JPS60185452A - Optimum impedance deciding method of side tone preventing circuit - Google Patents

Abstract

PURPOSE:To decide an optimum impedance in a short time by providing a process changing a resistance value and obtaining an impedance giving a minimum side tone, and a process changing a reactance value and obtaining an impedance with a minimum side tone. CONSTITUTION:The reactance value of a variable impedance balancing circuit 6 is fixed and the resistance value is changed in a prescribed change width. The impedance value with a minimum B/C is fixed. Then the resistance value is fixed based on the value and the reactance is changed in a prescribed change width. The impedance is fixed with the minimum B/C. The process above is repeated further. The values of B/C and A/C are compared and when the B/C is small, a control section 13 supplies a switch signal to a switch section 16 via a signal line 15 to turn on a switch SW2 and turn off a switch SW1.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a method for determining the optimum impedance of a side sound protection circuit used in communication terminal equipment such as a telephone connected to a line.

[Technical background of the invention and its problems]

In conventional side sound prevention circuits, two variable impedance balanced circuit networks are used, one of which is connected to a communication path, and the impedance of the other is changed to change the side of the variable impedance balanced network connected to the communication path. A method in which the sidetone that is smaller than the sound is obtained, the variable impedance balanced circuit network with the reduced sidetone is connected to the communication path, and the same adjustment as above is made for the other variable impedance balanced circuit network, and this is repeated. was there.

However, this method requires two variable impedance balanced circuit networks, is complex in configuration and control, and has the drawback of high cost.

Therefore, one side is a fixed impedance balanced circuit network, and the other side is a variable impedance balanced circuit network. A method has been proposed in which a variable impedance balanced circuit network, which is controlled to have this impedance by sequentially changing the impedance value when the minimum sidetone is observed, is connected to the communication path. .

According to this method, the more points at which sidetone is observed by changing the impedance value of the variable impedance balanced network, the more the sidetone can be observed, even if there are so-called variations in the impedance conditions of the line network and the characteristics of the variable impedance balanced network. Although it can handle this, it took a lot of time to find the impedance that would produce the minimum sidetone.

Well, the fewer points you observe sidetone, the faster you can find the impedance when the sidetone is at its minimum.
This has the disadvantage that if the sidetone is small, the sound will be distorted.

[Purpose of the invention]

The present invention was made in view of the drawbacks of the conventional methods as explained above, and its purpose is to obtain the impedance that causes the minimum sidetone within a short h period without complicating the configuration. The object of the present invention is to provide a method for determining the optimal impedance of a potentially side-tone protection circuit.

[Summary of the invention]

Therefore, in the present invention, for the impedance of the variable impedance balanced circuit network of the side sound prevention circuit having the variable impedance balanced circuit network and the fixed impedance balanced circuit network, the reactance value is fixed and the resistance value is varied in a predetermined variation width. A first step of determining the impedance that produces the minimum sidetone by observing the sidetone at the impedance, and a sidetone generated at each impedance by changing the reactance value while fixing the resistance value of the impedance of the variable impedance balanced circuit network. This is a process that combines the second process of observing the minimum sidetone and calculating the impedance of the sound.
In addition, at least one process is performed multiple times, and in the process performed multiple times, the change width of the resistance value or reactance value of the subsequent process is equal to the change in the resistance value or reactance value of the previous process. By making it smaller than the width, the second objective was achieved.

[Embodiments of the invention]

Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram of a side sound protection circuit to which the method of the present invention is applied. In the figure, 1 indicates line impedance. The signal output from this line impedance 1 directly reaches one input terminal of each of the differential amplifiers 8.9. Further, a resistor 2 is connected to the line impedance 1, and a resistor 4 is connected between the resistor 2 and the other input terminal of the differential amplifier 8. Further, a resistor 3 is connected between the resistor 2 and the other input terminal of the differential amplifier 9.

A transmitting output circuit 5 is connected to the connection point between the resistor 2 and the resistor 3.4, and the other end of the transmitting output circuit 5 is grounded.

A fixed impedance balanced network 7 is connected between the input terminal of the differential amplifier 8 that is connected to the resistor 4 and the ground, and a fixed impedance balanced network 7 is connected between the input terminal of the differential amplifier 9 that is connected to the resistor 3 and the ground. A variable impedance balancing network 6 is connected therebetween.

Unfortunately, the output signals of the differential amplifiers 8 and 9 are transferred to the switch section 16.
The signal is sent to the communication path terminal 18 via the switches SWI and SW2. In the second configuration below, line impedance 1, resistors 2 and 4, fixed impedance balanced circuit network 7,
The differential amplifier 8 constitutes a bridge circuit, and the line impedance 1, the resistors 2 and 3, the variable impedance balanced circuit network 6, and the differential amplifier 9 constitute another bridge circuit.

Furthermore, the control unit 13 controls the output signal of the differential amplifier 8.9 to
The output signal from the transmitter output circuit 5 is input through the signal line 12, respectively. Here, if the input from the signal line 10 is A1, the input from the signal line 11 is B1, and the input from signal 1vil12 is C, the control unit 13 calculates A/C and B/C, respectively, and stores them. . Although there are analog approximation methods for this division, here, for the sake of simplicity, it is assumed that the input is converted into a digital value and the calculation is performed by the processor. Further, the control unit 13 sends a signal to the variable impedance balancing circuit network 6 via the signal line 14 to control the impedance value to a predetermined value. The control unit 13 calculates B/C for 4B whose impedance is changed by this control, and stores the entire value. These B/C
, A/C are considered to be side sound attenuators, so by comparing them, a side sound prevention circuit with the optimum impedance at the minimum is realized.

Furthermore, during the above operation, the control section 3 sends a switching signal from the signal line 15 to turn on (close) the switch SW1 of the switch section 16 and turn off (open) the switch SWQ.

In the above operation, how the control unit 13 determines the optimal impedance will be specifically described. That is, it is assumed that the complex impedance plane realized by the variable impedance balanced circuit network 6 is as shown in FIG. Then, in order to observe which of the impedance values indicated by the intersections of the broken lines on the impedance complex plane produces the minimum sidetone, the control unit 13 changes the resistance value and fixes the actance value, and Realize the impedance of the intersection. Now, in the initial state, if the impedance value of the variable impedance balancing circuit network 6 is a value represented by (Ro, Xo), then the reactance value is X.

is fixed, and the resistance value R8 is varied by a variation width indicated by Wlo. Here, the impedance value is (R1°Xo)
If B/C is the minimum at the value shown by
Based on the impedance value at this time, the resistance value R1 is fixed, and the reactance value Xo is varied by a variation width indicated by W. It is assumed that among the B/Cs obtained by this change, the B/C when the impedance value is a value represented by (R1, Xi) is the minimum. Next, based on the above impedance value (R□, X,), reactance value X1
is fixed, and the resistance value R1 is varied by a variation width indicated by WB9. Here, WB2<WRl is established. In addition, the impedance value at which the sidetone is minimum is the resistance value WRI centered on the impedance value (R1, Xl).
/2, so in this embodiment, the resistance value is changed within this region (the quadrupled region indicated by the broken line).

As a result, it is assumed that B/C is the minimum when the impedance value is represented by (Rs, Xt). Next,
Based on the impedance value (R9, Xt).

Fix the resistance value R3 and set the reactance value to W. Change by the change range shown by . In this case as well, yellow,
o, As a result of changing the impedance value in this way and calculating B/C, if the B/C is the minimum when the impedance value is (Rt, Xs), then the B/C at this time and the Compare the installed A/C. As a result, if B/C is small, the control section 13 gives a switching signal to the switch section 16 via the signal line 15, turns on the switch SW2, and turns off the switch SWI.
! :do. Further, when the A/C is small, the switch section 16 is left as is, and the fixed impedance balanced circuit network 7
Select.

An example of the variable impedance balanced circuit network 6 is a six-element circuit as shown in FIG. This circuit consists of variable resistors 42, 43, 'OT variable capacitor = 14
, 45, a fixed resistor 46, and a fixed capacitor 47, the terminal 48 is connected to the resistor 3 shown in FIG. 1, the terminal 49 is grounded, and the terminals 50 and 51 are
A signal line 14 extending from the control section 13 is connected.

The control section 13 receives a signal from the terminal 50 to change the resistance value, and receives a signal from the terminal 51 to change the reactance value. As a result, the variable resistors 42 and 43 change while maintaining the same resistance value, and the variable capacitors 44 and 45 change while maintaining the same reactance, thereby realizing the first and second steps as in the embodiment.

FIG. 4 shows the flowchart 1 of the method of the embodiment of the present invention.
It is shown as closed.

That is, the operation starts, and in step 101, the fixed impedance balanced circuit network 7 is connected to the communication path. After this,
In step 102, it is determined whether or not sampling processing is in progress. If sampling processing is in progress, A/C and B/C are taken in in step 103.

Thereafter, in step 104, the requested A, /C,
For B/C, when the sidetone becomes small, step 10
5, the impedance value at that time is stored. Of course, as explained in Fig. 2, you can vary the resistance value or actance value by -000 degrees to determine B/C, then compare it and memorize the impedance value that yields the minimum sidetone. good.

Next, the process proceeds to step 106, where it is determined whether the variable impedance balancing circuit network 6 has been changed a predetermined number of times. That is, in the example shown in FIG. 2, the total number of times the resistance value is changed in the first and third times and the reactance value is changed in the second and fourth times is stored in advance in the control unit 13. It is determined whether it is set and the number of times has reached this value.

If NO in step 106, it is determined in step 107 whether to change the resistance value or the reactance value, and if the resistance value is to be changed, the change width 'wR1 is set. This step 107,
Step 108 is performed by predetermining in advance how many times and by what change width the resistance value is to be changed in the first time. When the change width WRi is set in step 108, the process proceeds to step 109, and the value to be reached by changing the resistance value of the variable impedance balancing circuit network 6 in the control section 13 is determined. Thereafter, in step 110, the variable impedance balancing network 6 is controlled by the signal line 14, and the process returns to step 102. Further, in steps 111 and 112, the case where the reactance value of the variable impedance balancing circuit network 6 is changed is shown. In this case as well, it is assumed that in the first time, it is determined how many times and by what range of change the reactance value is to be changed.

Even when the reactance value is changed in this manner, the variable impedance balancing network 6 is controlled by the signal line 14 in step 110, and the process returns to step 102.

When the impedance value has changed a predetermined number of times in this manner, the process branches to YES in step 10G and proceeds to step 113. In Stesoge 113, B/C and A/
It is determined whether the fixed impedance balanced circuit network 7 is optimal or not by comparing it with C. If YES, the state in which the fixed impedance balanced circuit network 7 is connected to the communication path is maintained in step 114. Further, if NO in step 113, the control unit 13 controls the variable impedance balancing circuit network 6 via the signal line 14 in step 115 so that the impedance value becomes the minimum B/C, Further, the process proceeds to step 116, where the variable impedance balance network 6
Connect to the communication path.

In this way, the combination of the first step of changing the resistance value and the second step of changing the reactance value includes the first and second steps twice each. As shown in the figure, the optimum impedance can be determined by changing it 15 times. That is, 1+(Ml-1)+(Nl-1)+
(N2-1)+(N2-1)=M1+N1+M2+
2-3 Here, M1=4, N1=4, N2-5, N2=5.

In comparison, the conventional method requires a total of 256 changes. That is, (N1+(Ml-1)(N2-1)l (N1+(Nl
-1) (N2-1) )=(Ml・N2-N2+
1)+(Nl·N2-N2+1) Here, N1=4, N1=4, N2-5, N2=5.

In the above embodiments, the first step and the second step were performed alternately, but they do not necessarily have to be performed alternately. In the first or second step, which is performed multiple times, there is no limit to the area that can be changed and observed in the later steps, but in order to reduce the total number of changes, it is necessary to It is preferable to set the region before and after 172 of the change width of the process as the region to change, or to make the region to change between the impedance value before and after the impedance value determined in the previous step.

In addition, in order to accurately measure sidetone, sampling of outputs A and B is performed when output C is present (generally, when output C is at a level slightly higher than the received signal level). ).

〔Effect of the invention〕

As described above, according to the present invention, it is possible to determine an impedance value that can achieve the minimum sidetone in a short time (number of changes). Furthermore, since variable and fixed impedance balancing networks are used, complexity and high cost of construction can be eliminated.

Furthermore, since the variable impedance balanced circuit network is configured to control impedance separately into resistance value and actance value, the method of the present invention is suitable for actual control. It's convenient.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a side sound prevention circuit to which the method of the present invention is applied, FIG. 2 is a diagram showing an impedance complex plane of impedance determined by an embodiment of the present invention, and FIG. 3 is a variable impedance balance A circuit diagram of the circuitry, FIG. 4, is a flowchart of one embodiment of the present invention. 5... Sending output circuit 6... Variable impedance balanced circuit network 7... Fixed impedance balanced circuit network 8.9... Differential amplifier 13... Control section 16... Switch section agent Patent attorney Author: Hiroshi Yoshi, Asahigaokano Factory, Hino City0 Author: Takeshi Horiuchi, Asahigaokano Factory, Hino City

Claims (4)

[Claims] (1) A variable impedance balanced circuit network, a fixed impedance balanced circuit network, a bridge circuit connected to each circuit network, and a control section that controls the circuit network, and the control section controls the variable impedance balanced circuit network. In the method of determining the optimal impedance by changing the impedance of the variable impedance balanced network, the reactance value is fixed and the resistance value is varied within a predetermined variation range to obtain the sidetone at each impedance. The first step is to observe the impedance of the variable impedance balanced circuit network to find the impedance that produces the minimum sidetone, and to observe the sidetone at each impedance by changing the reactance value while keeping the resistance value fixed for the impedance of the variable impedance balanced circuit network, and to find the minimum sidetone. It is a combination of a second step of calculating the impedance associated with sound, and consists of a combination step that includes at least one step multiple times, and in the step that is performed multiple times, the change width in the subsequent step is A method for determining the optimum impedance of a side sound protection circuit whose characteristic is to be smaller than the variation width of the process being performed. (2) In the subsequent process, the impedance is changed between the impedance before and after the impedance determined in the previous process. How to determine the optimal impedance of the sidetone circuit. (3) In the process to be performed later, the impedance is changed in a region around the impedance value of 172 of the change width in the previous process with the impedance determined in the previous process as the center. A method for determining the optimum impedance in a side sound protection circuit according to claim 1, characterized in that: (4) Optimal in the side sound protection circuit according to any one of claims (1) to (3), characterized in that the first step and the second step are performed repeatedly and alternately. Impedance determination method.