiment, the oscillating voltage refers to a voltage that is oscillated up and down due to the occurrence of the up-and-down line 41 and the loop line 42 when the telephone 30 is in the pulse dialing state. In the present embodiment, the peak value of the oscillation voltage of the end line 41 is the voltage value V1 at the on-hook state, the valley value is the voltage value V2 at the off-hook state, and the peak value of the oscillation voltage of the loop 42 is the off-hook state. Voltage value V3, the trough value Common voltage value V4.

In the present embodiment, the calculation formula of the common voltage value V4 outputted to the loop 42 by the control module 300 is: the common voltage value V4=V1-(V2-V3)-(V1-V2)x2.

That is, V4-V3=V2-V1. In the present embodiment, since the voltage difference between the end line 41 and the loop line 42 is equal in the pulse dialing state, the waveform of the oscillating voltage is symmetrical and the phases are opposite, so that the noise generated by the electromagnetic effect can be reduced, that is, Crosstalk interference to the telephone 30 of an adjacent circuit can be reduced.

Referring to FIG. 3, a voltage change diagram in three states in the application of the method for reducing interference of the subscriber line interface circuit 10 in the embodiment of the present invention. As can be seen from the figure, in the present embodiment, when the telephone 30 enters the pulse dialing state, the generated oscillating voltage waveform is symmetrical and opposite in phase, so that the noise generated by the electromagnetic effect can be changed, that is, the adjacent pair can be reduced. The telephone 30 of the circuit produces crosstalk interference.

In summary, the present invention complies with the requirements of the invention patent and submits a patent application according to law. The above description is only the preferred embodiment of the present invention, and equivalent modifications or variations made by those skilled in the art will be included in the following claims.

20‧‧‧User telephone line

30‧‧‧ telephone

41‧‧‧End line

42‧‧‧Circle

10‧‧‧User Line Interface Circuit

100‧‧‧Monitor module

200‧‧‧ register

300‧‧‧Control Module

1 is a block diagram of a subscriber line interface circuit and an application environment thereof according to an embodiment of the present invention.

2 is a flow chart of a method for reducing interference by a subscriber line interface circuit in an embodiment of the present invention.

3 is a diagram showing voltage changes in three states in a method for reducing interference of a subscriber line interface circuit in an embodiment of the present invention.

4 is a graph showing voltage changes in three states of the subscriber line interface circuit in the background art.

Claims (4)

A method for reducing interference by a subscriber line interface circuit is applied to a telephone, the telephone includes a monitoring module, a control module and a temporary register, the method comprising the following steps: the monitoring module monitors the working state of the telephone, including hanging up State, off-hook state, and pulse dialing state; when the phone is monitored to enter the on-hook state, the register reads the voltage value of the end line in the on-hook state; when the phone is monitored to enter the off-hook state The buffer reads the voltage value of the end line and the loop line in the off-hook state respectively; and when monitoring the telephone to enter the pulse dialing state, the control module reads the voltage value in the register and The common voltage value is calculated and output to the loop, so that the loop line and the end line generate an oscillating voltage waveform that is symmetrical and opposite in phase. The method for reducing interference by a subscriber line interface circuit according to claim 1, wherein the common voltage value is calculated as: a voltage value of the end line in the on-hook state - (the end line is at the off-hook The voltage value in the state - the voltage value of the loop line in the off-hook state) - (the voltage of the end line in the on-hook state - the voltage of the end line in the off-hook state) x 2 . A telephone line includes a subscriber line interface circuit, and the subscriber line interface circuit includes: a monitoring module, configured to monitor a working state of the telephone according to the subscriber line signal, including an on-hook state, an off-hook state, and a pulse dialing state; and a temporary register The end line and the loop line are connected to the user telephone line for reading and storing the voltage values of the end line and the loop line in the off-hook state and the on-hook state; the control module is configured to receive the monitoring result of the monitoring module, and read the temporary In the memory The voltage value is calculated and output to the loop line in the pulse dialing state, so that the loop line and the end line generate an oscillating voltage waveform that is symmetrical and opposite in phase. The telephone set according to claim 3, wherein the common voltage value is calculated as: a voltage value of the end line in the on-hook state - (a voltage value of the end line in the off-hook state - the loop line The voltage value at the off-hook state) - (the voltage at which the end line is in the on-hook state - the voltage at which the end line is in the off-hook state) x 2 .