JPS5820513B2 - Tashiyuuhashingoujiyushinki - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a multi-frequency signal receiver in an in-band multi-frequency signal system that transmits dial information and the like in the form of a multi-frequency signal using a voice band.

The basic operating principle of the multi-frequency signal receiver of the present invention is to separate the received multi-frequency signal into multi-frequency groups, compare the sine wave of each group with a certain threshold value, convert it into a rectangular wave, and then convert the multi-frequency signal into a rectangular wave. It measures frequency.

For example, one of the simplest methods is to generate clock pulses separately and count the number of clock pulses that enter one cycle of the rectangular wave to measure the frequency of the sine wave.

Conventionally, in this type of receiver, the threshold value is fixed, but the feature of the present invention is that the threshold value is not fixed;
The purpose is to strengthen the malfunction prevention function of the multi-frequency signal receiver by changing it according to the input signal level.

For this reason, the multi-frequency signal receiver of the present invention includes means for measuring the average level of the input signal (or a band component of a portion thereof), and generating a voltage proportional to the measured value and providing this as the threshold value. and means.

Each of these means can be realized by an analog circuit or a digital circuit.

In voice in-band signaling, regular multi-frequency signals are transmitted using the same band as voice.

Therefore, the receiver must be careful not to misidentify a pseudo signal such as a voice as a multifrequency signal.

One of the differences between a multifrequency signal and a pseudo signal is that the former has almost no amplitude fluctuations, whereas the latter has considerably large fluctuations.

However, when using a fixed threshold value in a multi-frequency signal receiver of the type mentioned above, the threshold value must be set quite low in order to be able to receive the multi-frequency signal with the minimum amplitude defined by the standard.

Therefore, even if there is some amplitude variation in the input signal, the rectangular wave output from the threshold circuit will hardly change, and the difference between the multifrequency signal and the pseudo signal cannot be detected, so it will be received as a regular multifrequency signal. There was a risk.

On the other hand, if you change the threshold according to the signal level and set the threshold close to the signal peak value, if there is an amplitude fluctuation and the peak value falls, the signal amplitude will not exceed the threshold and the rectangular wave will be generated. Since the period of is no longer constant, it is not determined to be a regular multi-frequency signal, and no malfunction will occur.

- 10,000, since there is almost no amplitude fluctuation in a regular multi-frequency signal, there is no problem because the signal peak value does not exceed or do not exceed the threshold value, and it operates normally.

That is, the present invention attempts to detect amplitude fluctuations, which are differences in waveforms between a pseudo signal and a regular multifrequency signal, by making the threshold variable.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings, mainly regarding a clock pulse counting type multi-frequency signal receiver.

FIG. 1 is a block diagram schematically showing a clock pulse counting type multifrequency signal receiver.

A multi-frequency signal applied to the input terminal 1 is separated into a low group signal 4 and a high group signal 5 by a low-frequency P-wave device 2 and a high-frequency P-wave device 3, respectively.

These signals are compared with thresholds 6 and 7 by a threshold circuit 8.9 and converted into a rectangular wave 10.11, which is input to a low group frequency measurement circuit 12 and a high group frequency measurement circuit 13.

In each frequency measurement circuit, a separate clock pulse generator 14 is provided.
The frequency is measured by counting and processing the clock pulses 15 generated by the square wave according to the timing of the rectangular wave.

The measurement results 16 and 17 of each group are finally judged as multi-frequency signals by the comprehensive judgment circuit 18, and the results are outputted to the output terminal 19.

FIG. 2 is a diagram showing waveforms of various parts of FIG. 1 when a pseudo signal is input, especially on the low group side.

If the low-frequency F wave device output signal 4 is an irregular signal, there is no need to worry about malfunction, but if it crosses the threshold 6 fairly regularly even if there is some amplitude fluctuation as shown in FIG. The output 10 of the threshold circuit 8 is no different from a rectangular wave when a regular multi-frequency signal is input.

Since the low group frequency measurement circuit 12 in FIG. 1 measures the frequency of the signal 4 from the rectangular wave 10 and the clock pulse 15, it will recognize it as a correct multifrequency signal in the case shown in FIG. 2. become.

If this happens at the same time even in a high frequency group, a malfunction will occur and the signal will be regarded as a regular multi-frequency signal even though it is a pseudo signal.

As a measure to prevent such malfunctions, it is considered effective to set the threshold value 6 high so that it does not cross the threshold value when amplitude fluctuation occurs and the peak value of the waveform decreases.

However, since it is necessary to receive a signal with the minimum amplitude specified by the multi-frequency signal reception standard, if a fixed threshold value were to be provided, it would have to be set low, and such measures to prevent malfunctions could not be taken.

FIG. 3 is a waveform diagram showing the principle of the present invention.

In the present invention, the threshold value 6 is made variable and is set according to the input signal amplitude level, so the threshold value 6 can be set near the peak value of the signal regardless of the magnitude of the input signal.

Even if the signal 4 is the same as the signal shown in FIG. 2, the rectangular wave 10 output from the threshold circuit 8 has an irregular waveform because the threshold value 6 is set high as shown in FIG.

Therefore, normal operation of the frequency measuring circuit is prevented and no malfunction occurs.

On the other hand, when a regular multi-frequency signal is input, the signal 4 has a waveform with almost no amplitude fluctuation, so the rectangular wave 10 has a regular waveform and operates normally, so there is no problem.

FIG. 4 is a block diagram showing an embodiment of the present invention in which only the threshold value on the high group side is made variable.

Blocks that perform the same functions as in FIG. 1 are numbered the same.

First, the input signal applied to the input terminal 1 is passed through the high-pass filter 3 to extract only the high group signal 5.

The high group signal 5 is converted into a rectangular wave by the threshold circuit 9, and the threshold 46 used at that time is not fixed but is set according to the average level of the signal 5.

That is, the signal 5 passes through a rectifier circuit 41 and a smoothing circuit 42, and its average level 47 is detected, and then a threshold value 46 close to the peak value of the high group signal 5 is detected through an amplifier 48 having an appropriate gain. generated.

At this time, it is necessary to make sure that a certain threshold value 46 appears even when inputting, so the output signal 48 of the amplifier 43 and the constant value 45 are added together by the adder circuit 44 to obtain the threshold value 46. .

It is also possible to use a square circuit in place of the rectifier circuit 41 in the circuit of FIG.

In addition, in order to enhance the malfunction prevention function, the smoothing circuit 42
It is desirable to use a type of circuit in which the output rises quickly when an input is received, and the output decays slowly when the input is removed.

This is because it is better to set the threshold near the peak value as soon as possible when an input signal is input, and to keep the threshold constant even if the peak value decreases due to amplitude fluctuations as shown in Figure 3. This is because it is effective in detecting fluctuations.

When such a smoothing circuit with rise and fall characteristics is constructed using an analog circuit, it can be easily created by combining transistors, resistors, and capacitors.

Further, it is also possible to perform a similar operation using a digital circuit.

In the embodiment shown in FIG. 4, a fixed threshold value 6 is used on the low group side, but it is of course effective to make this variable as well.

Further, in this embodiment, the input to the rectifier circuit 41 is the high group signal 5, but the signal applied to the input terminal 1 can also be used as is.

Although this text mainly describes an example applied to a clock pulse counting type multi-frequency signal receiver, the present invention is generally applicable to a type of multi-frequency signal receiver that converts a multi-frequency signal into a rectangular wave and then measures the frequency. Applicable to all vessels.

For example, the method of multi-frequency signal receivers currently in practical use converts each group of multi-frequency signals into a rectangular wave, and then determines the frequency appropriate for a group of resonant circuits tuned to each multi-frequency signal frequency. However, it can also be applied to such a method.

As explained above, the multi-frequency signal receiver of the present invention has its own malfunction prevention function and is extremely effective in protecting against pseudo signals.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an example of a multi-frequency signal receiver before the improvements of the present invention are made. 8.9 is a threshold value, 8.9 is a threshold circuit, 12 and 13 are frequency measurement circuits, 14 is a clock pulse generator, 18 is a general judgment circuit, and 19 is an output terminal. FIG. 2 is a diagram showing waveforms of various parts of the circuit of FIG. 1, and shows an example of a case where a false signal causes a malfunction. FIG. 3 is a waveform diagram showing the principle by which malfunctions can be prevented in the multi-frequency signal receiver of the present invention. FIG. 4 is a diagram showing an embodiment of the present invention, in which 41 is a rectifier circuit, 42 is a smoothing circuit, 43 is an amplification circuit, 44 is an adder circuit,
46 is a variable threshold value.

Claims (1)

[Claims] 1. In a multi-frequency signal receiver that measures the frequency of each group of a hindlimb multi-frequency signal obtained by separating frequency groups of the multi-frequency signal and comparing the sine waves of each group with a threshold value and converting them into rectangular waves,
A multi-frequency signal comprising means for detecting an average level of at least some band components of an input signal, and means for generating a voltage proportional to the average level and applying it as the threshold. receiver.