JPH0322746A - Ring trip circuit - Google Patents

Abstract

PURPOSE:To eliminate the need for a special voltage converting circuit by supplying a driving voltage to a differential amplifier circuit and an amplifier circuit from a power source which is used in a subscriber circuit. CONSTITUTION:A voltage dividing circuit 3 divides a ringer voltage outputted from a ringer power source 2 into a low voltage which is used normally by the subscriber circuit and can drive the differential amplifier circuit 4 and when a subscriber telephone set 1 is in the on-hook or off-hook state, the difference of the divided voltage is outputted to the differential amplifier circuit 4, which is operated with the low voltage. The differential amplifier circuit 4 generates an output according to the level difference of the divided voltage and the output of the differential amplifier circuit 4 is amplified by the amplifier circuit 5 up to a voltage which can be compared with a reference voltage; and a comparing circuit 6 compares the voltage with the reference voltage and outputs a ring trip signal according to the result. Consequently, the need to add a circuit which generates a voltage of -48--24V used normally by the subscriber circuit is eliminated.

Description

[Detailed Description of the Invention] [I Already Required] Regarding a ring trip circuit, the present invention aims to use a power supply normally used in a subscriber circuit as the driving voltage of an operational amplifier, and to output an accurate ring trip signal. In a ring trip circuit in a digital subscriber circuit of a time division exchange, there is a voltage divider circuit connected between a subscriber telephone and a linker power supply that divides the output voltage of the linker power supply, and a voltage divider circuit that divides the output voltage of the linker power supply. A differential amplifier circuit that receives a voltage and calculates the voltage difference between the input voltages, an amplifier circuit that amplifies the output voltage of the differential amplifier circuit to a predetermined level, and a comparison between the output of the amplifier circuit and a reference voltage. and a comparison circuit that outputs a ring trip signal.

[Industrial application field]

The present invention relates to a digital subscriber circuit of a time division exchange,
More specifically, it relates to a ring trip circuit.

[Conventional technology]

A ring trip circuit used in a subscriber circuit of a digital exchange is a circuit that detects whether a subscriber picks up the handset and goes off-hook by ringing when a calling signal is input. The output of this ring trip circuit turns off the relay, for example, and stops the ringing.

5 and 6 are circuit diagrams of conventional ring trip circuits.

First, the ring trip circuit shown in FIG. 5 will be explained. The ring trip circuit shown in the figure includes a linker power supply 8, resistors Rl-R3, resistors Ra, and capacitor Cl (
a linker detection circuit 9 connected to an operational amplifier (operational amplifier) OPI (feedback circuit); and a comparator 1 that compares the output voltage of the operational amplifier OPI with a reference voltage VLh.
It is configured as 0. When a transmission signal is input to the subscriber circuit and, for example, the linker phone aI 8 is operated and ringing is performed, the subscriber lifts up the handset and turns on (off-hook) the hook switch provided on the subscriber telephone 7. In the on-footer state, the subscriber telephone 7 has a composite load consisting of a resistance (R), a capacitive load (C), and an inductive load (L);
), current flows through the resistor R1 connected in series, and a voltage is generated. As a result, a difference occurs in the voltage applied to the human power (normal input and inversion input) of operational amplifier ○P1,
An output voltage corresponding to this voltage difference is output from the operational amplifier OPl to the comparator 10. The comparator 10 compares the input voltage with a predetermined reference voltage Vth. Since the voltage exceeds the reference voltage Vth due to the off-hook, a ring trip signal is output, and based on this ring trip signal, for example, the tone ring relay is turned off to stop ringing. In the above operation, the operating power supply is set to VCC%vt to drive the operational amplifier OPI. Generally, the maximum power supply voltage (difference between + and -) of an operational amplifier is, for example, 36V. However, since the supply voltage Vllm to the linker power supply 8 is normally -48V, in order to keep the voltage applied to the operational amplifier within the power supply voltage, vb is set to -2
It is set to 4V. For this reason, conventional ring trip circuits use -24V instead of the -48V normally used in subscriber circuits.
This -24 square meter is used as the driving voltage (vb or Vcc) of the operational amplifier OPI. Note that the resistor Rl2 shown in FIG. 5 is a resistor for flowing direct current,
Capacitor C2 is for bypassing the alternating current.

Next, the ring trip circuit shown in FIG. 6 will be explained. The ring trip circuit shown in the figure includes resistors R6 to R, connected to the linker power supply 8. , a linker detection circuit 11 including a capacitor C3, a current exchange circuit 12 constituted by a mirror circuit, a current addition circuit 13, an absolute value detection circuit 14, and a comparison circuit 15.

When the receiver recognizes the linker, the receiver takes the subscriber telephone 7 off-hook. Due to this off-hook, the load on the subscriber telephone 7 changes to a resistive load, and the difference in current value between the current I1 flowing through the resistors R6→R7→R8 and the current I2 flowing through the resistors R,→RIG (resistor R6 A voltage difference occurs due to the flowing current, and this voltage difference causes a difference in current], and the current adding circuit 13 combines the current I+ with the current I2 in which the direction of flow of the current I1 is reversed in the current exchange circuit 12.
Add with . Current 1z added by current addition circuit l3
l+ is further output to the absolute value detection circuit l4, and the absolute value current 1■z-r. A resistor R.I is converted into a resistor R.I and constitutes a part of the comparator circuit 15. The output voltage VOUT is generated across the resistor Rll.

The comparator COMI that monitors the comparison circuit l5 compares the output voltage V OUT with the reference voltage Vth, and if the output voltage VOtlτ exceeds the reference voltage VLh due to the off-hook, outputs a ring trip signal and stops the ringing of the tone ring, for example. let

[Problem to be solved by the invention]

In the conventional ring trip circuit described above, the following problems occur.

First, in the ring trip circuit shown in FIG. 5, the voltage Vb*Vcc for driving the operational amplifier OPI is a voltage of, for example, -24cm, which is not normally used in the subscriber circuit, and therefore - is normally used in the subscriber circuit. A voltage of -24V must be generated from a voltage of 48V. Therefore, a circuit must be added to generate this voltage.

In addition, in the ring trip circuit shown in FIG. 6, mirror deviation occurs due to errors in resistors, capacitors, etc. that make up the mirror circuit in the current converter circuit 12 and current adder circuit 13. At the time of calling, an output voltage VOLIT is generated from the absolute value calculation circuit 14, and if the deviation is large, the output voltage VOLIT is generated. U, is comparator CMP
1 reference voltage Vth is exceeded and a ring trip signal is output.

An object of the present invention is to use a power supply normally used in a subscriber circuit as a driving voltage for an operational amplifier, and to output an accurate ring trip signal.

[Means to solve the problem]

FIG. 1 is a block diagram of the principle of the present invention.

A subscriber telephone 1 is a telephone connected to a digital exchange via a subscriber circuit.

The linker power supply 2 is, for example, a power supply for ringing a tone ring or a magnetic bell.

The voltage dividing circuit 3 includes a resistor and a capacitor, and divides the output voltage of the linker power supply 2 when the hook switch in the subscriber telephone 1 is on or off.

The differential amplifier circuit 4 receives the voltage divided by the voltage dividing circuit 3 when the hook switch is on or off, and outputs a voltage according to the difference between the divided voltages.

The amplifier circuit 5 amplifies the output voltage of the differential amplifier circuit 4 to a predetermined level. A comparison circuit 6 compares the output voltage output from the amplifier circuit 5 with a reference voltage, and outputs a ring trip signal when the output voltage exceeds the reference voltage.

(Function) The linker voltage output from the linker power supply 2 is divided by the voltage divider circuit 3 to a voltage that can drive the differential amplifier circuit 4 with the low voltage (±5V) normally used in subscriber circuits.
When the subscriber telephone 1 is on-hook or off-hook, the difference between the divided voltages is output to the differential amplifier circuit 4, and the differential bottle width circuit 4 is operated at a low voltage.

The differential amplifier circuit 4 outputs according to the level difference of the divided voltages manually input, and the output of the differential amplifier circuit 4 is amplified by the amplifier circuit 5 to a voltage that can be compared with the reference voltage VLh. The comparison circuit 6 outputs a ring trip signal based on the comparison result.

The differential amplifier circuit 4 can be operated with a voltage normally used in subscriber circuits, and since the differential amplifier circuit 4 and the amplifier circuit 5 do not have a built-in ξ error circuit, false trips cannot occur due to deviations in the mirror circuit. Nor.

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 2 is an embodiment of the ring trip circuit of the present invention. A series circuit of a linker power supply 2, a resistor RI3, and a subscriber telephone 1 is connected to the power supply Vms (48V).
The other end of subscriber telephone 1 is grounded. Although not shown, the resistor Rl3 and the subscriber telephone 1 are connected through a subscriber line. When subscriber telephone 1 goes off-hook, resistor Rl
3, a current flows and a voltage is generated. Note that this resistance Rl
Since resistor RI3 has a lower resistance than the other resistors Rl4 to Rl9, most of the current flows through this resistor Rl3, and the voltage across the resistor RI3 is approximately determined by the current flowing to the subscriber telephone l.

Resistors Rl and R17 are connected to both ends of resistor RI3, and resistor RI5+ is connected to the other ends of resistor R 1 4 and R I7.
A capacitor is connected to one end of RI8. The other end of the resistor Rl5 is connected to one end of the resistors R'l6 and Rl9 and to the human power (normal input and inverting input) of the operational amplifier OP2.
The other end of the resistor RI6 is grounded, and the other end of the resistor R19 is connected to the output of the operational amplifier ○P2. In addition, resistor R+a and resistor R gate, resistor Rl5 and resistor R18, resistor Rl6 and resistor R1
, have the same resistance value.

A differential amplifier circuit is constructed with operational amplifier OP2 and resistors Rl4 to Rl9, and the resistance values of resistors R+a to Rl9 are r+
4 to rl9, the DC gain G of this differential amplifier is
D is approximately.

On the other hand, the voltage value of the non-inverting input terminal of operational amplifier OP2 is the same as that of the inverting input terminal, and the voltage of the inverting input terminal is the voltage V1 and the resistance R+i (
resistance R ra,
R 15+ R 171 R +a is resistance Rl&+R
Since it has a higher resistance than I9, the voltage at the input terminal of the operational amplifier OP2 is very close to the ground level voltage at the input terminal and the output voltage vI at the input terminal.

Also, for AC voltage, resistor RI4, resistor Rl5, resistor Rl? Since the capacitor C4 is provided at the connection point of the resistor Rll and the resistor Rll, even if an alternating current flows through the resistor RI3 in a linker or the like and an alternating current voltage is generated between both terminals of the resistor Rll, both input terminals of the operational amplifier OP2 are connected. The voltage applied to will be the same.

That is, even if an AC voltage is generated from the linker power supply 2, almost the same voltage will be applied to the operational amplifier ○P2.

In addition, an AC voltage such as a linker is applied, and the AC voltage is applied to the resistor R13.
Even if the current flows to
4), so that substantially the same alternating voltage is applied to both input terminals of the operational amplifier.

The aforementioned resistance R. ~RI6, resistance Rl? The voltage divided by the series circuit of ~RI9 is applied to both input terminals of operational amplifier OP2, but by increasing this voltage division ratio, the voltage applied to both input terminals of operational amplifier OP2 can be increased, for example, between power supply VCC and power supply VEE. voltage, and does not exceed the withstand voltage of the operational amplifier OP2.

On the other hand, as described above, the voltage applied to the input terminal of the operational amplifier OP2 is determined by its output V1. Resistor R17
Since the added value of the resistance value of +Rll is much larger than the resistance value of resistor RI9, its output is small. This output V
, is amplified by the operational amplifier OP3, which operates as a positive-phase amplifier. Resistor R is connected to the inverting input of operational amplifier OP3.
20 and one end of resistor R21 are connected to resistor R2. The other end of the resistor R21 is grounded, and the other end of the resistor R21 is connected to the output of the operational amplifier OP3, and the gain for the series input of the operational amplifier OP3 is the resistor R2. ．． The resistance value of R21 is r 20,
If r 21, then 1 + r 2+/ r 2
It becomes 0, and you can set it to a large value.

That is, as described above, the output voltage (■1) of the operational amplifier (○P2) becomes an AC signal with a small peak value during ringing, as shown by A in FIG. Note that the AC voltage output at this time increases or decreases depending on the value of the capacitor C4. This output voltage v1 is in-phase amplified by the operational amplifier ○P3, and the output voltage v2 shown as B in the figure is output to the comparator CMP2. However, since the reference voltage Vth is higher than this output voltage v2, the ring trip signal is output from the comparator CMP2. Not done.

On the other hand, when the subscriber picks up the handset due to the above-mentioned ringing and the subscriber telephone 1 goes off-hook, the resistance of the telephone 1 becomes only the resistance component (R), and the input voltage to the normal and inverting inputs of the operational amplifier OP2 changes. A difference occurs, and therefore, the voltage level of the output voltage VI during off-hook increases as shown at A' in FIG. Furthermore, when it is amplified to a predetermined level by the operational amplifier OP3 as described above, the output voltage V2 becomes the AC voltage that has reached the reference voltage of the comparator CMP2, as shown by B in the figure. Comparator CMP2 outputs an AC ring trip signal. When this ring trip signal is output,
A supervisory circuit in the subscriber circuit, for example, immediately switches off the relay to stop the ringing and then connects the subscriber telephone l to the telephone line.

As described above, in this embodiment, operational amplifiers OP2 and OP3
Drive the drive voltage (VcC, VEE) at ±5■,
It is sufficient to simply connect the constant voltage power supply of the normally used subscriber circuit.

In this embodiment, the resistor Rl5 and the resistor Rlll are constructed with resistors having the same resistance value, but the resistance value r of the resistor RI5
l5 by changing the resistance 4firsts of the resistor Rl5 in Fig. 4 (
Change the resistance value r to 15' so that the output voltage V2 is equal during idle (idle means on-footer time when no ringing is occurring) and ringing, as shown in the characteristic diagram when the change (rx) is made. As can be seen from the figure, it is possible to increase the voltage level difference between off-hook and ringing, and to achieve an accurate ring trip function that does not cause false detection. That is, by changing the resistance Rl and changing the gains of the normal input and the inverted input, it is possible to increase the difference between the voltage values during ringing and off-hook.

〔Effect of the invention〕

The ring trip circuit of the present invention can supply the driving voltage to the differential amplifier circuit or the amplifier circuit from the power supply used in the subscriber circuit, and does not require a special voltage conversion circuit.

Further, since the above circuit is not required, the cost of the device including the ring trip circuit can be reduced.

Further, since the ring trip circuit of the present invention does not use a mirror circuit, it is possible to prevent the trip due to a ξ error error and to perform an accurate ring trip function.

[Brief explanation of drawings]

Fig. 1 is a diagram of the principle configuration of the present invention, Fig. 2 is a circuit diagram of an embodiment of the present invention, Fig. 3 is an output waveform diagram of the embodiment, and Fig. 4 is when the resistance value of resistor Rl5 is changed. 5 and 6 are conventional circuit diagrams. 1...Subscriber telephone, 2...Linker power supply, 3...Voltage divider circuit, 4...Differential amplifier circuit, 5...Amplifier circuit, 6...Comparison circuit. T force of implementation orgasm 1; anti-sweating month 3rd figure

Claims (1)

[Claims] 1) In a ring trip circuit in a digital subscriber circuit, a voltage divider that is connected between a subscriber telephone (1) and a linker power supply (2) and divides the output voltage of the linker power supply (2). The voltage divided by the circuit (3) and the voltage dividing circuit (3) is input,
A differential amplifier circuit (4) that detects the voltage difference between the input voltages.
an amplifier circuit (5) that amplifies the output voltage of the differential amplifier circuit (4) to a predetermined level; and a comparison circuit (5) that compares the output of the amplifier circuit (5) with a reference voltage and outputs a ring trip signal. 6) A ring trip circuit comprising: 2) The voltage divider circuit is composed of a plurality of resistors, and the resistance value of at least one of the plurality of resistors is set such that the difference between the output voltage during off-hook and the approximately equal output voltage during idling and ringing is maximum. 2. The ring trip circuit according to claim 1, wherein the ring trip circuit is selected such that: