JP2779686B2 - Dial pulse recognition method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION INDUSTRIAL APPLICATION The present invention relates to a telephone line connected to a call path,
The present invention relates to a dial pulse recognition method for determining a dial pulse transmitted from a partner terminal.

[Conventional technology]

A dial signal sent to a line by an analog telephone terminal that is currently widely used is either a dial pulse signal or a push button signal. These dial signals are often sent to an exchange to which each terminal is connected for the purpose of setting a communication path from a state where a communication path has not been set.

However, in recent years, for the purpose of command code input to a center service represented by train seat reservation, remote control of an answering machine, etc., a dial signal is transmitted and received between terminals via the call path after the call path is set. Is increasing.

However, at present, the types of dial signals exchanged via a communication path are almost limited to push button signals. For this reason, a telephone user who can transmit only a dial pulse signal cannot use functions such as various center-based services and remote control of an answering machine.

Some terminals can send both dial pulse signals and push button signals, but if the connected exchange accepts only dial pulses, the type of dial signal sent before and after the call path is set Must be switched, which causes trouble for the telephone user.

Therefore, an apparatus for recognizing the number of transmitted dial pulses from a dial pulse signal received via a communication path has been developed.

By the way, the dial pulse is approximately a rectangular wave when observed on the line connected to the telephone that sent the pulse, but when transmitted via the communication path, distortion occurs due to the characteristics of the telephone transmission system. . In particular, the characteristic that the telephone transmission system does not transmit the DC component of the signal has a great effect, and the dial pulse waveform obtained on the receiving side via the communication path is almost as shown in FIG. 2 (b). If the second
If the waveform shown in Fig. (B) is always obtained,
The receiving side can recognize the transmitted dial signal by counting the number of pulses of the obtained signal.

However, since the telephone transmission system has various non-linearities in addition to the characteristic of cutting the DC component, a ringing phenomenon occurs as shown in FIG. 2 (c). This ringing phenomenon occurs due to the influence of the characteristics of the communication path as a coil and the characteristics of the capacitance, and the observed reception waveform causes damped oscillation. When the ringing phenomenon occurs, the number of pulses observed on the receiving side increases as compared to the case where this phenomenon does not occur. In this case, if the receiving side simply counts the number of pulses and obtains the transmitted dial number, a difference occurs between the dial number and the actually transmitted dial number.
Correction is required when calculating the transmission dial number from the number of reception pulses.

Specifically, the dial pulse observation waveform on the receiving side corresponding to a single transmission pulse is stored in advance as data, and at the time of actual reception, the stored waveform data is compared with the received waveform to be sufficiently similar. Is confirmed, it is considered that one pulse has been received at that time.

[Problems to be Solved by the Invention] However, as described above, a user of a telephone capable of transmitting only a dial pulse signal cannot use functions such as various center-based services and remote control of an answering machine, Also, terminal users who can send both dial pulse signals and push button signals must switch the dial signal type before and after the call path is set if the exchange connected only accepts dial pulses. There was a problem that it had to be done.

Also, since the characteristics of the communication path are not uniform, it is difficult to predict the degree of ringing and whether or not ringing has occurred, and the dialing waveform on the transmitting side varies depending on the dial transmitting circuit characteristics of the telephone device used for pulse transmission. I do. Therefore, when it is necessary to accurately recognize the number of dial pulses under various communication conditions, the number of dial pulse observation waveform data stored in advance becomes very large, and there is a problem that the cost is increased. Was.

An object of the present invention is to provide an inexpensive dial pulse recognition method that has high dial pulse determination accuracy and eliminates the above problems.

[Means for solving the problem]

The present invention solves the above-described problems, and as described above, the reception waveform of the transmission dial pulse varies depending on the characteristics of the telephone path transmission system and factors such as differences in the type of telephone device used for transmission. , The transmitted dial pulse can be received without fail.

Although the reception waveform of the transmission dial pulse changes variously as described above, the time interval from the start of the reception of the dial pulse to the end thereof is not affected by the above factors, and coincides with the dial transmission time on the transmission side. I do.

Therefore, means for detecting the arrival of the dial pulse signal is provided, the time interval from the start of the dial pulse signal reception to the end of the reception is measured, and the dial number is calculated from the time interval.

The arrival of the dial pulse signal is detected by the method described below.

When the transmission dial pulse shown in FIG. 2 (a) is received via the communication path transmission system, if there is no nonlinear distortion in the transmission system, the dial pulse falls as shown in FIG. 2 (b). Only a thin pulse arrives at each rising edge, but when there is nonlinear distortion in the transmission system, an attenuated oscillation wave is generated at each falling and rising edge of the dial pulse, and many pulses with a narrow time width are received at the receiving side. To come. The number of appearances and the time width of the arriving pulse vary depending on the characteristics of the communication path as described above.

Therefore, in order to reliably detect the incoming pulse, it is necessary to monitor the received waveform by high-speed sampling.

On the other hand, by providing an envelope extracting means and equivalently widening the time width of the arriving pulse, the arriving pulse can be confirmed without fail even if the sampling speed of the received waveform monitoring is reduced. FIG. 3 is a diagram schematically showing a transmission dial pulse waveform, a reception waveform, and an envelope waveform of the reception waveform.

Next, the envelope level at the maximum point of the envelope waveform extracted by the envelope extraction means is the maximum level at or above the first level threshold Vth1, and the envelope level at the minimum point of the extracted envelope waveform is the second level. 2 and a minimum point equal to or lower than the level threshold value Vth2.
The appearance of the maximum point and the minimum point is detected by the occurrence of the sign change of the difference between the envelope waveforms. Here, the relationship Vth1> Vth2 (1) is established between the level thresholds Vth1 and Vth2. FIG. 3 (c) shows the level threshold Vt.
Typical examples of h1 and Vth2 are shown. As shown in FIG. 3 (c), in the envelope waveform at the time of receiving the dial pulse, the level where the level is equal to or higher than the first threshold value Vth1 and the level where the level is the second threshold value are Vth1.
The minimum points below Vth2 come alternately. Furthermore, the appearance cycle of these maximum points is determined by the dial pulse transmission cycle (10 pps
100 mses for 20 pps and 50 msec for 20 pps). When the ringing described above occurs with a large amplitude, the appearance cycle is further shortened. Similarly, the appearance cycle of the minimum point satisfying the above condition is also shorter than the transmission cycle of the dial pulse.

The arrival of the dial pulse signal can be detected by checking the appearance pattern of the maximum point and the minimum point along the time series. For this purpose, three types of timers capable of independently resetting the count value are provided. When a maximum point satisfying the above condition is detected for the first time after the measurement is started, all three types of timers are reset and counting is started (point A in FIG. 3 (c)). Thereafter, the minimum points satisfying the above conditions (B1, B2 to B5 in FIG. 3 (c))
Each time a point is detected, the count value of the timer 1 is reset, and the maximum point (see FIG.
Each time C1, C2 to C5) are detected, the count value of the timer 2 is reset. By this operation, the timer 1 measures the appearance interval of the minimum point, and the timer 2 measures the appearance interval of the maximum point.

The count value of timer 1 and timer 2 is always time threshold Tt
Compare with h. Here, the time threshold value Tth is a value shorter than the transmission cycle of the dial pulse, and generally may be about the break time length of the dial pulse (TB in FIG. 3C). When the count value of timer 1 or timer 2 is equal to Tth
When it becomes larger, the appearance timing of the minimum point or the maximum point is different from that at the time of receiving the dial pulse signal, so that it is determined that the reception of the dial pulse signal has been completed (point D in FIG. 3 (c)).

The above is the method of detecting the arrival of the dial pulse signal.

The count value Tt3 of the timer 3 when the count value of the timer 1 or the timer 2 exceeds Tth is equal to a value obtained by adding the value of Tth to a time interval from the start to the end of the reception of the dial pulse signal. Therefore, the transmission cycle S of the dial pulse, which is a known value, and the make rate M of the transmission dial,
And the number N of dial pulses transmitted and the count value Tt3 of the timer 3, the relationship shown in equation (2) holds.

Tt3−Tth = (N−1) · S + (1−M) · S (2) ∴N = (Tt3−Tth) / S + M (2 ′) where N: number of dial palaces transmitted S: dial pulse transmission Period SM: Make rate of dial pulse to be transmitted Tt3: Count value of timer 3 When it is determined that reception of the dial pulse signal has been completed, the number of dial pulses can be obtained according to equation (2 '). However, the make ratio M has a specified value and is known. Further, the transmission period S of the dial pulse differs between the case where the transmission speed is 20 pps and the case where the transmission speed is 10 pps, but becomes a known value if the transmission speed is predetermined.

According to the equation (2 '), the dial pulse number N which should be a natural number may not be so. The value of (Tt3−Tth) is often longer than the time interval from the start to the end of the reception of the actual dial pulse signal due to the effects of ringing and the like described above. Let the value be the number N of dial pulses.

By the way, in addition to the dial pulse signal, a voice signal also comes to the line via the communication path due to the utterance of the other party. When an audio signal arrives, the envelope level rises and then drops to the original level after a high level persists while the other party continues to utter. High level duration
T1 corresponds to the time of occurrence of one or more syllables.
Syllable duration is 70-200 msec and average value is 130 msec [Saito et al .: "Basics of Speech Information Processing" (Showa 56-10) Ohmsha P.4
1]. At this time, the appearance interval of the maximum point and the minimum point appearing in the envelope waveform is equal to or longer than the duration of the syllable. In this case, the count value of the timer 1 or the timer 2 is equal to or longer than the time threshold Tth without being reset. Therefore, the voice signal resulting from the speech of the other party is not mistaken as the dial pulse signal.

[Action]

Since the present invention is configured as described above, if there is non-linear distortion in the transmission system of the communication path, the transmitted dial pulse becomes an attenuated vibration wave, which is difficult to identify, but the envelope extracting means provided on the receiving side. After the half-wave rectification of the damped oscillation wave, the envelope is extracted by passing through a low-pass filter, and the maximum point and the minimum point of the envelope are detected by a controller, and three timers are controlled. The time length of the transmitted dial pulse is measured, the number of transmitted dial pulses is calculated from the time length, and the number of the pulses can be recognized.

〔Example〕

FIG. 1A is a block diagram of one embodiment of the present invention, and FIG. 1B is a circuit diagram of one embodiment of the envelope waveform extracting unit 1.

In FIG. 1, reference numeral 1 denotes an envelope waveform extractor for extracting an envelope waveform of a dial pulse input via a line, 2 denotes a control unit, 3 denotes a first timer, 4 denotes a second timer, and 5 denotes a Each of the timers 3 is reset by a timer count reset signal from the control unit 2 and automatically counts time from zero. Reference numeral 6 denotes a display for displaying the recognized dial number value.

Further, in FIG. 1 (b), R1-R6 are resistors, C ₁ is a capacitor, D1, D2 are diodes, OP1, OP2 is an operational amplifier, 7 is an A / D converter.

In the embodiment shown in FIG. 1B, a half-wave rectifier circuit is formed by the operation amplifier OP1 and the diodes D1 and D2 around the operation amplifier OP1, and a low-pass filter is formed by the operation amplifier OP2, the capacitor C1 around the operation amplifier OP2, and the resistor R6. Make up,
The cutoff frequency is 20-30H. At this time, the output of the operation amplifier OP2 becomes the envelope of the input signal. This envelope is converted into a digital signal by the A / D converter 7 and taken into the control unit 2 at a constant period.
About 10 msec is desirable. Note that this embodiment shows a specific example, and it goes without saying that other realization means may be used.

FIG. 4 is a flowchart showing the operation of the embodiment of FIG. 1 (a).

Hereinafter, the operation of this embodiment will be described with reference to FIG.

The control unit 2 reads the envelope waveform level from the A / D converter 7 and calculates the difference value. Difference value D _n at time n is determined in accordance with the read value V _n and a value V _n -1 which will be read in one sampling period before the A / D converter 7 (3) at the same time.

_{D n = V n -V n -1} (3) where, Dn-1> 0 and D _n ≦ 0, when the hold (4), the envelope waveform takes a maximum point at time n-1, the level at that time Is V _n -1. Therefore, comparing V _n -1 and the first level threshold Vth1. Here, the first level threshold value Vth1 is a value stored in the control unit 2 in advance. When the relationship of V _n −1 ≧ Vth 1 (5) holds between V _n −1 and Vth 1, the control unit 2 controls the first timer 3, the second timer 4, and the third timer 5 Reset.

Thereafter, the control unit 2 detects a minimum point. The existence of the minimum point is detected when D _n −1 <0 and D _n ≧ 0, (6) hold for the difference value, and the level at that time is V _n −
It is one. Therefore, comparing V _n -1 and second level threshold Vth2. Here, the second level threshold Vth2 is also set in the control unit 2 in advance.
Is the value stored. When the relationship of V _n −1 ≦ Vth 2 (7) holds between V _n −1 and Vth 2, the control unit 2 resets only the first timer 3.

If it is detected that the expressions (4) and (5) hold simultaneously, only the second timer 4 is reset.

While detecting the local maximum point and the local minimum point, the control unit 2 stores the count value of the first timer 3 and the count value of the second timer 4 in the time threshold Tth stored in the control unit 2 in advance.
Then, it is confirmed whether or not the expression (8) is satisfied.

Tt1 ≧ Tth or Tt2 ≧ Tth (8) When the expression (8) holds, the count value of the third timer 5 is read, and the number N of dial pulses transmitted is calculated according to the expression (2 ′). The dial number is displayed on the display 6 according to the value.

Here, when N calculated according to the equation (2 ′) is not an integer, a value obtained by truncating the decimal part is displayed.
When N thus obtained is 0, it is determined that a voice is received instead of a dial pulse, and no display is performed. Further, when it is calculated that N = 10, the transmitted dial number is “0”, so “0” is displayed on the display 6, and when it is calculated that N = 1 to 9, N The value is displayed on the display 6.

〔The invention's effect〕

As described above in detail, according to the present invention, even if the reception dial pulse waveform is affected by the transmission system characteristics of the communication path and the difference in the telephone type of the transmitting telephone, the number of transmitted dial pulses can be accurately determined. And it can be realized at a lower cost than the conventional one.

Therefore, if a dial pulse recognition device using the present invention is installed, like a remote control signal of an answering machine,
As the various control signals after the communication path is set, an effect that dial pulses can be used on the transmission side can be expected.

[Brief description of the drawings]

FIG. 1 (a) is a block diagram of one embodiment of the present invention, FIG. 1 (b) is a circuit diagram of one embodiment of the envelope waveform extracting unit 1 of FIG. 1 (a), and FIG. 2 is a transmission dial. FIGS. 5A and 5B schematically show a pulse waveform and a reception waveform, wherein FIG. 5A shows a transmission dial pulse waveform, FIG. 5B shows a reception waveform when there is no nonlinear distortion in the communication path transmission system, and FIG. FIG. 3 is a diagram schematically showing a dial pulse waveform, a received waveform when the pulse is received through a communication path having nonlinear distortion, and its envelope waveform, and FIG. a) is a transmission dial pulse waveform, (b) is a reception waveform, (c) is an envelope of the reception waveform, and FIG. 4 is a flowchart showing the operation of the embodiment of FIG. 1 (a). 1 ... Envelope waveform extraction unit, 2 ... Control unit, 3 ...
1st timer, 4 ... second timer, 5 ... third timer, 6 ... display, 7 ... A / D converter

Claims (1)

(57) [Claims] A means for extracting an envelope waveform of a dial pulse signal arriving via a communication path; a controller for detecting an output of the extracting means; three timers controlled by the controller; And a display for displaying the recognition result of the controller, wherein the waveform level at the maximum point of the envelope waveform obtained by the control unit from the extraction means is the maximum dial point at which the first dial pulse detection threshold Vth1 or more. The minimum point where the waveform level at the minimum point of the envelope waveform is equal to or less than the second dial pulse detection threshold value Vth2 is detected.
Resetting the counts of the timers, resetting only the count value of the first timer when a subsequent minimum point is detected, and resetting only the count value of the second timer when detecting the maximum point, the first timer When the count value of the second timer or the count value of the second timer becomes equal to or greater than the time threshold value Tth, the dial pulse number is obtained and displayed from the count value of the third timer and the known dial pulse transmission cycle. Pulse recognition method.