JPH0732423B2 - Call response detection method - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a call response detection system for a telephone exchange.

[Background of the Invention]

Conventionally, a ringing signal sending method has been proposed in which one line on the battery side of a calling current supply circuit is used for sending a ringing signal, but a circuit dedicated to detecting a ringing response is required for ringing response detection. This will be described with reference to the drawings. FIG. 2 is a diagram showing an example of a conventional call signal transmission and response detection circuit. In FIG. 2, 101 is a subscriber terminal, 102 is a subscriber line, and 103 and 104.
Is a switch for supplying current with A-line battery and B-line ground (hereinafter abbreviated as normal), 105 and 106 are switches for supplying current with A-line ground and B-line battery (abbreviated as Levers), 107 and 108 Is a call signal transmission switch (108 is a bidirectional switch and the other 103 to 107 are unidirectional switches), 109 and 110 are ring signal transmission resistors, 111 is a ring response detection circuit, 112 is a ring signal sound source, 113 is a station power supply, 114 is a control circuit of the subscriber circuit (control information output is labor-saving), 115 and 116 are current supply transistors, 117 and 118 are current supply resistors, 119 to 122 are DC bias setting resistors of the current supply transistors 115 and 116, and 123 to Reference numeral 126 is a current detection transistor, 127 is a capacitor for AC high impedance, and 128 is a PBX departure / arrival collision prevention relay (hereinafter abbreviated as G relay).

Further, 315 is a circuit which outputs the loop detection information by detecting the off-hook of the subscriber terminal 101 based on the magnitude of the current sum (IA + IB) from the IA and IB detected by the current detection transistors 125 and 126 and the magnitude of the current sum. Is a call response detection circuit 111
Output (DC current flowing through the resistor 110 + ringing signal current 16Hz
A low-pass filter for extracting only a DC current component from a current proportional to the output), and a circuit 317 for comparing the output of the low-pass filter 316 with a detection threshold ITH for detecting the presence or absence of a ringing response and outputting presence / absence determination information.

In FIG. 2, when the calling signal is transmitted, the current in the direction shown by the solid line (a) flows during the positive phase of the calling signal, and the current of the broken line (b) flows during the negative phase. Then, when the subscriber terminal 101 responds, a DC loop is formed and the call response detection circuit 111 detects the response. At this time, the operating switches are black-colored 106 to 108. The waveform of the detection current I _A on the battery side of the call current supply circuit at this time will be described with reference to FIG. If there is no G relay,
As shown in (a), a half-wave rectified current flows during ringing. On the other hand, after the response, a current having a DC offset due to the DC loop flows. Detection threshold I between the maximum DC I _DCR during this call and the minimum DC current I _DCT after a response
_{If TH} is set, it can be detected. However,
When there is a G relay, as shown in (b), since there is a DC offset IOFF during ringing, the maximum DC I _DCR during ringing is larger than that when there is no G relay in (a). Therefore, the detection threshold I _TH cannot be set. In addition, in (b), the direct current after the reaction is increased from that in (a) by the influence of I _OFF .

Calculating the DC current under each condition, in the case of (a), However, V _R : voltage peak value of ringing signal sound source 112 Z: sum of ringing signal transmission resistances 109, 110, resistance of line 102 and resistance of subscriber terminal 101 ω = 2πf: angular frequency (= 1 / T = 16H _Z ; ringing Signal frequency) t: Time V _E : Voltage of station power supply 113 The upper line of each letter shows the maximum value and the lower line shows the minimum value.

Substituting a typical constant in the actual use state into the equation (1), However, │ Z │ = R ₁₀₉ + R ₁₁₀ + R ₁₀₂ + R ₁₀₁ = 220 × 0.9 + 750 × 0.9 + 0 + 2000 = 2873 (Ω) Substituting the typical constants in the actual use condition into the equation (2), However, V _E = 43 (V) Therefore, I _TH should be set to about 16.2 mA.

Next, in the case of (b), However, I _OFF : DC offset due to PBX start / stop collision prevention relay 128 If you substitute a typical constant in the actual use condition into equation (3), However, ｜ Z ｜ = 2873 (Ω) Substituting a typical constant in the actual use state into the equation (4), However, V _E = 43 (V) || = 2787 (Ω) I _OFF = 7.9 (mA), and I _TH determined by (a) is almost equal to I _DCR ′, resulting in false detection. Therefore, G
Ring signal sending resistor 110 that is hardly affected by relay 118
However, it is necessary to provide a dedicated call response detection circuit, which is an obstacle to simplification of the call response detection circuit. The call current supply circuit section has a function of detecting the currents of both lines in order to perform loop detection in a normal DC power supply state (normal or revers). Before sending the ringing signal, only the switches 105 and 106 are operated to perform a pre-trip test for checking the states of subscribers and subscriber lines.

[Object of the Invention]

An object of the present invention is to provide a method for eliminating the call response detection circuit of the related art and realizing the call response detection with a simple circuit.

[Outline of Invention]

The present invention, in order to detect the call response on the battery side of the call current supply circuit, which could not be realized conventionally by the presence of the PBX outgoing / incoming collision prevention relay, the DC offset current during the pre-trip test performed before the call. By storing the value and changing the DC offset amount to a corrected threshold value when the call response is detected, the call response can be detected on the current side of the call current supply circuit.

Example of Invention

An embodiment of the present invention will be described below with reference to FIG. In FIG. 1, the same components as those in FIG. 2 are designated by the same reference numerals, and 314 is a control circuit of the subscriber circuit according to the present invention. Reference numeral 318 is a DC information storage circuit that stores the value of IA during the pre-trip test.

In FIG. 1, first, only the switches 105 and 106 are operated to perform a pre-trip test in which the switch is placed in the levers state.
At this time, the value of the current IA flowing on the battery side of the call current supply circuit is stored in the pre-trip test DC information storage circuit 318. The value of I _A becomes almost 0 when the PBX departure / arrival collision prevention relay 128 is not provided, and in that case, the value of the DC offset is set. Next, when the call signal transmission is started,
The detection threshold is set by correcting the value of the DC offset stored in the DC information storage circuit 318. That is, from the value of the DC offset stored in the pre-trip test DC information storage circuit 318, the difference (about 4 mA) of the DC component depending on the presence / absence of the G relay, which is indicated by the above values, is calculated, and based on this value The detection threshold value IT in FIG.
H '. Of course, if there is no G relay, the correction is 0, and the detection threshold value shown in FIG.

Storing the DC information during the pre-trip test is easy to realize by using a capacitor or the like, and the control circuit 314
If the processing is digital processing, the information may be stored in the memory and can be realized by an extremely simple circuit.

〔The invention's effect〕

According to the present invention, a circuit with high withstand voltage and high precision dedicated to detecting a ringing response is not required, and the ringing response can be detected by the existing normal current supply circuit, and the circuit can be greatly simplified. The circuit of the added portion can be realized by a circuit having a low withstand voltage, digital processing is possible depending on the configuration of the control circuit, and the increase in the circuit is small.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of a call response detection system according to the present invention, FIG. 2 is a circuit diagram showing an example of a conventional call response detection system, and FIG. 3 is a call current supply circuit when a call response is detected. FIG. 3 is a waveform diagram of a current flowing to the battery side of the battery. 101 …… subscriber terminal, 102 …… subscriber line 103,104 …… normal switch 105,106 …… revers switch 107,108 …… call signal sending switch 109,110 …… call signal sending resistor 112 …… call signal sound source 113 …… Station power supply 115,116 ...... Current supply transistor 117,118 ...... Current supply resistance 119 to 122 ...... Current supply transistor 115,116 DC bias setting resistance 123 to 126 ...... Current detection transistor 127 ...... AC high impedance capacitor 128 ...... PBX departure / arrival collision prevention relay 314 …… Subscriber circuit control circuit 316 …… DC detection low-pass filter 317 …… Comparison for ringing response presence judgment 318 …… Pre-trip test DC information storage circuit

Claims (1)

[Claims] 1. A ringing signal sending method using a wire on the battery side of a call current supplying circuit for sending a ringing signal, when detecting a ringing response by using information from a current detecting circuit of the wire. , A call response detection method characterized in that the call response is detected by correcting the DC information obtained during the state test of the subscriber and the subscriber line before the call.