JPH01198894A - Dial pulse detecting system - Google Patents

Abstract

PURPOSE:To accurately detect a dial pulse under a telephone call by obtaining a position, at which the correlation between a step response and an input signal is large, as the one for the make/break of the dial pulse. CONSTITUTION:A cross-correlation phixr between an input signal X and a step response R of a synthesizing filter 2 is obtained at a cross-correlation part 31, and step searching is executed at a step searching part 32 by using the cross-correlation phixr. Namely, a first step is placed at the position where the absolute value of the cross-correlation is the maximum, and after that, the step is successively obtained at the position where the absolute value of the cross-correlation is the maximum except previously determined ranges before and after the position where the step is placed as long as the value of the step is equal to or larger than a value determined according to the value of the first step. Thereafter, 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

TECHNICAL FIELD 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 a growing demand for the use of mobile phones even during calls 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 does not pass through the communication path, making it difficult to detect it reliably.

An object of the present invention is to provide a dial pulse detection method that can reliably detect a dial pulse signal during a call.

1. According to the present invention, there is provided a dial pulse detection method for detecting dial pulse information transmitted from a telephone set via a subscriber cable, a switchboard, and various transmission devices, and the dial pulse detection method detects dial pulse information transmitted from a telephone set via a subscriber cable, a switchboard, and various transmission devices. a means for determining the cross-correlation with a response; a first step is placed at a position where the absolute value of the cross-correlation is maximum, and thereafter the absolute value of the cross-correlation is the maximum except for a predetermined range before and after the position where the step is placed; means for sequentially determining steps while the step size is greater than or equal to a value determined according to the first step size, and the step position is set as the make or break position of the dial pulse. A dial pulse detection method is obtained which is characterized by the following.

1st Sat. Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a system block diagram of an embodiment of the present invention.
In the figure, output information from telephone 1 is transmitted from subscriber cable 21. Exchange 1122. Transmission path 2 including various transmission devices
3. The signal is introduced into the dial pulse detection device 3 via the exchange 24. In this dial pulse detection device 3,
Subscriber cable 21, exchange 22. Transmission line 23. Exchange 8
124 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 detects the cross-correlation φx between the input signal X and a predetermined step response R of the synthesis filter 2.
It has a cross-correlation section 31 that calculates r, and a step search section 32 that performs a step search using this cross-correlation.

Here, the dial pulse output of the telephone set 1 is a rectangular make and break signal, but it is input to the dial pulse detection device 3 after being subject to a band limit. '@ If the communication path between R1 and the dial pulse detection device 3 is considered as the synthesis filter 2, the input to the dial pulse detection device 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, it is possible to specify the make and break positions.The synthesis filter 2 can be thought of as a bandpass filter that has the same transmission characteristics as an average communication path. , Therefore, since the step response R of this synthesis filter 2 is known in advance, it is assumed that this R is determined in advance.

Then, the cross-correlation φ× between the input signal X and the step response R
The cross-correlation section 31 calculates ", and the step search section 32 performs a step search using this cross-correlation φ x " to detect a position where the correlation between a predetermined step response R and the input signal X is large. This detection position becomes the dial pulse make and break position.

FIG. 2 is a flowchart showing a step search method in the step search section 32, which uses a conventionally proposed speech encoding technique.

In this step search, the cross-correlation φxr(t
), maximum absolute value of i=1 to IX 1φ×r(in )
Find I and place a step of size Δ=φ×(tn) at position 1n.

In the second and subsequent steps, the steps are repeatedly determined while the size of the step is greater than or equal to the threshold value determined according to the size of the first step, except for a predetermined range before and after the position where the step has already been placed, and the step is placed. This position is the make or break position of the dial pulse.

In Fig. 2, in is dial pulse make,
The break position, g (in) is the step size at position 1n, Δ is the step size, T is the step size threshold determined according to the first step size g(il), and α is the threshold value. This is the coefficient to calculate.

According to the present invention, the positions where the correlation between the step response and the input signal is large can be determined as the make and break positions of dial pulses, so dial pulses 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 block diagram of an embodiment of the present invention, and FIG. 2 is a flowchart showing the operation of the step search section of FIG. Explanation of symbols of main parts 1...Telephone 2...Synthesis filter 31...Cross correlation section 32...Step search section

Claims (1)

[Claims] (1) A dial pulse detection method that detects dial pulse information sent from a telephone via subscriber cables, exchanges, and various transmission devices, and means for determining the cross-correlation between an input signal and a predetermined step response. Then, the first step is placed at the position where the absolute value of the cross-correlation is maximum, and the size of the step is placed at the position where the absolute value of the cross-correlation is maximum, except for a predetermined range before and after the position where the step is placed. and means for sequentially determining steps for a period of time equal to or greater than a predetermined value depending on the magnitude of the first step, and the position where the step is placed is set as the make or break position of the dial pulse. Detection method.