JPS61113348A - Subscriber circuit - Google Patents

Abstract

PURPOSE:To ensure non-ringing calling by disconnecting a capacitor from a feedback path and connecting it to the feedback path after polarity inversion while a switch is being interrupted in a digital exchange. CONSTITUTION:In closing a switch 22 for non-ringing call to a telemeter terminal device 24, a load current IL is fed from a feeding circuit 15. Then in zeroing a voltage Vab to stop the supply of the load current IL, since the capacitor 14 is connected to the feedback circuit via a diode 26 and a resistor 5, the load current IL is not controlled. Further, in inputting a non-ringing call signal NRS to a current mirror 11 while being superimposed on the control current I1 for polarity inversion, no discharge current except a current I3 is inputted to a current mirror 10, the prescribed control current I1 is outputted and the non-ringing signal is received immediately.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a subscriber circuit of a digital exchange that is capable of quickly transmitting a silent ringing signal to a subscriber line.

In digital exchanges, attempts have been made to collect the amount of water, gas, etc. used from within the home via the subscriber line. In such a case, it is necessary to activate the telemeter terminal attached to the telephone without ringing the ringing bell of the telephone connected to the subscriber line. After reversing the polarity,
Ringless calling methods have been attempted, such as transmitting a predetermined voice band frequency signal (for example, 2080 Hz).

In order to prevent the telephone bell from ringing due to a transient phenomenon during polarity reversal, consideration has been given to temporarily stopping the supply of load current and then reversing the polarity and restarting the supply.

[Conventional technology]

FIG. 2 is a diagram showing an example of a conventional subscriber circuit, and FIG. 3 is a diagram showing an example of a silent call process to which the present invention is applied.

In FIG. 2, the subscriber circuit includes transistors 1 and 2.
, resistors 3.4 and 5, amplifiers 6 to 9, current mirrors 10 to 12, converter 13, and capacitor 14. Switches 17 to 20 for reversing the polarity and the power supply circuit 1 in the case of a silent call.
5 is a loop resistor 21 that compensates for the operable load current IL.
and a switch 22. A power supply circuit 15 supplies a load current IL proportional to a control current 11 output from a current mirror 10 to transistors 1 and 2 and a resistor 3.
and 4. Furthermore, amplifiers 8 and 9 monitor voltages Va and vb generated across transistor 1 and resistor 3 or transistor 2 and resistor 4, respectively, due to load current IL, and transmit the voltages to converter 13. converter 1
3 sums up the transmitted voltages Va and vb and then converts it into a feedback current 2 proportional to the summed voltage value and inputs it to the current mirror 12. The current mirror 12 outputs a current 3 proportional to the manually applied feedback current I2, and inputs it to the current mirror 10 via the resistor 5. The current mirror 0 outputs a control current 11 proportional to the input current T3. As described above, the control current (1) and the feedback current I2 are linked by the feedback path passing through the current mirrors 12 and 10, thereby causing the power supply circuit 5 to perform a constant resistance power supply operation. Note that the capacitor 14 prevents feedback operation for AC signals.

In FIGS. 2 and 3, in a no-call state, switches 17 and 18 are in a conductive state, switches 19, 20 and 22 are in a cut-off state, and the load current I from the power supply circuit 15 is
L is not supplied, and the voltage Vab between the A and B terminals becomes equal to the power supply voltage v1.

In order to make a silent call to the telemeter terminal 24 in this state, the switch 22 is made conductive at time t1.

As a result, the load current IL supplied from the power supply circuit 15 is
The voltage Vab between the A and B terminals becomes a voltage v2 lower than the power supply voltage ■1. Also, the control current I
I, the feedback current I2, and the current I3 are maintained at steady values corresponding to the load current IL flowing through the loop resistor 21.

The capacitor 14 is charged to a voltage 3 corresponding to the voltage drop due to the current 3 of the resistor 5 and the current mirror 10.

Next, in order to stop supplying the load current IL, at time t2, the switches 17 and 18 are turned off, and at the same time, the switch 23 in the power supply circuit 15 is turned on, and the voltage Vab between terminals A and B is set to 0. .

Even in this state, a current (so-called off-drive current) to turn off the switch 17 flows through the transistor 1 and the resistor 3, and the voltage Va detected by the amplifier 8 becomes approximately equal to the power supply voltage 1. As a result, the converter 13 increases the feedback current 2 input to the current mirror 12 in proportion to the voltage v1, and the current I3 output from the current mirror 12 also increases from its steady value. Capacitor 14 carries current I3
is further charged by the increase in voltage, and the terminal voltage Vc becomes voltage 73.
(solid line state in FIG. 3).

Furthermore, the control current 11 output from the rent mirror 10 flows through the switch 23 and does not control the load current IL.

Furthermore, for polarity reversal, switches 19 and 2 are activated at time t3.
0 is made conductive, and the switch 23 in the power supply circuit 15 is made to be in the recovery state.At the same time, a non-ring ringing signal NR3 of a predetermined frequency (for example, 2080 Hz) is superimposed on the control current 1 and input to the current mirror 11. As a result, power supply circuit 1
The load current IL supplied from A 5 flows through the switch 20, the loop resistor 21, the switches 22 and 19, and
The voltage Vab between the terminals B and B is a voltage 4 whose polarity is inverted from the voltage V2. Under such conditions, the current I3 is at the time tl
to a steady value similar to L2, but capacitor 14
continues discharging until the terminal voltage Vc becomes approximately the same as the voltage V3 from time tl to t2. As a result, the discharge current from the capacitor 14 is input together with the current I3 to the current mirror 10, and the control current 1 is increased from the steady value by a current value corresponding to the discharge current. As a result, transistors 1 and 2 are supplied with increased base current and become saturated, making it impossible to transmit the input non-ring ring signal NRS to telemeter terminal 24. Eventually capacitor 1
When the terminal voltage Vc of the transistor 4 reaches the same level as the voltage 3, the discharge from the capacitor 14 stops, the control current 11 output from the current mirror 10 also decreases to a steady value, and the transistor 1
and 2 are in a non-saturated state, and the no-ring ringing signal NR3 can be transmitted to the telemeter terminal 24.

At the telemeter terminal 24, the no-ring ring signal NR3 is required to arrive within a predetermined period after the polarity of the load current IL supplied from the subscriber circuit is reversed, but only during the discharge period of the capacitor 14. Non-ringing call signal N
The sending of R3 will be delayed.

[Problem that the invention seeks to solve]

As is clear from the above explanation, in some conventional subscriber circuits, the excess charge that is stored in the capacitor while the load current is in a no-current state is discharged when the polarity of the load current is reversed, and the There was a risk that the power supply circuit would become saturated due to the current), causing a delay in sending out the silent ring signal.

[Means for solving problems]

The problem is that the system has a feedback path that monitors the voltage drop in the power supply circuit due to the load current supplied to the subscriber line and controls the load current based on the voltage drop, and an AC blocking capacitor is added to the feedback path. and a subscriber circuit comprising a switch for reversing the polarity of a load current to the subscriber line, wherein the capacitor is connected to the feedback path and charged while a predetermined load current is supplied before the polarity is reversed, and the switch The present invention is characterized in that the capacitor is disconnected from the feedback path to maintain a charged state while the circuit is in a cut-off state, and the capacitor is connected to the feedback path again after polarity reversal.

[Effect]

That is, according to the present invention, the capacitor is disconnected from the feedback path while the supply of load current is stopped, and after the polarity of the load current is reversed, it is connected to the feedback path again in the charged state before the supply is stopped. There is no longer any risk of being charged with any extra charge during the state. ...: [Embodiment] FIG. 1 is a diagram showing a subscriber circuit according to an embodiment of the present invention. Note that the same reference numerals refer to the same objects throughout the plan. In FIG. 1, a switch 25 and a diode 26 are provided at a portion connecting the capacitor 14 to the feedback path via the current mirrors 12 and 10.

In FIGS. 1 and 3, when the switch 22 is turned on at time t1 in order to make a silent call to the telemeter terminal 24, the power supply circuit 15 is turned on as in FIG.
The load current IL supplied from the terminal flows through the switch 18.22, the loop resistor 21, and the switch 17, and the voltage Vab between the A and B terminals becomes the voltage 2. Further, the control current 11, the feedback current (2) and the current I3 are maintained at steady values corresponding to the load current IL flowing through the loop resistor 21, and the capacitor 14 is charged to the voltage (3) by the current (2).

Next, in order to stop supplying the load current IL, at time t2, the switches 17 and 18 are turned off, and at the same time, the switches 23 and 25I in the power supply circuit 15 are turned on.
Let O be the voltage Vab between the A and B terminals. Even in this state, the off-drive current flows through the transistor l and the resistor 3, and the voltage Va detected by the amplifier 8 is approximately the power supply voltage v.
becomes equal to 1. As a result, the converter 13 increases the feedback current (2) applied to the current mirror 12 in proportion to the voltage v1. As a result, the current mirror 12 outputs a current I
3 also increases from the steady value, but since the capacitor 14 is connected to the feedback path via the diode 26 and the resistor 5,
There is no further charging due to the increase in current 3, and the terminal voltage Vc remains at voltage 3 (as indicated by the dotted line in FIG. 3). Furthermore, the control current 11 output from the rent mirror 10 flows through the switch 23 and does not control the load current IL.

Furthermore, for polarity reversal, switches 19 and 2 are activated at time L3.
0 is in a conductive state, switches 23 and 25 in the power supply circuit 15 are in a restored state, and at the same time, the current mirror 11 is turned on.
Then, the non-ring ringing signal NR3 is superimposed on the control current 11 and manually inputted. As a result, the load current I supplied from the power supply circuit 15
L flows through switch 20, loop resistor 21, switches 22 and 19, and voltage Vab between A and B terminals
becomes voltage V4, which is the polarity inversion of voltage (2). In such a state, the current 3 decreases to a steady-state value similar to the time tl to t2. The capacitor 14 is directly connected to the feedback path again, but since the terminal voltage Vc maintains the voltage ■3, no discharge current other than the current ■3 is input to the current mirror 10, and the predetermined value is A current 11 is output. As a result, transistors 1 and 2 operate in a non-saturated state immediately after time t3, and the input non-ringing ring signal N
R8 is immediately transmitted to the telemeter terminal 24.

As is clear from the above explanation, according to the present embodiment, the telemeter terminal 24 receives the load current I supplied from the subscriber circuit.
After the polarity of L is reversed, the non-ring ring signal NR3 is immediately received, and normal activation becomes possible.

Note that FIG. 1 is only one embodiment of the present invention, and the configuration of the subscriber circuit, for example, is not limited to that shown in the figure, and many other modifications may be considered, but any In this case, the effects of the present invention remain the same.

〔Effect of the invention〕

As described above, according to the present invention, even when the polarity of the load current is reversed through a no-current state, the power supply circuit can immediately transmit a silent ringing signal, and the silent ringing operation can be reliably carried out.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a subscriber circuit according to an embodiment of the present invention;
FIG. 2 is a diagram showing an example of a conventional subscriber circuit, and FIG. 3 is a diagram showing an example of a silent call process to which the present invention is applied. In the figure, 1 and 2 are transistors, 3.4 and 5 are resistors, 6 to 9 are amplifiers, 10 to 12 are current mirrors, 13 is a converter, 14 is a capacitor, 15 is a power supply/circuit, and 16 is a subscriber line. , 17 to 20, 22, 23 and 25 are switches, 21 is a loop resistor, 24 is a telemeter terminal, 26 is a diode, 11 is a control current, I2 is a feedback current, I3 is a current, IL is a load current, NR3 is a non-ringing Call signal, Vl is power supply voltage, V2 to v4, Va, v
b, , vab and Vc represent voltages.

Claims (1)

[Claims] The subscriber line has a feedback path that monitors the voltage drop in the power supply circuit due to the load current supplied to the subscriber line and controls the load current based on the voltage drop, and an AC blocking capacitor is added to the feedback path. In a subscriber circuit equipped with a switch for reversing the polarity of a load current, the capacitor is connected to the feedback path and charged in a state where a predetermined load current is supplied before the polarity is reversed, and the switch is placed in a cut-off state. A subscriber circuit characterized in that the capacitor is disconnected from the feedback path for a period of time to maintain a charged state, and after polarity reversal, the capacitor is connected to the feedback path again.