JPH01198891A - Dial pulse detecting system - Google Patents

Abstract

PURPOSE:To accurately detect a dial pulse under a telephone call by obtaining a position for the make/break of the dial pulse as the one at which the correlation between a step response and an input signal is large. CONSTITUTION:An input signal X is analyzed at an analyzing part 31, a coefficient A of a synthesizing filter 2 is obtained, a step response R is obtained at a step response part 32, and a cross-correlation phixr between the input signal X and the step response R is obtained at a cross-correlation part 33. Further, an auto-correlation phirr of the step response R is obtained at an auto-correlation part 34. The cross-correlation phixr is made into the initial value of an evaluation function, a first step is placed at the position where the absolute value of the evaluation function is the maximum, and a result obtained by subtracting the auto-correlation, which is normalized to be as large as the step at the position where the step is placed, from the evaluation function is made into a new evaluation function. Thereafter, the step is repeatedly obtained as long as the value of the step is equal to or larger than a threshold determined according to the value of the first step, and the position where the step is placed is made into the one for the make/break of the dial pulse. Thus, a dial pulse signal under the telephone call can be surely detected.

Description

[Detailed description of the invention] Anti-dokoku! The present invention relates to a dial pulse detection method, and more particularly to a dial pulse detection method for detecting a dial pulse dialed during a call from a call signal.

Originally, dial pulses (DP) were used to transmit dial information between telephones and exchanges, and were not used during calls. However, dial pulses were used to transmit various information. There is an increasing demand for the dial pulse signal to be used even during a call as a means of communication.However, since the dial pulse signal has repeated make and break cycles and is a step-like change in high voltage, the waveform as it is cannot be passed through the call path. However, it is difficult to detect this reliably.

SUMMARY OF THE INVENTION An object of the present invention is to provide a dial pulse detection method that can reliably detect dial pulse signals during a call.

According to the present invention, there is provided a dial pulse detection method for detecting dial information transmitted from a telephone via a subscriber cable, an exchange, and various transmission devices, the method comprising: means for analyzing the output signal of the synthesis filter by regarding the transmission device as a synthesis filter, and obtaining a step response of the synthesis filter; and obtaining a cross-correlation between the output signal and the step response and outputting this as an evaluation function. means for determining the autocorrelation of the step response, placing a first step at the position of the maximum absolute value of the evaluation function, and calculating the autocorrelation of the step from the evaluation function at the position where the step is placed. A new evaluation function is obtained by normalizing the size and subtracting it, and from this evaluation function, a means for similarly calculating a step during which the step size is equal to or greater than a value determined according to the size of the first step is provided. A dial pulse detection method is obtained, which is characterized in that the position where this step is placed is the make or break position of the dial pulse.

Superintendent K The present invention will be described in detail below using the drawings.

FIG. 1 is a system block diagram of an embodiment of the present invention.
In the figure, the output information from Telephone IT includes subscriber couple 21. Exchange a221 Transmission line 23 including various transmission devices
．． The signal is introduced into the dial pulse detection device 3 via the exchange 24. This dial pulse detection device 3 includes a subscriber cable 21, an exchange 22 . Transmission line 23. exchange fi
24 is regarded as a synthesis filter, and dial pulse information is detected from the output signal X of this synthesis filter.

The dial pulse detection device 3 includes an input signal analysis section 31 that analyzes the input signal X to obtain a coefficient A of the synthesis filter 2;
Step response R of the synthesis filter 2 having this A as a coefficient
a step response section 32 that obtains the cross-correlation φX between the input signal X and the step response R and uses this as the initial value of the evaluation function; It has a correlation section 34 and a method search section 35 that performs a step search using an evaluation function and an autocorrelation.

Here, the dial pulse output of the telephone IT is a rectangular make and break signal, but the signal is band-limited midway and is input to the dial pulse detection device 3. telephone 1
If the communication path between the dial pulse detector 3 and the dial pulse detector 3 is considered as a synthesis filter 2, the input to the dial pulse detector 3 can be considered as a response when a step is input to the synthesis filter. Therefore, if the step response of the synthesis filter 2 is known, the make and break positions can be specified.The transfer function of the 0 synthesis filter can be found by analyzing the input signal X of the dial pulse detection device 3. As an example of the 0 analysis method, a linear predictive analysis method can be used. Once the transfer function of the synthesis filter is determined, its step response can be easily calculated using the speech encoding technology proposed in the past. It is possible to ask for it.

Based on the above, the input signal X is analyzed by the analysis section 31, and the coefficient A of the synthesis filter 2 is determined.

Step response R of the synthesis filter 2 having this A as a coefficient
is determined by the step response unit 32, and the cross-correlation φxr between the input signal X and this step response R is determined by the cross-correlation unit 33. Further, the autocorrelation φrr of the step response R is determined by the autocorrelation unit 34.

The cross-correlation φ×r obtained by the cross-correlation unit 33 is used as the initial value of the evaluation function E, and a step search is performed in the step search unit 35 using this evaluation function E and the autocorrelation φr. The figure shows the operation flow of the step search method in the step search section 35.

In step search, the number of evaluations E(i) of length I×, i=
1~■ Find the maximum value IE(in)l of the absolute value of Subtract the autocorrelation φ" of Ir with the magnitude Δ at the position in, i.e. ~ E (in) = E (i) − Δ×φrr(li−1n
l) (1=1 to IX). In the same way, repeat the step while the step size is greater than the threshold determined according to the first step size, and set the position of the step to the make and break position of the dial pulse! That is to say.

In Fig. 2, in is the make or break position of the dial pulse, g (in) is the step size at position in, Δ is the step size, and T is the first step size g (il). The threshold value of the step size is determined accordingly, and α is a coefficient for determining the threshold value.

Effects of the Invention As described above, according to the present invention, the make or break position of the dial pulse can be determined as a position where the correlation between the step response and the input signal is large, so that the dial pulse during a call can be accurately determined. This has the effect that it is possible to perform the detection.

[Brief explanation of the drawing]

Fig. 1 is a system program diagram of an embodiment of the present invention;
This figure is an operation flow diagram of the step search section of FIG. 1. Explanation of symbols of main parts 1... Telephone 2... Synthesis filter 3... Dial pulse detection device 31...
- Input signal analysis unit 32... Step response unit 33... Cross correlation unit 34... Auto correlation unit 35... Step search unit

Claims (1)

[Claims] (1) A dial pulse detection method that detects dial information sent from a telephone via a subscriber cable, an exchange, and various transmission devices, the subscriber cable,
Means for analyzing the output signal of the synthesis filter by regarding the exchange and various transmission devices as a synthesis filter and obtaining a step response of the synthesis filter; means for outputting the autocorrelation of the step response; a means for determining the autocorrelation of the step response; a first step is placed at the position of the maximum absolute value of the evaluation function; and the autocorrelation is calculated from the evaluation function at the position where the step is placed. is normalized to the step size and subtracted as a new evaluation function, and from this evaluation function, similarly calculate the step while the step size is greater than or equal to the value determined according to the first step size. provide means,
A dial pulse detection method characterized in that the position where this step is placed is the make or break position of the dial pulse.