JPH04307839A - Communication equipment - Google Patents

Abstract

PURPOSE:To realize the communication equipment provided with a call signal detection means able to flexible cope with the standard of a different call signal from each country. CONSTITUTION:The output of a 1st charge/discharge circuit 6 charged/ discharged by the output of a photocoupler 5 connected to lines 1, 2 is compared with a reference voltage resulting from the output of a charge/discharge circuit 8 charged and discharged by the output of the circuit 6 at a comparator. Thus, the reference voltage for call signal detection is subjected to variable control in response to a signal level so as to allow the equipment to cope with a call signal of a different standard.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a communication device, and more particularly to a communication device having means for detecting a calling signal from a line.

0002

2. Description of the Related Art Conventionally, communication devices have been known in telephone networks and the like that detect a call signal transmitted from an exchange and automatically answer the call signal.

Conventionally, in this type of communication device, a constant voltage diode is used to turn on a photocoupler only when a signal exceeds a certain voltage, and the voltage obtained by smoothing the output of the photocoupler is converted to a fixed voltage by a final stage comparator. A calling signal detection circuit was used to compare with.

0004

[Problems to be Solved by the Invention] On the other hand, the standards for calling signals are not common internationally, and the levels and frequencies differ from country to country.

However, in the above-mentioned conventional example, since the final stage comparator compares the voltage with a fixed voltage, considering, for example, that it corresponds to the call signals of European countries,
It detects call signals with different levels and frequencies depending on the country, and also prevents malfunctions due to noise.
It was difficult to meet the standards and standards of each country.

[0006] For this reason, in conventional configurations, countermeasures were taken such as switching the breakdown voltage of the constant voltage diode to different settings depending on the country and changing the time constant of the smoothing part. In some cases, the level and frequency of the signal was wide, and it was not possible to handle it simply by adjusting the voltage regulator diode and time constant.

[0007] Therefore, in the past, it was necessary to change parts such as constant voltage diodes according to the specifications of the calling signal before shipping, or to set values corresponding to the country by changing switches, etc. There was a problem that manufacturing costs increased.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and provide a communication device having a call signal detection means that can flexibly adapt to different call signal standards depending on the country.

[0009]

[Means for Solving the Problems] In order to solve the above-mentioned problems, the present invention provides a communication device having means for detecting a calling signal from a line. a first charging/discharging circuit that is charged and discharged by the output of the detection means; a second charging and discharging circuit that is charged and discharged by the output voltage of the first charging and discharging circuit;
The output voltage of the first charging/discharging circuit is set as a reference voltage value, the output voltage of the first charging/discharging circuit is compared with the reference voltage value, and the comparison circuit is configured to output a comparison output as a call signal detection signal. .

0010

[Operation] According to the above configuration, the output of the first charging/discharging circuit, which is charged/discharged by the detection output corresponding to the AC signal on the line, is connected to the second charging/discharging circuit, which is charged/discharged by the output voltage of the first charging/discharging circuit. A calling signal detection signal is generated by comparing the output voltage of the charging/discharging circuit.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be explained in detail below based on embodiments shown in the drawings.

FIG. 1 shows the configuration of a paging signal detection circuit for a communication device according to the present invention.

In FIG. 1, numerals 1 and 2 are input terminals connected to a telephone line, and 3 is an output terminal of a detection circuit, which becomes low level when a calling signal is detected.

Reference numeral 4 is a constant voltage diode inserted in series on the line, and 5 is a photocoupler. In order to detect the calling signal which is an alternating current signal, two of them with opposite polarities are connected in parallel to the line as shown in the figure. is connected to.

Reference numeral 6 denotes a charging/discharging circuit that charges and discharges by the output of the photocoupler 5. The charging/discharging circuit 6 includes a diode 23, resistors 21, 22, and a capacitor 24, and the resistor 21 is larger than the resistor 22 (approximately 10 times larger).

The output of the charging/discharging circuit 6 is connected to a comparator 11.
becomes the input.

Reference numeral 7 denotes a buffer amplifier (voltage follower with sufficiently high input impedance) that receives the voltage of the charging/discharging circuit 6.

Reference numeral 8 denotes a charging/discharging circuit that charges/discharges by the output of the buffer 7, which includes resistors 25, 26, a diode 27,
It consists of a capacitor 28. The resistor 26 is slightly larger (about several times) larger than the resistor 22, and the resistor 25 is larger (about 10 to several tens of times) larger than the resistor 26.

Reference numeral 9 is an amplifier, 10 is a Zener diode that limits the output voltage of the amplifier 9, and the power supply voltage (+
5V).

The output of the charge/discharge circuit 8 passes through an amplifier 9 and a Zener diode 10 and becomes a reference input to a comparator 11.

In the above configuration, when a calling signal is input between 1 and 2 from the line, one of the photocouplers 5 is turned on only when the input signal exceeds the breakdown voltage of the constant voltage diode 4.

When one of the photocouplers 5 is turned on, the transistor 12 is turned on, and the charge stored in the capacitor 4 of the charging/discharging circuit 6 is discharged through the diode 23 and the resistor 22. Although it is discharged through the resistor 21, in the charging/discharging circuit 6, as mentioned above, the resistor 21 is
It is made larger (about 10 times) than the resistor 22, and the discharge time constant is almost determined by the resistor 22 and the capacitor 24. Therefore, in the charging/discharging circuit 6, the charging time constant is larger than the discharging time constant.

When the voltage of the capacitor 24 of the charging/discharging circuit 6 decreases due to the above-mentioned discharge, the voltage is transmitted to the charging/discharging circuit 8 by the buffer 7 . Then, the charge stored in the capacitor 28 is transferred to the resistor 2 by the amount that the voltage of the buffer 7 has decreased.
6. Discharge through diode 27. Also in the charging/discharging circuit 8, the resistor 25 is larger (10 times to more) than the resistor 26.
(about several tens of times), the discharge time constant is determined by the resistor 26 and capacitor 28.

Next, when both photocouplers 5 are turned off, the transistor 12 is turned off and the capacitor 24 is discharged via the resistor 21. The time constant at this time is resistance 2
1 and the capacitor 24, but as mentioned earlier, this charging time constant is larger than the discharging time constant.

When the voltage of the capacitor 24 increases due to this charging, it is transmitted to the charge/discharge circuit 8 by the buffer 7, and the capacitor 28 is charged via the resistor 25. The charging time constant at this time is determined by the resistor 25 and capacitor 28, and is also made larger than the charging time constant.

The voltage of the charging/discharging circuit 8 is amplified a little by the amplifier 9 (approximately 1.5 to 2 times) and becomes a reference voltage for the comparator 11 . The Zener diode 10 prevents this reference voltage from exceeding a certain voltage (4 to 4.5 V), which is slightly smaller than the power supply voltage (+5 V).

The input signal of the comparator 11 is the voltage of the charging/discharging circuit 6, and it compares this with the reference voltage mentioned above and outputs the signal 3.

FIGS. 2 and 3 show waveforms at various parts. FIG. 2 shows a case where the signal level is low, the on time of the photocoupler is short, and the off time is long.

In FIGS. 2 and 3, reference numeral 31 is a calling signal, 32 is the output of the photocoupler 5, and 33 is the voltage of the capacitor 24, which is also an input signal to the comparator 11. 34 is the reference voltage of 11 comparators, 3
5 is the output signal 3 of the comparator 11.

FIG. 3 shows that the signal level is high or the breakdown voltage of the voltage regulator diode 4 is high (depending on the product specifications).
(These are relative conditions), the on-time of the photocoupler 4 is long and the off-time is short.

In FIG. 3, reference numeral 41 indicates a calling signal;
24 is the output of the photocoupler 5, and 43 is the voltage of the capacitor 24, which is also the input signal of the comparator 11. 44 is the reference voltage of the 11 comparators, and 45 is the output signal 13 of the comparator 11.

As is clear from the comparison between FIGS. 2 and 3, even if the voltage of the input call signal is different from the breakdown voltage of the constant voltage diode 4, in this embodiment, Since the reference voltage of the comparator 11 is the quadratic integral value obtained by the charge/discharge circuit 6 and the charge/discharge circuit 8, by making the reference voltage of the comparator 11 variable according to the input signal waveform of the comparator 11, the comparator 11 When the level of the signal waveform is low, it is compared with a low reference voltage, and when the level is high, it is compared with a high reference voltage, and it can be seen that output signal 3 with almost equal on/off time ratio can be obtained. .

Therefore, the ability to detect a calling signal can be improved, and even if the standards for calling signals differ from country to country, such as in European countries, similar calling signal detection results can be obtained using the same circuit (constant). It is possible,
Pre-shipment adjustment work can be omitted and manufacturing costs can be reduced.

Furthermore, the configuration of this embodiment is more resistant to disturbances such as noise than the conventional configuration.

The conventional configuration corresponds to one in which the buffer amplifier 7, charging/discharging circuit 8, amplifier 9, and Zener diode 10 in FIG. However, Figure 2
, 3, and 41 in FIG. 3, the reference voltage supplied to the comparator 11 must be at a high level.

However, when the reference is made high, the photocoupler is accidentally turned on due to noise or the like, and the charge in the capacitor 24 is discharged, and when the output signal 3 becomes low level, it does not return to high level easily, and the noise is used as a calling signal. Although there is a risk of erroneous detection, this embodiment does not have such a problem.

FIG. 4 shows this situation. In FIG. 4, 51 is a calling signal, 52 is the output of the photocoupler, and 53 is 24
, 54 is the reference voltage of the comparator in this embodiment, 55 is the reference voltage of the conventional fixed voltage, and 56 is the output signal 3 of the comparator 11.

As can be seen from the comparison of the waveforms of the solid line and broken line 56, in the conventional example, the low level time is quite long, which causes false detection on the communication device side using this circuit, but in the present example In this case, the output signal is at a low level only during approximately the pulse width, and only the calling signal can be accurately detected without causing false detection.

The above-mentioned call signal detection circuit can be applied to various communication devices such as telephones, facsimile machines, and various data terminals.

[0040]

As is clear from the above, according to the present invention, in a communication device having means for detecting a calling signal from a line, means for detecting an AC signal on the line;
A first charge/discharge circuit that charges and discharges based on the output of the detection means, a second charge/discharge circuit that charges and discharges based on the output voltage of the first charge/discharge circuit, and an output voltage of the second charge/discharge circuit. is taken as a reference voltage value, and the configuration includes a comparison circuit that compares this reference voltage value with the output voltage of the first charge/discharge circuit and outputs the comparison output as a call signal detection signal. The output of a first charging/discharging circuit that charges/discharges based on a detection output corresponding to an AC signal is converted into the output voltage of a second charging/discharging circuit that charges/discharges based on an output voltage from the first charging/discharging circuit, that is, an input signal. By comparing with a correspondingly variable reference voltage, it is possible to always generate an equivalent ringing signal detection signal even if there are relative differences in the level of the input ringing signal, thus making it possible to adjust or change settings for different ringing signal standards. Therefore, it is possible to provide an excellent communication device that can easily and inexpensively detect a calling signal without the need for , and has a calling signal detecting means that is resistant to disturbances such as noise.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a paging signal detection circuit of a communication device according to the present invention.

FIG. 2 is a waveform diagram of each part of the circuit when a call signal is input to the circuit of FIG. 1;

FIG. 3 is a waveform diagram of each part of the circuit when a call signal is input to the circuit of FIG. 1;

4 is a waveform diagram of various parts of the circuit when pulse noise is input to the circuit of FIG. 1; FIG.

[Explanation of symbols]

1, 2 Telephone line 3 Detection signal 4 Constant voltage diode 5 Photo coupler 6, 8 Charge/discharge circuit 7 Buffer amplifier 9 Amplifier 10 Zener diode 11 Comparator 12 Transistor 21, 22, 25, 26 Resistor 23, 27 Diode 24, 28 Capacitor 31 , 41 Call signal 32, 42, 52 Photocoupler output waveform 33, 43
, 53 Voltage of capacitor 24 34, 44, 54
Reference voltage 55 of comparator 11 Threshold voltages 35, 45, 56 3 detection signals

Claims (1)

[Claims] Claims: 1. A communication device having means for detecting a calling signal from a line, including means for detecting an alternating current signal on the line;
a second charging/discharging circuit that charges and discharges using the output voltage of the first charging/discharging circuit, and an output voltage of the second charging/discharging circuit as a reference voltage value, and this reference voltage value and A communication device comprising a comparison circuit that compares output voltages of the first charge/discharge circuit and outputs a comparison output as a call signal detection signal.