JPH09107314A - Disable tone detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect a disable tone at a high success rate automatically by allowing a level monitor to calculate a level of an input signal, by outputting a level detection signal when the calculated value is higher than a threshold level and not outputting the detection signal when the calculated value is lower than the threshold level. SOLUTION: A 2.1kHz BPF device 2 applies band pass filtering processing to an input signal (i) to provide an output of a 2.1kHz band signal t21, and a level difference monitor 4 calculates a level difference dvt between a level vt of the 2.1kHz band signal t21 and a level nvt of a non 2.1kHz band signal nt21 based on timewise average between the 2.1kHz band signal t21 and the non 2.1kHz band signal nt21 being an output of a 2.1kHz band elimination filter 3. The monitor 4 provides an output of a 2.1kHz tone detection signal df by discriminating it that one of conditions of a disable tone that the frequency satisfies 2.1kHz when the level difference dvt is higher than a threshold level tdvt. On the other hand, when the level difference dvt is less than the threshold level tdvt, the monitor 4 does not provide an output of the 2.1kHz tone detection signal df.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a disable for automatically and efficiently detecting a disable tone for switching to a transparent mode without using an echo canceller or an echo suppressor in a communication network when performing data communication or the like. The present invention relates to a tone detection device.

[0002]

2. Description of the Related Art In a communication system, in order to transmit information from various transmission sources at high speed, flexibly and efficiently with the progress of multimedia, a conventional synchronous transfer mode (ST
In addition to M), the asynchronous transfer mode (ATM) is used.

This ATM requires a time for assembling and disassembling cells, which are the transfer units, and communication is delayed by this time. Originally, there are some echoes in the communication system, but if the communication delay time increases as described above, the echoes become apparent and the transmission quality due to the echo deteriorates. In order to eliminate this drawback, an echo canceller (echo canceller) is conventionally provided to reduce the echo by linear means when the telephone is accommodated in the ATM network.

By the way, if the echo canceller is operated during data transmission, a part of necessary data is lost. Therefore, when performing data communication, it is necessary to switch to a transparent mode in which the echo canceller is not operated. Disable tone is used to switch to mode. That is, if it is determined that the disable tone is detected, the mode is switched to the transparent mode.

In detecting the disable tone,
The frequency (2.1 kHz band), the level, and the phase inversion period of the input signal of either transmission or reception are monitored, and if all of them satisfy the specified values, the disable tone is detected. to decide. In addition, PL
A disable tone detecting device using L, a timer, etc. is disclosed in Japanese Patent Laid-Open No. 4-239824.

FIG. 2 is a diagram showing a conventional disable tone detecting device 200.

In the disable tone detecting device 200, the level monitoring device 1 calculates the level v of the input signal i from the time average of the input signal i, and the calculated level v is lower than the threshold value tv specified separately. If it is large, it is considered that the level, which is one of the conditions for the disable tone, is sufficient, and the level detection signal dl is output. is there. The level detection signal dl is continuously output while the level v is higher than the threshold value tv.

The 2.1 kHz band pass filtering device 2 is a device which performs band pass filtering on the input signal i and outputs a 2.1 kHz band signal t21.
The 2.1 kHz band elimination filtering apparatus 3 performs band elimination filter processing on the input signal i to obtain a non-2.1 kHz signal.
This is a device for outputting the Hz band signal nt21.

Further, the level difference monitoring device 4 is 2.1 kH.
2.1 kH output by the z band pass filtering device 2
The level vt of the 2.1 kHz band signal t21 and the non-2.1 kHz band signal according to each time average of the z band signal t21 and the non-2.1 kHz band signal nt21 output by the 2.1 kHz band elimination filtering device 3. nt21 level vn
and t, and the level difference dvt between the levels vt and vnt
If the calculated level difference dvt is larger than a separately designated threshold value tdvt, the 2.1 kHz tone detection signal df is output, and the level difference dvt is the threshold value tdv.
If t or less, the device does not output the 2.1 kHz tone detection signal df. The level difference dvt is equal to the threshold value td.
2.1 kHz tone detection signal df while larger than vt
Are output continuously.

The phase lock loop (PLL) 8 is a circuit for extracting the phase p of the input signal i, and the phase inversion detector 9 detects the phase inversion based on the discontinuity of the phase p output by the PLL 8. , A detection signal dpr indicating that the phase inversion has been detected is sent to the timer 10 at the time t.
This is a device that receives pr from the timer 10. In addition, the phase inversion detection device 9 uses the timer 10 at the time of immediately preceding phase inversion detection.
The time difference between the time tpr0 received from TPR0 and the time tpr is calculated, and if the calculated time difference is within the range of the separately specified time difference, it is determined that the phase inversion is properly performed in a predetermined cycle. Then, the number of phase inversions cpr is incremented by 1, and if the calculated time difference is outside the range of the specified time difference, it is determined that the phase inversion is not properly performed in the predetermined cycle, and In order to start counting from the beginning, the number of phase inversions cpr is cleared to 0.

When the number of times cpr of phase inversion exceeds the number of times tcpr specified separately, it is determined that the phase inversion is properly performed, and the phase inversion detection signal dr indicating that the appropriate phase inversion is detected is output. The phase inversion detection device 9 outputs, while the phase inversion number cpr is the designated number tcp.
If r is not exceeded, the phase inversion detection device 9 does not output the phase inversion detection signal dr.

Disable tone detection / determination device 71
Is the level detection signal dl output by the level monitoring device 1.
And the 2.1 kHz tone detection signal df output by the level difference monitoring device 4 and the phase inversion detection signal dr output by the phase inversion detection device 9. Then, the disable tone detection determination device 71 inputs the level detection signal dl indicating that the level v of the input signal i is larger than the specified threshold value tv, and further, the level vt of the 2.1 kHz band signal t21 and non-2. Threshold value td in which the level difference dvt from the level vnt of the 1 kHz band signal nt21 is specified
The disable tone is detected when the phase inversion detection signal dr indicating that the phase inversion is detected is input during the period in which the 2.1 kHz tone detection signal df indicating that it is larger than vt is input. Is a device which outputs the disable tone detection signal d indicating the above, and does not output the disable tone detection signal d when it is outside of the range.

[0013]

As described above, the conventional disable tone detecting apparatus 200 detects the disable tone by the operation including the phase extraction of the input signal by the PLL 8 and the phase inversion time measurement by the timer 10. It is a device for detecting.

However, in the conventional disable tone detecting apparatus 200, the phase of the PLL may fluctuate and the timer may be slightly desynchronized. In this case,
There is a problem that correct phase inversion detection cannot be performed.

Further, in the conventional disable tone detecting apparatus 200, since the PLL and the timer are used,
These PLLs and timers must be externally attached to the integrated circuit, and therefore the disable tone detection device 200
There is a problem that it is difficult to economically integrate these into a single integrated circuit.

Further, there is a problem that the mounting cost increases with the increase in the number of parts to be externally attached, and the cost of the echo canceller or the echo suppressor using the disable tone detecting device 200 also increases.

An object of the present invention is to provide a disable tone detecting apparatus which can detect a disable tone automatically and with high efficiency and which is economical.

[0018]

The present invention relates to a level monitoring device for outputting a level detection signal according to the level of an input signal, and a signal of 2.1 kHz band extracted from the input signal.
1 kHz band pass filtering device, 2.1 kHz band elimination filtering device for removing 2.1 kHz band signal from input signal, 2.1 kHz band signal and 2.1 kHz output by 2.1 kHz band pass filtering device
Non-2.1 kHz output by z-band elimination filtering device
A level difference monitoring device that outputs a 2.1 kHz tone detection signal according to the level difference from the z-band signal, detects the sign inversion of the input signal, calculates the sign inversion time, and based on the past sign inversion time. A phase for outputting a phase inversion detection signal by comparing the sign inversion time with the expected time of the code inversion, which is activated by the 2.1 kHz tone detection signal, and a sign inversion monitoring device for calculating the expected time of the code inversion. Inversion monitoring device, level detection signal and 2.1kHz
And a disable tone detection determination device that determines the disable tone detection based on the tone detection signal and the phase inversion detection signal.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a diagram showing a disable tone detecting apparatus 100 according to an embodiment of the present invention. The same parts as those in the disable tone detecting device 200 shown in FIG. 2 are designated by the same reference numerals.

The disable tone detecting apparatus 100 is
In the conventional disable tone detection device 200,
Instead of the PLL 8, the phase inversion detection device 9, and the timer 10, a code inversion monitoring device 5 and a phase inversion monitoring device 6 are provided.

The sign reversal monitoring device 5 detects the sign reversal of the input signal i, calculates the sign reversal time t, and also predicts the sign reversal time based on the past sign reversal times calculated before the sign reversal. This is a device for calculating tp.

The phase inversion monitoring device 6 is a device which is activated by the 2.1 kHz tone detection signal df and outputs the phase inversion detection signal dr by comparing the sign inversion time t and the expected time of sign inversion tp. is there.

Next, the operation of the above embodiment will be described.

First, the level monitoring device 1 calculates the level v of the input signal i from the time average of the input signal i. If the calculated level v is larger than a threshold value tv specified separately, the disable tone is generated. Assuming that the level, which is one of the conditions for
On the other hand, if the level v is equal to or lower than the threshold value tv, the level detection signal dl is not output. The level detection signal dl is continuously output while the level v is higher than the threshold value tv.

Then, the 2.1 kHz band pass filtering device 2 performs band pass filtering on the input signal i and outputs a 2.1 kHz band signal t21.
The kHz band elimination filtering device 3 performs band elimination filtering on the input signal i and outputs the non-2.1 kHz band signal nt21.

In addition, the 2.1 kHz band signal t21 output by the 2.1 kHz band pass filtering device 2 and 2.
According to each time average with the non-2.1 kHz band signal nt21 output by the 1 kHz band elimination filtering device 3,
The level difference monitoring device 4 controls the level vt of the 2.1 kHz band signal t21 and the level vt of the non-2.1 kHz band signal nt21.
nt and the level difference dv between the levels vt and vnt
If t is calculated and the calculated level difference dvt is larger than a separately designated threshold value tdvt, the frequency that is one of the conditions for being a disable tone is 2.1k.
The frequency difference dvt is equal to the threshold value tdvt, while the 2.1 kHz tone detection signal df is output assuming that the frequency is satisfied.
In the following cases, the 2.1 kHz tone detection signal df is not output. The 2.1 kHz tone detection signal df is continuously output while the level difference dvt is larger than the threshold value tdvt.

As described above, the level detection signal dl is output according to the level v of the input signal i, and the level vt of the 2.1 kHz band signal t21 and the non-2.1 kHz band signal nt2 are output.
2.1 according to the level difference dvt from the level vnt of 1.
The kHz tone detection signal df is output.

The sign inversion monitoring device 5 receives the input signal i, and receives the sign inversion time t and the expected code inversion time t.
p is calculated and output to the phase inversion monitoring device 6. That is, the sign inversion monitoring device 5 detects the sign inversion of the input signal i, interpolates the waveform to convert 2.1 kHz into the telephone system 8 kHz, and calculates the sign inversion time t after this waveform interpolation. Further, assuming that the past sign reversal times for the separately specified number not are t ₁ , t ₂ , t ₃ , ..., T _not , the sign reversal period pet is calculated based on the average of these intervals. The immediately preceding code inversion time t _not is added to the code inversion cycle pet calculated in this way to obtain the code inversion expected time tp. The sign inversion time t and the expected sign inversion time tp are output to the phase inversion monitoring device 6.

The phase inversion monitoring device 6 receives the code inversion time t input from the code inversion monitoring device 5 and the expected code inversion time tp.
Phase inversion is detected based on the result of comparison with and the phase inversion detection signal dr is output. That is, the phase inversion monitoring device 6 receives 2.1 kHz input from the level difference monitoring device 4.
It is activated by the tone detection signal df (operation starts when the 2.1 kHz tone detection signal df is input from the level difference monitoring device 4), and in order to start counting from this time, the code inversion number count cs and the phase inversion number Clear the count cp and 0.

Here, the separately specified minimum value of the code inversion number is ns _min , the separately specified maximum value of the code inversion number is ns _max , and the separately specified code inversion time allowable amounts are et1, et2, Let et3 and et4. And
The level difference monitoring device 4 displays the 2.1 kHz tone detection signal df
The phase inversion monitoring device 6 outputs the following
, Are repeatedly executed, and in the process, the phase inversion detection signal dr is output to the disable tone detection determination device 7.

When cs <ns _min . tp-
If et1 ≦ t ≦ tp + et2, the code inversion number count cs is incremented by 1. Otherwise, the code inversion number count cs and the phase inversion number count cp are cleared to 0.

When ns _min ≤ cs ≤ ns _max . If tp−et3 ≦ t ≦ tp + et4, the code inversion number count cs is incremented by 1. If not, the code inversion number count cs is cleared to 0 and the phase inversion number count cp is incremented by 1. Then, when the maximum value of the number of times of phase inversion specified separately is np, if np ≦ cp,
The phase inversion detection signal dr is output to the disable tone detection determination device 7, and if not, the phase inversion detection signal d
Do not output r.

When ns _max <cs. The sign inversion number count cs and the phase inversion number count cp are set to 0.
To clear.

Then, the disable tone detection / judgment device 7 makes judgment based on the level detection signal dl, the 2.1 kHz tone detection signal df and the phase inversion detection signal dr, that is, the level detection signals dl and 2.1 kHz. While the tone detection signal df is being received at the same time, the disable tone detection signal d is output only when the phase inversion detection signal dr is received.

According to the above embodiment, since the phase inversion can be detected without using a special device such as a PLL or a timer, it is not necessary to consider the phase fluctuation of the PLL itself, and the desynchronization of the timer may cause a loss of synchronization. It is not necessary to consider a malfunction, and for this reason, the disable tone detection can be automatically performed with high efficiency. Further, since no special external parts such as the PLL or the timer are used, the disable tone detecting device can be constructed economically.

Therefore, the disable tone detecting apparatus 100 for detecting the disable tone required when switching to the transparent mode for performing data communication,
When applied to an echo canceller or an echo suppressor (echo suppressor) in a communication network, an echo canceller or an echo suppressor that can perform disable tone detection automatically and with high efficiency can be economically realized. As a result, high quality voice and data can be economically transmitted in the age of multimedia communication.

The above embodiment performs the operation including the calculation of the sign inversion time of the input signal i and the expected code inversion time, and the phase inversion detection from the comparison between the calculated code inversion time and the expected code inversion time. It should be noted that, in the above embodiment, even if the way of including the equal sign of the magnitude determination in each procedure is changed,
The effect is the same.

[0038]

The present invention has the effect of being able to detect a disable tone automatically and with high efficiency, and being economical.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a disable tone detection device 100 according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a conventional disable tone detection device 200.

[Explanation of symbols]

1 ... Level monitoring device, 2 ... 2.1 kHz band pass filtering device, 3 ... 2.1 kHz band elimination filtering device, 4 ... Level difference monitoring device, 5 ... Sign reversal monitoring device, 6 ... Phase reversal monitoring device, 7 ... Disk Able tone detection / judgment device, i ... Input signal, t ... Sign reversal time, tp ... Expected sign reversal time, dr ... Phase reversal detection signal, v ... Level of input signal i, tv ... Threshold value, dl ... Level detection signal, t21 ... 2.1 kHz band signal, nt21 ... non-2.1 kHz band signal, vt ... level of 2.1 kHz band signal t21, vnt ... level of non-2.1 kHz band signal nt21, dvt ... level difference between levels vt and vnt, tdvt ... Threshold value, df ... 2.1 kHz tone detection signal, pet ... Sign inversion period, t _not ... Immediately preceding sign inversion time, cs ... Sign inversion time Number count, cp ... Phase inversion number count, ns _min ... Minimum value of code inversion number, ns _max ... Maximum value of code inversion number, et1, et2, et3, et4 ... Allowable amount of code inversion time, d ... Disable tone detection signal.

Claims (1)

[Claims] 1. A level monitoring device for outputting a level detection signal according to the level of an input signal;
2.1 kHz band pass filtering apparatus for extracting 1 kHz band signal; 2.1 kHz band elimination filtering apparatus for removing 2.1 kHz band signal from the input signal; 2 output by the 2.1 kHz band pass filtering apparatus A level difference monitoring device that outputs a 2.1 kHz tone detection signal according to a level difference between the 1 kHz band signal and the non-2.1 kHz band signal output by the 2.1 kHz band elimination filtering device; and a sign inversion of the input signal. And a sign reversal monitoring device that calculates the sign reversal time and calculates the expected time of the sign reversal based on the past sign reversal times; and the code activated by the 2.1 kHz tone detection signal. A phase inversion detection signal is output by comparing the inversion time with the expected time of the sign inversion. A phase inversion monitoring device; and a disable tone detection determining device for determining disable tone detection based on the level detection signal, the 2.1 kHz tone detection signal, and the phase inversion detection signal. Disable tone detector.