JPS59125158A - Detecting system of push of earth button - Google Patents

Abstract

PURPOSE:To detect stably the push of an earth button by means of a subscriber circuit which holds tthe current value at a fixed level at the side of the line A and regardless of the length of the line, by switching the voltage monitor to the current monitor at the side of the line B for the push of the earth button. CONSTITUTION:The current is converted into the voltage by a microresistance 204 and an operational amplifier 205, and this voltage is compared with the reference value 206 by a comparator 207. At the same time, photocouplers 208 and 209 are provided. The output of the 209 is set at L level while a current is flowing toward a line A. The output of the 207 is set at L level when the current of a line B is less than the value 206, and the output 211 is set at H level. Thus it is considered that an earth button is pushed. Therefore the push of the earh button is discriminated if the current flowing to the line B is set at <=1/2 current value of the line A since the resistance value is generally equal between resistances 106 and 107 when the line has a long length.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a subscriber circuit of an electronic exchange, and more particularly to a method for detecting press of a ground button in a subscriber circuit accommodating a telephone equipped with a ground button.

Conventionally, detection of pressing of the ground button ψ of a telephone equipped with a ground button was carried out based on the potential on the B line side. Part 1 below
This will be explained using figures. 101 is a telephone with a ground button, 1
02 is a line, and 103 is a subscriber circuit.

104 is a so-called earth button, and by pressing this button, the A line (or B line depending on the wiring construction method)
The potential of is fixed at ground potential. 105° and 106 represent the direct current resistance of the line. Furthermore, 107 indicates the grounding resistance of the earth. Coils 108 and 109 have high impedance in terms of alternating current, and are used to supply direct current to the telephone. 110 is the /S hybrid circuit, and the filling machine 101
Used to send and receive all audio to and from. 111 is a controller for monitoring the B line potential, and when the B line potential exceeds the reference potential applied to the terminal 112, the output 113 is output.
becomes low level. 114 and 115 form a photocoupler, and when a current flows to the A line side, the output of the photocoupler 115 becomes a low level. Reference numeral 116 denotes a gate circuit that determines that the earth button has been pressed when a current is flowing to the A line side and the output 113 becomes low level, and outputs a high level signal to the output 117.

Here, the DC resistance values of resistors 105, 106, 107, 108, and 109 are respectively RA + RB and Rc r
If Rc r RD, when the distance between the telephone and the subscriber circuit is long, RA = RB = RG, and the reference potential to be applied to the terminal 112 is as follows.

However, with this method, it cannot be used in a subscriber circuit that supplies a constant current from the A line side because RC changes significantly, and it also depends heavily on RA, making it difficult to use as a reference potential. There were drawbacks. .

The purpose of the present invention is to enable stable detection regardless of the length of the line with a subscriber circuit that maintains the incoming current value constant by changing the pressing of the earth button from monitoring the voltage on the B line side to monitoring the current. An object of the present invention is to provide a method for detecting when a next earth button is pressed.

The earth button press detection method of the present invention includes a constant current circuit that controls the DC current in one line of the subscriber line (hereinafter referred to as A) to a constant value, and a DC current in the other line of the subscriber line (hereinafter referred to as color). It includes a current detection circuit that monitors the current value and a subscriber loop monitoring circuit that monitors the subscriber's loop, and the subscriber loop monitoring circuit detects the formation of the subscriber's loop, and the current detection circuit detects the direct current of the subscriber. It is characterized in that it is determined that the earth button has been pressed when it is detected that the current value has become less than a preset value smaller than the DC current value of the instep.

Next, the present invention will be explained with reference to the drawings.

FIG. 2 is a circuit diagram showing a first embodiment of the present invention. 2
01 is a subscriber circuit, a 202-digit constant current circuit, and its -
The means for realizing this is shown in Figure 3. 203゜212 is a coil that realizes high impedance, 204 is a minute resistance,
205 is an operational amplifier. The current is converted to voltage using a microresistance 204 and an operational amplifier 205, and a comparator 207
is compared with the reference value 206. 208 and 209 constitute a hotter and a knobler, and when a current is flowing to the A line side, the output of the hotter and sobbler 209 becomes a low level.

Further, when the current in the B line falls below the reference value 206, the output of the comparator 207 becomes a low level, and as a result, the output 211 of the gate circuit 210 becomes a NO level.

This is considered to mean that the ground button has been pressed.

Now let the DC resistance values of resistors 105, 106, 107, and 203 be RAIRBIRG and RE, respectively, and resistors 105 and 1
Assuming that the DC currents flowing through 06 are IA and IB, respectively, the reference value applied to the input 206 of the comparator 207 may be set to the output voltage value of the operational amplifier 205 when the DC current 2B becomes .

Generally, when the line is long, the DC resistance value RB of the resistor 106
and the DC resistance value R of the resistor 107 are equal, and the resistor 20
The DC resistance value RE of resistor 106 is normally designed to be a smaller value than the DC resistance value RB of resistor 106. That is, in general, it can be determined that the earth button has been pressed when the DC current value flowing on the A line side is less than about half of the value of the DC current on the A line side, as shown by Bm'f: 11B-tiIA. Note that by matching the current flowing through the resistor 105 with the constant current setting value of the constant current circuit 202, the reference value 206 can be set to a fixed value.

FIG. 4 is a circuit diagram showing a second embodiment of the present invention. 4
0] is a subscriber circuit, 402 and 403 are high impedance circuits in terms of current transformation, and 404 is a hybrid circuit. 406 is a central control circuit, 407 and 408 are Hall elements, 409 and 410 are operational amplifiers, 411 and 412 are analog-digital conversion circuits, and 405 is a programmable DC power supply. The central control circuit 406 controls the Hall collector 407 so that the DC current of the %A line becomes a specified value (for example, 35 mA). The programmable DC power supply 40 is monitored by the operational amplifier 409 and the analog-to-digital conversion circuit 411.
Adjust 5. After completing the adjustment, the central control circuit 406. is the Hall element 408. Podium width instrument 410. The analog-to-digital conversion circuit 4121 measures the B line current value, and when the value is less than or equal to the A line current value, it is determined that the ground button has been pressed.

An example of a programmable DC power supply is shown in FIG. 5
02 is a digital-to-analog converter that drives the main transistor 501, thereby making it possible to set the emitter potential of 501 to an arbitrary value.

In the above description, it goes without saying that even if the A line and the Bm gold are exchanged, the operation will be exactly the same.

Further, the constant current circuit, current detection circuit, etc. are not limited to the above embodiments.

As described above, the present invention can accurately detect pressing of the ground button regardless of the line length.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an example of a conventional earth button detection circuit, and FIG. 21d is a circuit diagram showing a first embodiment of the present invention.
3 is a circuit diagram showing an example of the constant current circuit shown in FIG. 2, FIG. 4 is a circuit diagram showing a second embodiment of the present invention, and FIG. 5 is a circuit diagram showing an example of the constant current circuit shown in FIG. 201... subscriber circuit, 2o2... constant current circuit, 204... minute resistance, 205...
... Current voltage conversion circuit, 207 ... Comparator, 401 ... Subscriber circuit, 405 ...
... Programmable DC power supply, 406 ... Central control circuit, 501 ... Control transistor, 5
o2...1 Izotal analog converter. Figure 1 Figure 3

Claims (1)

[Claims] In an electronic exchange that uses a telephone with a ground button, the subscriber circuit has a constant current circuit that controls the DC current on one line of the subscriber line (hereinafter referred to as A) to a constant value, and the other line of the subscriber line (hereinafter referred to as A).
A current detection circuit that monitors the DC current value (hereinafter referred to as B) and a subscriber loop monitoring circuit that monitors the subscriber's loop are provided, and when the subscriber loop monitoring circuit detects the formation of a subscriber's loop and the An earth button press detection method that determines that the earth button has been pressed when the detection circuit detects that the DC current value of B is less than a preset value that is smaller than the DC current value of A.