JPS61200760A - Subscriber circuit - Google Patents

Abstract

PURPOSE:To improve the reliability by obtaining a subscriber line interface signal for call reply supervisory of a subscriber from a comparator included in a feeding circuit to use a low-pass filter in common for a response detection circuit thereby decreasing the increase in the hardware. CONSTITUTION:Since subscriber lines 121, 122 are connected to the feeding circuit side by changeover switches 41, 42 during talking, an output of a differential amplifier 8 is zero. On the other hand, at the transmission of a call signal, since the changeover switches 41, 42 open an output of a current source 16, a differential amplifier 15 outputs a prescribed value and a voltage adding a prescribed DC component to an output voltage of the differential amplifier 8 is inputted to a low-pass filter 17. In setting a voltage of a fixed threshold power 11 to a value between a signal peak appearing at an output of the low pass filter 17 before subscriber call reply and a signal peak appearing at subscriber call reply, the polarity is inverted before and after the subscriber reply and a subscriber line interface signal is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a circuit configuration of a subscriber circuit that sends out a calling signal or supplies talking current to a subscriber line.

(Prior Art) FIG. 2 is a block diagram showing an example of a subscriber circuit according to the prior art. In FIG. 2, 1 is a battery, 221',
222 is a feeding coil, 3 is a 2-wire 4-wire conversion circuit,
41 and 42 are changeover switches, 5 is a calling signal source, 6.7 is a limiting resistor, 8 is a differential amplifier, 9 is a low-pass filter, 10 is a comparator, 11 is a fixed threshold power supply, 12
1°122 is a subscriber line.

In FIG. 2, during a call, the subscriber lines 121 and 122 are connected to the feed coils 221 and 22 by the changeover switches 41 and 42.
2, and a 2-wire/4-wire conversion circuit 3, and a subscriber terminal (not shown) is connected to a power supply coil t21.2 from the battery 1.
222. On the other hand, a paging signal sending circuit including a paging signal source 6 is connected to the subscriber lines 121 and 122 at the time of paging signal sending by changeover switches 41 and 42. This causes an alternating current to flow from the calling signal source 5 through the limiting resistor 6, the changeover switch 41, 42, the subscriber line 121, the subscriber terminal (not shown), the subscriber line 122, the limiting resistor 7 and the battery 1. The bell inside the terminal rings due to the signal current. Before the subscriber responds, no DC current flows through the terminal, so the output of the differential amplifier 8 does not include a DC component, so the output of the low-band frequency filter, which includes the frequency band of the calling signal as a stopband, is Never exceed a certain voltage. When the subscriber responds, a DC circuit is formed through the terminal, and the DC voltage drop appearing across the limiting resistor 6 is detected by the differential amplifier 8. Therefore, the output of the low-pass P wave generator 9 continuously becomes a value exceeding a certain voltage. Here, by appropriately determining the fixed threshold power supply 11, the output of the comparator 10 is inverted before and after the subscriber's response, so that the response can be detected.

FIG. 8 is an equivalent circuit diagram of each of the feeding coils 221 and 222 in FIG. 2, where 13 is a resistor with a value of R;
14 is an inductance with a value of L. In order to reduce the error in the terminal impedance synthesized by the two-wire/four-wire conversion circuit 3, the value of the inductance 14 needs to be sufficiently large in the audio band, and is usually set to about 10 Henrys. Further, the value R of the resistance 13 of the feeding coil is usually several hundred ohms.

Figure 4 shows the battery 1 and supply coil 221 in Figure 2.
, 212, 15 is a second differential amplifier with an amplification factor of K, and 16 is a current of a transconductance gm that outputs a current proportional to the input voltage. 17 is a low-pass p-wave generator with a transfer function H, 20 is an adder, and 21 is a second battery with voltage v0.

In Figure 4, the voltage between points 18 and 19 is expressed as v1 current source 1
Letting i be the current flowing through 6, i=gmH(Kv+v0) a e 11111, and the impedance 2 when looking at the communication current supply circuit from point 18.19 can be expressed as follows. Here, by setting the transfer function H to have a low-pass filter characteristic expressed by the following equation, a subscriber circuit equivalent to that shown in FIG. 2 can be constructed.

Then it becomes. Here, the cutoff frequency fc of the low-pass p-wave generator 17 (transfer function H) is as follows. This fcO value needs to be several Hz or less in order to keep the error in the termination impedance below an allowable value. On the other hand, the cutoff frequency of the low-frequency p-wave generator 9 in FIG. 2 is set to several H2 in order to block the alternating current component of the calling signal such as 16 Hz, 20 Hz, etc.

(Problems to be Solved by the Invention) Therefore, the electronic subscriber circuit in which the power supply circuit in Fig. 2 is replaced with the one in Fig. 4 uses a low-band p-wave generator having a cut-off frequency as low as that in Fig. 4. The disadvantage of requiring two devices is that the amount of hardware increases.

An object of the present invention is to eliminate the above-mentioned drawbacks by also using a low-frequency p-wave device that synthesizes the equivalent inductance of the power supply circuit for the calling response detection circuit, and to achieve high reliability with less increase in the amount of node wear. Its purpose is to provide subscriber circuits.

(Means for Solving the Problems) A subscriber circuit according to the present invention includes a calling signal sending circuit, a power supply circuit, and a switch, and the power supply circuit includes a subscriber line interface signal for monitoring a call response of a subscriber. The comparator is configured to obtain the result from the comparator.

The ringing signal sending circuit comprises current sensing means including a first differential amplifier for applying a ringing signal voltage to the subscriber line.

The power supply circuit includes a second circuit for detecting the line voltage of the subscriber line.
a differential amplifier, an adder for calculating the sum of the output of the second differential amplifier and the output of the current detection means, and a low frequency door filter for creating a communication current to be supplied to the subscriber from the output of the adder. The communication current supply means comprises a current source, and a comparator ρ for comparing the output signal of the low-pass P wave generator with a threshold value.

The switch is used to select either the calling signal sending circuit or the power feeding circuit and connect it to the subscriber line.

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

FIG. 1 is a block diagram illustrating one embodiment of a subscriber circuit according to the present invention. In Figure 1, 1 is a battery, 41.4
2 is a changeover switch, 5 is a calling signal source, and 6.
7 is a limiting resistor, 8 is a differential amplifier, 10 is a comparator, 11 is a fixed threshold power supply, 15 is a second differential amplifier, 16
is a current source, 17 is a low-frequency p-wave generator, 20 is an adder, and 21 is a second battery.

In FIG. 1, the output of the differential amplifier 8 that detects the voltage drop appearing across the limiting resistor of the calling signal sending circuit and the output of the second differential amplifier 15 that detects the line voltage of the subscriber line are The signals are added by the adder 20 and input to the low-pass P-wave unit 17 .

In FIG. 1, during a call, the subscriber lines 121 and 122 are connected to the power supply circuit side by the changeover switches 41 and 42, so the output of the differential amplifier 8 becomes zero. Therefore, the power supply circuit exhibits characteristics similar to the electronic circuit of the power supply coil shown in FIG. On the other hand, when the calling signal is sent, the output of the current source 16 is opened by the changeover switches 41 and 42, so the active elements constituting the current source 16 are saturated and output a constant voltage. Therefore, the second differential amplifier 1
6 outputs a constant value, and the low-band F-wave generator 17 outputs the voltage at the peak value of the signal that appears at the output of the low-band F-wave generator 17 before the subscriber's call response, and the voltage that appears when the subscriber responds to the call. By setting the comparator 10 to be between the peak value of the signal
As in the case of FIG. 2, the output of is inverted before and after the subscriber's response.

Thereby, a subscriber line interface signal for monitoring the subscriber's call response can be obtained.

(Effects of the Invention) As explained above, the present invention reduces the increase in hardware amount by sharing the low-pass filter that synthesizes the equivalent inductance of the power supply circuit with the paging response detection circuit.
This has the advantage that a highly reliable circuit configuration can be easily realized using a semiconductor electronic circuit system.

[Brief explanation of the drawing]

FIG. 1 is a block diagram illustrating one embodiment of a subscriber circuit according to the present invention. FIG. 2 is a block diagram showing an example of a subscriber circuit according to the prior art. FIG. 8 is an equivalent circuit diagram of the feeding coil shown in FIG. 2. FIG. 4 is a block diagram showing an example in which the power supply circuit shown in FIG. 2, which includes a battery and a power supply coil, is converted into a semiconductor electronic circuit. 1.11.21-Working/Battery 221.222--Feeding coil S...2-wire 4-wire switching circuit 41.42--Selector switch 5...Calling signal source 6 .7...Resistor 8.15-...Differential amplifier 9.17...Low frequency door filter 10...Comparator 121.122...Subscriber line 16. ... Constant current source 18.19 ... Input point 20 ... Adder

Claims (1)

[Claims] a paging signal sending circuit comprising current detection means including a first differential amplifier for applying a paging signal voltage to the subscriber line and detecting a response signal; and a paging signal sending circuit for detecting the line voltage of the subscriber line. a second differential amplifier; an adder for determining the sum of the output of the second differential amplifier and the output of the current detection means; a talk current to be supplied to the subscriber line from the output signal of the adder; a calling current supply means consisting of a low-pass filter and a current source for generating a calling signal; a power feeding circuit consisting of a comparator for comparing the output signal of the low-pass filter with a threshold value; and the calling signal sending circuit. , or a switch for selecting one of the power supply circuits and connecting it to the subscriber line, and transmitting a subscriber line interface signal for monitoring a call response of a subscriber to the comparison circuit included in the power supply circuit. A subscriber circuit characterized in that the subscriber circuit is configured to obtain information from a receiver.