JPS5834997B2 - 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 each frequency group, 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, as the simplest method, the frequency of the sine wave can be measured by separately generating clock pulses and counting the number of clock pulses that enter one cycle of the rectangular wave.

Conventionally, in this type of receiver, the above-mentioned threshold value was single, but the feature of the present invention is that a plurality of threshold values, each different from each other, are provided, and the threshold value crossed by the sine wave is set as much as possible. By selecting , the threshold value is substantially moved according to the input signal level, and the purpose is to strengthen the malfunction prevention function of the multi-frequency signal receiver.

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, if a single threshold value is used 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 of the minimum amplitude defined by the standard.

For this reason, even if there is some amplitude variation in the input signal, the rectangular wave output from the threshold circuit hardly changes, and there is a risk that it will be received as a regular multi-frequency signal.

In order to eliminate this drawback, the multi-frequency signal receiver of the present invention:
A plurality of different threshold values are prepared, and the most dog-like one is selected depending on the input signal level.

In this way, if the signal amplitude fluctuates and the peak value decreases, the lower threshold will be crossed, but the relatively high threshold that has been selected will not be crossed.

Therefore, the period of the obtained rectangular wave will not be constant, and it will not be determined to be a regular multi-frequency signal, and no malfunction will occur.

On the other hand, when a regular multi-frequency signal is input, there is almost no amplitude variation, and the peak value of the signal always exceeds the selected threshold value, so the system operates without problems.

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 threshold circuits 8 and 9, respectively, and converted into rectangular waves 10 and 11, which are input to a low group frequency measuring circuit 12 and a high group frequency measuring circuit 13.

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

The measurement results 16 and 1[gamma] 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.

When the output signal 4 of the low-frequency p-wave device is an irregular signal, there is no need to worry about malfunction, but 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 in the high group, it will cause a malfunction, and even though it is a pseudo signal, it will be regarded as a regular multi-frequency signal.As a measure to prevent such malfunction, set the threshold value 6 high, It is considered effective to prevent the threshold value from being crossed when the peak value of the waveform decreases due to amplitude fluctuation.

However, since it is necessary to receive a signal with the minimum amplitude determined by the multi-frequency signal reception standard, it cannot be set high when a single threshold value is provided.

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

FIG. 3 shows vl, v2. The case where three threshold values of v3 are provided is shown.

If only the lowest threshold value v1 is used, the resulting rectangular wave is a in FIG. 3, and there is a risk of malfunction as described above.

On the other hand, if a threshold value v2 higher than vl is used, when there is an amplitude fluctuation, the waveform becomes an irregular rectangular wave as shown in FIG. 3, and is not determined to be a regular multifrequency signal, so that no malfunction occurs.

Since the highest threshold ■3 is not reached, the threshold is v2.
All you have to do is select.

FIG. 4 is a block diagram showing an embodiment of the present invention,
The same components as in FIG. 1 are given the same numbers.

In this embodiment, only the low group side has multiple threshold values, and the high group side has a single threshold value, but it goes without saying that multiple threshold values and deviations for both groups are more effective.

In FIG. 4, the low group signal \j4 is the threshold value circuit 52゜54.
56 for a plurality of thresholds i′L! ! ,51,53.55(
For example, it is compared with V 1 + V 2 t V-3 in FIG. It is input to the selection circuit 60.

Among these rectangular waves, the rectangular wave (b in the example of FIG. 3) obtained by comparing with the highest possible threshold is selected by the selection circuit 60 and sent to the frequency measurement circuit 12 as an output signal 61.

The frequency measuring circuit 12 counts the cock pulses 15 to measure the frequency of the input rectangular wave 61 (that is, the frequency of the low group signal 4), and outputs a measurement result 16.

The comprehensive determination circuit 18 finally determines the input multi-frequency signal from the low group frequency measurement result 16 and the high group frequency measurement result 11, and outputs the result as a signal 19.

Once selected, the rectangular wave is used continuously while frequency measurement is being performed, but if it is determined that the input signal is not a regular multifrequency signal as a result of frequency measurement or comprehensive judgment, it is immediately reset and input A new selection is made in response to the signal.

Further, if the signal exceeds a threshold higher than the previously selected threshold, a rectangular wave obtained by comparison with the higher threshold is newly selected.

When the selected rectangular wave changes in this way, a new frequency measurement is performed from that point onwards.

FIG. 5 is a diagram showing a specific example of the threshold circuit and selection circuit 60 for multiple threshold values.

Thresholds 51, 53, and 55 are low, medium, and high thresholds (eg, vl, v2, v3 in FIG. 3), respectively.

A signal 59 obtained by comparing the low group signal 4 with the high threshold 55 is provided as a set input to a flip-flop 67.

Now consider the case where signal 4 has a peak value higher than high threshold value 55.

At this time, once the signal becomes 1''', the flip-flop 61
is set and the output signal 68 of the flip-flop is 1"
'.

Thereby, the square wave 58 obtained by comparison with the intermediate value 53 is inhibited by the gate 69.

The fact that the flip-flop 6γ is set means that the flip-flop 63 is always set (if that is the case, the threshold value 53 is lower than the threshold value 55), so the low threshold value 51
The square wave 57 obtained by comparing with the high threshold value 55 is also inhibited by the gate 1-65, and what ultimately passes through the OR gate 71 and becomes the signal 61 is the square wave 59 obtained by comparing with the high threshold value 55.

Considering the same way, if the peak value of the signal 4 is between the high threshold value 55 and the intermediate image 53, the rectangular wave 58 and the signal 4
When the peak value of is between the intermediate image 53 and the low threshold value 51, the rectangular wave 57 is inputted to the frequency measurement circuit as a signal 61, respectively.

In this case, the minimum threshold value 51 must be set so that a multifrequency signal with the minimum amplitude defined by the multifrequency signal reception standard can be received.

Furthermore, once the flip-flops 63 and 67 are set, as a result of frequency measurement or comprehensive judgment, if it is judged that the input signal is not a regular multi-frequency signal, they are immediately reset based on the judgment result 62, and the threshold value is newly selected. will be redone.

The greater the number of threshold values, the more consistent the malfunction prevention function can be expected over a wider level range of input signals.

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

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 passes it through a group of resonant circuits tuned to the frequency of each multi-frequency signal to determine the 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 to which the present invention is applied.
12.13 is a frequency measurement circuit, 14 is a clock pulse generator, 18 is a comprehensive judgment circuit, 19 is an output terminal. be. 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 block diagram showing one embodiment of the present invention.
, 53.55 are the low, instep, and high thresholds, respectively, and 52, 54,
56 is a threshold circuit, and 60 is a selection circuit. FIG. 5 is a circuit diagram showing an embodiment of the threshold circuit and selection circuit of FIG. 4, in which 63.67 is a flip-flop;
is a reset signal.

Claims (1)

[Claims] 1 means for separating frequency groups of a multi-frequency signal to obtain sine waves for each group; a plurality of comparison circuits for comparing the sine wave amplitudes with different threshold values; means for selecting the output rectangular wave of the threshold comparison circuit; means for measuring the frequency of each group of the multi-frequency signal using the selected rectangular wave; A multi-frequency signal receiver comprising: a comprehensive determination circuit that determines whether a multi-frequency signal has been received.