JPH07131547A - No-ringing terminal analog front end - Google Patents

Abstract

PURPOSE:To prevent the mistrip of a switching device by eliminating the rush current that is generated at the time of reception of the bell signal of a no- ringing terminal analog front end and also preventing the positive-negative asymmetric current occurring on a transmission line. CONSTITUTION:A control signal generating circuit 80 generates a reset signal and a drive signal when a bell signal is received. The reset signal is sent to a reset signal input terminal 45 of a polarity inversion detecting circuit 40B via a charge accumulating circuit 120. Thus the output current of the circuit 40B is reset by the reset signal. When reception of the bell signal is started, the output of the circuit 40B is delayed by a delay circuit 130 and sent to a Miller integrator circuit 110. In this case, however, the drive signal first drives a switch means 140 to turn off the circuit 110. Meanwhile a diode 114 and a high resistance 115 contained in the circuit 110 increase the impedance that is viewed at the side of a Miller capacitor.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a no-ringing terminal analog front end for remote monitoring of instruments and the like by using a telephone line, and in particular, an erroneous trip on the side of the exchange when receiving a bell signal sent from the exchange. The present invention relates to a circuit configuration for preventing.

[0002]

2. Description of the Related Art FIG. 2 is a circuit diagram showing a configuration example of a conventional no-ringing terminal analog front end. A no-ringing terminal analog front end 20 is connected to the pair of transmission lines L1 and L2 extending from the exchange 10. The exchange 10 has a switch 11 connected to the transmission line L1, and the switch 11 is connected to, for example, a −48V battery V _BB via a current limiting resistor 12. The switch 13 is connected to the transmission line L2, to the switch 13, a current limiting resistor 14, and through the ring trip detection resistor 15, for example 16H _Z,
A bell signal source 16 of 75 Vr.ms is connected. The ring trip detection resistor 15 has a ring trip circuit 1
7 are connected in parallel. Although not shown, the exchange 10 is also provided with other circuits such as a polarity reversing circuit. The no-ringing terminal analog front end 20 includes a rectifier circuit 30, a polarity reversal detection circuit 40 that detects a polarity reversal state on the transmission lines L1 and L2, a bell signal detection circuit 50 that detects a bell signal from the exchange 10, and a termination circuit. 60 is provided. The first and second input terminals 31 and 32 of the rectifier circuit 30 and the input terminal 41 of the polarity inversion detection circuit 40,
42 is connected to the pair of transmission lines L1 and L2.
The polarity inversion detection circuit 40 has a holding circuit 43 that holds the detection result. Between the positive side output terminal 33 and the negative side output terminal 34 of the rectifier circuit 30, the input terminals 51 and 52 of the bell signal detection circuit 50 and the termination circuit 60 are arranged in parallel.
The input terminal of is connected.

The termination circuit 60 includes a primary winding 61a of a transformer 61 for transmitting an AC signal, a capacitor 62 for blocking a DC current, and a switch element for forming a DC loop (for example,
Transistor) 63, which are connected in series. Positive side output terminal 33 of rectifier circuit 30 and transistor 6
A resistor 64 of, for example, several KΩ to several tens KΩ for forming a DC loop current required at the time of no-ringing communication is connected between the third electrode and the collector serving as the first electrode. Between the collector / control electrode base of the transistor 63,
The mirror capacitor 65 is connected. The transistor 63 and the Miller capacitor 65 form a Miller integrating circuit. A resistor 66 for stabilizing the operation is connected between the base of the transistor 63 and the emitter as the second electrode,
Further, its base is connected to the output terminal 44 of the polarity inversion detection circuit 40. Further, output terminals 67 and 68 for AC signals are connected to the secondary winding 61b of the transformer 61, and transmission / reception with a modem or the like connected to the outside is performed via the output terminals 67 and 68. Has become.

FIG. 3 shows the output voltage V of the rectifier circuit 30 of FIG.
30 and the bell signal current BI flowing through the transmission lines L1 and L2
It is a figure showing the waveform of. The operation of FIG. 2 will be described with reference to this figure. In FIG. 2, when polarity reversal is performed on the transmission lines L1 and L2 from a polarity reversal circuit (not shown) provided in the exchange 10, the polarity reversal detection circuit 40 in the no-ringing terminal analog front end 20 detects this. , And outputs the detection result to the output terminal 44. This output drives the base of the transistor 63 to which the mirror capacitor 65 is added, so that the loop current required for communication causes a polarity reversal circuit (not shown) in the exchange 10 → transmission line L1 → the input terminal 31 of the rectifier circuit 30 → Positive side output terminal 33 of rectifier circuit 30 → resistor 64 for forming DC loop current →
Transistor 63 → Negative output terminal 34 of rectifier circuit 30 →
Input terminal 32 of rectifier circuit 30 → transmission line L2 → switch 1
It flows to the route of the polarity inverting circuit (not shown) within 0 while changing smoothly. The flow of the loop current while changing smoothly is due to the so-called Miller effect due to the Miller capacitor 65 added between the collector and the base of the transistor 63. If the mirror capacitor 65 is not provided, the transistor 63 is rapidly turned on, so that the transformer 61 having a transient impedance lower than that of the resistor 64 for forming a DC loop current is transiently used.
Since a current flows from the capacitor 62 to the capacitor 62, a large pulsed current instantaneously flows through the transmission lines L1 and L2, causing the exchange 10 to malfunction (for example, to detect an erroneous call). Therefore, the mirror capacitor 65 is an indispensable element. As described above, the communication state of the no-ringing terminal analog front end 20 is set.

[0005]

However, the conventional no-ringing terminal analog front end has the following problems. When a bell signal is sent from the exchange 10 when calling a telephone terminal, the bell signal current B
I is the bell signal source 16 → the ring trip detection resistor 15
→ Current limiting resistor 14 → Switch 13 → Transmission line L2 →
Input terminal 32 of rectifier circuit 30 → positive output terminal 33 of rectifier circuit 30 → primary winding 61a of transformer 61 → capacitor 62 (also shunting resistor 64 for forming DC loop current) → capacitor 65 → base of transistor 63 → Simultaneously with the emitter of the transistor 63, it is turned on when the transistor 63 exceeds the operation threshold, so that the transistor 6 is temporarily turned on.
3 collector → emitter → negative side output terminal 34 of rectifier circuit 30 → input terminal 31 of rectifier circuit 30 → transmission line L1 → switch 11 in switch 10 → current limiting resistor 12 → battery V _BB → ground The capacitor 65 temporarily drives the base of the transistor 63. Output voltage V
The transistor 63 is turned on (point Q in FIG. 3) at a certain value of the waveform of 30 (point P in FIG. 3), that is, the operation threshold value of the circuit composed of the transistor 63, the capacitor 65, and the operation stabilization resistor 66. A current of several tens of mA will flow.

In order to solve the above problems, the applicant of the present application has previously made the following proposal in Japanese Patent Application No. 4-231123 (hereinafter referred to as the above proposal). The technique proposed above has a first input terminal, a second input terminal, a positive output terminal, and a negative output terminal, and the first input terminal and the second input terminal are connected to a pair of transmission lines extending from the exchange. A rectifier circuit, a polarity reversal detection circuit connected to the transmission line for detecting a polarity reversal state on the transmission line, and connected in parallel between the positive output terminal and the negative output terminal of the rectifier circuit, Bell signal detection circuit that detects the bell signal from the line,
A terminating circuit connected in parallel between the positive side output terminal and the negative side output terminal of the rectifier circuit, wherein the terminating circuit has a first output according to an output of the polarity reversal detection circuit applied to a control electrode.
A no-ringing terminal analog having a switch element for controlling on / off between a second electrode and a second electrode to form a DC loop current required for no-ringing communication, and a mirror capacitor connected between the control electrode of the switch element and the first electrode Switch means is provided at the front end. The switch means is connected between the control electrode and the second electrode of the switch element and has a function of being turned on by the output of the bell signal detection circuit to turn the switch element off. Since the previous proposal configured the no-ringing terminal analog front end as described above, when the bell signal is sent from the exchange through the transmission line, the bell signal detection circuit detects it and synchronizes with the bell signal. Then, the switch means is turned on. As a result, the bell signal current input from the mirror capacitor to the control electrode of the switch element is bypassed by the switch means, the switch element is forcibly turned off, and an erroneous trip is prevented.

However, the above proposal also has the following problems. FIG. 4 is a circuit diagram showing one configuration example of the previously proposed no-ringing terminal analog front end. A no-ringing terminal analog front end 20A is connected to the pair of transmission lines L1 and L2 extending from the exchange 10. The exchange 10 has the same configuration as that of FIG.
0 is a switch 11 connected to the transmission line L1, a current limiting resistor 12, a −48V battery V _BB, and a transmission line L.
A switch 13 connected in two, a current limiting resistor 14,
The ring trip detection resistor 15 and, for example, 16H _Z , 7
And a bell signal source 16 of 5 Vr.ms. A ring trip circuit 17 is connected in parallel to the ring trip detection resistor 15. Although not shown, the exchange 10 is also provided with other circuits such as a polarity reversing circuit. The no-ringing terminal analog front end 20A is provided with a rectifier circuit 30, a polarity reversal detection circuit 40, and a bell signal detection circuit 50 similar to those in FIG. 2, and these are the transmission lines L1 and L2 and the rectification circuit 30 as in FIG. Positive output terminal 3
3, and is connected between the negative output terminals 34. Termination circuit 6
Similarly to FIG. 2, 0 also has a primary winding 61a of a transformer 61 for AC signal transmission, a DC current blocking capacitor 62, and a DC loop forming transistor 63, which are connected in series. . Positive output terminal 3 of rectifier circuit 30
A resistor 64 of, for example, several KΩ to several tens of KΩ for forming a DC loop current required at the time of no ringing communication is connected between 3 and the collector of the transistor 63. The mirror capacitor 6 is provided between the collector and the base of the transistor 63.
5 are connected. A resistor 66 for stabilizing the operation is connected between the base and the emitter of the transistor 63, and the base of the resistor 63 is an output terminal 44 of the polarity inversion detection circuit 40.
It is connected to the. Unlike the case of FIG. 2, the no-ringing terminal analog front end 20A is connected between the base and the emitter of the transistor 63, operates based on the output of the bell signal detection circuit, and is provided with switch means 70 for turning off the transistor 63. The switch means 70 is
A transistor 71 in which the output of the bell signal detection circuit is connected to the base, and a collector and an emitter are respectively connected between the base and the emitter of the transistor 63, and the transistor 7
1 has an operation stabilizing resistance 72.

The normal communication state setting operation in the no-ringing terminal analog front end 20A is as follows.
This is similar to the conventional FIG. When polarity reversal is performed on the transmission lines L1 and L2 from a polarity reversal circuit (not shown) provided in the exchange 10, the polarity reversal detection circuit 40 in the no-ringing terminal analog front end 20 detects this, and its output terminal The detection result is output to 44. This output is the transistor 6 to which the Miller capacitor 65 is added.
Since the base of No. 3 is driven, the loop current required for communication is a polarity reversal circuit (not shown) in the exchange 10 → transmission line L1 → input terminal 31 of the rectifier circuit 30 → positive output terminal 33 of the rectifier circuit 30 → DC loop Current forming resistor 64 → transistor 63 → negative side output terminal 34 of rectifier circuit 30 → input terminal 32 of rectifier circuit 30 → transmission line L2 → switch 10
Flows to the route of the polarity reversing circuit (not shown) while changing smoothly. In the case of a bell signal receiving operation, that is, when a bell signal is sent from the exchange 10 at the time of calling a telephone terminal, the transistor 71 is driven in synchronization with the output of the bell signal detection circuit 50 to generate the bell signal current BI.
Is the bell signal source 16 → ring trip detection resistor 15 →
Current limiting resistor 14 → Switch 13 → Transmission line L2 → Input terminal 32 of rectifier circuit 30 → Positive output terminal 33 of rectifier circuit 30 → Primary winding 61 of transformer 61 in termination circuit 60
a → capacitor 62 (a resistor 64 for forming a DC loop current)
Shunt) → Capacitor 65 → Collector of transistor 71 → Emitter of transistor 71 → Negative output terminal 34 of rectifier circuit 30 → Input terminal 31 of rectifier circuit 30 → Transmission line L1 → Switch 11 in exchange 10 → For current limiting Resistance 12 → battery V _BB → ground.

However, the above proposal also has the following problems. FIG. 5 is a diagram showing the operation waveforms of FIG. 4, and the problems of the no-ringing terminal analog front end of FIG. 4 will be described with reference to FIG. (1) Erroneous trip due to inrush current during reception of bell signal Since each circuit in the no-ringing terminal analog front end 20A always has an operation threshold for operating the circuit, the output current of the bell signal detection circuit 50 ( The transistor 71 driven by (b) of FIG. 5 stops its conduction for a fixed time (t1, t2 in (b) of FIG. 5). However, the output voltage V30 of the rectifier circuit 30 is
Although there is a point where it becomes zero every half cycle, it is continuous as shown in FIG. 5A, and this output voltage V30 is applied to the transistor 63. Further, the output current of the polarity inversion detection circuit 40, that is, the base drive current of the transistor 63 ((c) of FIG. 5) is
It is output continuously. In other words, electrically, the bell signal is a large-amplitude alternating signal that is positive and negative, and therefore appears as a kind of polarity inversion signal. Therefore, the temporary conduction stop of the transistor 71 becomes a temporary conduction of the transistor 63, and several dozen mA to several dozen through the capacitor 62 having a transient impedance lower than that of the DC loop current forming resistor 64 and the primary winding 61a of the transformer. A large transient current of mA will flow. That is, (d) of FIG.
Inrush currents such as J, K, L and M shown in FIG. This transient large current flows from the bell signal source 16 to the ring trip detection resistor 15 to the current limiting resistor 14 to the switch 13.
→ Transmission line L2 → Rectifier circuit 30 → Primary winding 6 of transformer
1a → capacitor 62 (also shunted to current loop forming resistor 64) → transistor 63 → rectifier circuit 30 → transmission line L
1 → Switch 11 → Current limiting resistor 12 → DC power supply V _BB
→ It flows with the ground. As a result, the ring trip detection circuit 17 in the exchange 10 detects the transient large current, and erroneously detects the trip even though it is not a call from the terminal.

(2) False trip due to positive / negative asymmetry of line current at the time of bell reception The output voltage V30 ((a) in FIG. 5) of the rectifier circuit 30 is an AC signal superimposed on the DC power supply V _BB in the exchange 10. It has been rectified. Therefore, the output voltage becomes different every half cycle, and the current value of the current flowing depending on the impedance in the termination circuit 60 changes every half cycle. That is, the current based on the bell signal that flows from the collector to the emitter of the transistor 71 through the Miller capacitor 65 differs every half cycle of the bell signal (see FIG. 5).
(E)), which causes the bell signal current BI flowing through the transmission lines L1 and L2 to be positive and negative asymmetrical as shown in (d) of FIG. The ring trip circuit 17 in the exchange 10 is
A DC component due to the positive / negative asymmetry of the bell signal current BI may be detected, and an erroneous trip may be detected even though the call is not made from the terminal. Particularly, when a plurality of no-ringing terminal analog front ends 20A are multi-connected to the exchange 10, the magnitude of the positive / negative asymmetry of the bell signal current BI increases according to the number of connections. For example, a no-ringing terminal analog front end 20A of 10 terminals
When 10 units are multi-connected to the pair of transmission lines L1 and L2, the magnitude of positive and negative asymmetry becomes 10 times. That is, the risk of detecting an erroneous trip is extremely high, and the line quality is significantly degraded. The present invention solves the problems of the previously proposed technique with respect to detecting an erroneous trip due to an inrush current when a bell signal is received, and detecting an erroneous trip due to an asymmetric bell signal current. It provides a no-ringing terminal analog front end that does.

[0011]

In order to solve the above-mentioned problems, a first invention has first and second input terminals, a positive side output terminal and a negative side output terminal. A rectifier circuit having a second input terminal connected to a pair of transmission lines extending from the exchange; a polarity reversal detection circuit connected to the transmission line for detecting a polarity reversal state on the transmission line; A bell signal detection circuit that is connected in parallel between the side output terminal and the negative side output terminal and that detects a bell signal from the transmission line,
It has a Miller integrator circuit that operates based on the output of the polarity reversal detection circuit to form a DC loop current necessary for no ringing communication, and a termination connected in parallel between the positive side output terminal and the negative side output terminal of the rectifier circuit. In the no-ringing terminal analog front end including the circuit, the following measures are taken. That is, the no-ringing terminal analog front end delays the output of the polarity inversion detection circuit and transfers it to the Miller integrator circuit,
There is provided switching means connected between the delay circuit and the Miller integrating circuit and operated by a drive signal to turn off the Miller integrating circuit. Further, the no-ringing terminal analog front end operates based on the voltage between the positive side output terminal and the negative side output terminal, converts the output level of the bell signal detection circuit, and outputs the detection result of the polarity inversion detection circuit. A control signal generation circuit that generates a reset signal for resetting and a drive signal that is given to the switch means, and a charge storage circuit that smoothes the reset signal and supplies the smoothed reset signal to the reset terminal of the polarity inversion detection circuit are provided.

According to the second invention, the first and second input terminals, the positive side output terminal and the negative side output terminal are provided, and the first and second input terminals are provided.
A rectifier circuit having a second input terminal connected to a pair of transmission lines extending from the exchange; and a polarity reversal detection circuit connected to the transmission line and detecting a polarity reversal state on the transmission line,
A bell signal detection circuit that is connected in parallel between the positive side output terminal and the negative side output terminal of the rectifier circuit and that detects a bell signal from the transmission line, and operates based on the output of the polarity inversion detection circuit to perform no ringing communication. Having a Miller integrating circuit that forms a necessary DC loop current, a terminating circuit connected in parallel between the positive side output terminal and the negative side output terminal of the rectifier circuit,
The following measures are taken in the equipped analog front end of the no-ringing terminal. That is, the Miller integrating circuit has a control electrode, a first electrode, and a second electrode, and the first and second electrodes are made conductive based on the output of the polarity inversion detection circuit given to the control electrode. A switch element that forms the DC loop current, a mirror capacitor that is connected between the first electrode and the control electrode via a rectifying element, and a resistor that sets a potential with respect to the electrode of the mirror capacitor. Is prepared. According to the third invention,
The switch element in the second invention is a transistor in which a first electrode is a collector, a second electrode is an emitter, and a control electrode is a base, and a stabilizing resistor is connected between the base and the emitter. It consists of. Also,
The rectifying element is composed of a diode whose anode is connected to the base, and a high resistance is connected between the cathode of the diode and the emitter of the transistor.

[0013]

According to the first aspect of the invention, since the no-ringing terminal analog front end is configured as described above, the control signal generation circuit generates the reset signal and the drive signal when the bell signal is received. The reset signal is smoothed by the charge storage circuit and transmitted to the polarity inversion detection circuit. For example, when the polarity reversal detection circuit operates to generate an output current when the bell signal is received, the reset signal resets the output of the polarity reversal detection circuit. On the other hand, the output current generated by the operation of the polarity reversal detection circuit at the start of receiving the bell signal is
The signal is delayed via the delay circuit and transmitted to the Miller integrating circuit. Prior to that, the drive signal from the control signal generation circuit operates the switch means to turn off the Miller integrator circuit. According to the second invention, the switching element is
When the switching element is turned on and off based on the output of the polarity reversal detection circuit and the switching element is in the on state, the first and second electrodes are turned on to form a DC loop current required for the noringin communication. When the switching element is off, the mirror capacitor and the resistor bypass between the first and second electrodes of the switching element. For example, if the resistance value of this resistor is increased, the current flowing between the positive side output terminal and the negative side output terminal of the rectifier circuit when the bell signal is received is reduced. According to the third invention, the switching element in the second invention is
The first electrode is formed of a collector, the second electrode is formed of an emitter, and the control electrode is formed of a base, and a stabilizing resistor is connected between the base and the emitter of the transistor. The rectifying element is composed of a diode whose anode is connected to the base, and a high resistance is connected between the cathode of the diode and the emitter of the transistor. Therefore, the above problem can be solved.

[0014]

1 is a circuit diagram of an analog front end of a no-ringing terminal according to an embodiment of the present invention, and FIG.
Alternatively, common reference numerals are given to elements common to the elements in FIG. 4 of the above proposal. This no-ringing terminal analog front end 20B is provided in the exchange 10 having the same configuration as that of the conventional FIG. 2 or the previously proposed FIG.
Connected through. The exchange 10 has a transmission line L
1 has a switch 11 connected to
A battery V _{BB of,} for example, −48V is connected to the battery via a current limiting resistor 12. Further, a switch 13 is connected to the transmission line L2, and a bell signal source 16 of, for example, 16 Hz and 75 Vr.ms is connected to the switch 13 via a current limiting resistor 14 and a ring trip detecting resistor 15. . A ring trip circuit 17 is connected in parallel to the ring trip detection resistor 15. Exchange 10
Although not shown in the figure, other circuits such as a polarity reversing circuit are also provided. The no-ringing terminal analog front end 20B includes a rectifier circuit 30 and a polarity inversion detection circuit 40 that detects and holds the polarity inversion state on the transmission lines L1 and L2.
B and a bell signal detection circuit 50 for detecting a bell signal from the exchange 10 are provided. The rectifier circuit 30 and the bell signal detection circuit 50 have the same configurations as those in FIGS. 2 and 4, and the polarity inversion detection circuit has a reset signal input terminal 45, which is different from FIGS. 2 and 4. 2 and 4, the no-ringing terminal analog front end 20B operates based on the output of the bell signal detection circuit 50 to generate a control signal, and a control signal generation circuit 80.
The termination circuit 100 is provided. The first and second input terminals 31 and 32 of the rectifier circuit 30 and the polarity reversal detection circuit 4
The input terminals 41 and 42 of OB are the pair of transmission lines L1 and L.
Connected to 2. The polarity inversion detection circuit 40B has a holding circuit 43 that holds the detection result. Rectifier circuit 3
0 between the positive-side output terminal 33 and the negative-side output terminal 34 are respectively connected in parallel, and the input terminals 51,
52, the input terminal of the control signal generation circuit 80, and the input terminal of the termination circuit 100 are connected.

The control signal generation circuit 80 includes a transistor 8 whose base is connected to the output terminal 53 of the bell signal detection circuit.
1 and the emitter resistance 82 of the transistor 81, two diodes 83 ₁ and 83 ₂ forming a constant current circuit together with the emitter resistance 82, and stable operation connected between the base and the emitter of the transistor 81. And a zener diode 85 whose anode is connected to the collector of the transistor 81 and which sets the operation start threshold of the control signal generation circuit 80. Control signal generation circuit 80
Further includes two transistors 8 for generating control signals.
6, 87, the emitter resistances 88 and 89 of the transistors 86 and 87, and the emitter resistances 88 and 89,
Two diodes 90 ₁ and 90 _{2 in} series, which form a constant current circuit together with 89, and an operation stabilizing resistor 91 of each of the transistors 86 and 87 are provided. Each transistor 8
The emitters of the transistors 6, 87 are connected to the positive output terminal 33 of the rectifier circuit 30 via the resistors 88, 89, respectively, and the emitter of the transistor 81 is connected to the negative output terminal 34 via the resistor 82. . The bases of the transistors 86 and 87 are connected to the cathode of the Zener diode 85, and the collectors of the transistors 86 and 87 are connected to the first and second output terminals 92 and 93 for outputting control signals, respectively. ing.

The terminating circuit 100 has a primary winding 101a of a transformer 101 for transmitting an AC signal and a secondary winding 101 of the transformer 101, as in FIG. 2 of the related art and FIG. 4 of the above proposal.
b, a capacitor 102 for blocking a direct current in series with the primary winding 101a, and a DC loop current forming resistor 10 in parallel with the primary winding 101a and the capacitor 102.
3 and the secondary winding 101b of the transformer 101 has
Output terminals 104 and 105 for AC signals are connected, and transmission / reception is performed with a modem or the like connected to the outside via the output terminals 104 and 105. Further, the DC loop current forming resistor 103 has a resistance value of several KΩ to several tens KΩ. The termination circuit 100 further includes a high impedance type Miller integrating circuit 110, which is different from the conventional FIG. 2 and the previously proposed FIG. In the high impedance type Miller integrating circuit 110, the collector has the primary winding 10
The rectifier circuit 30 has an emitter for the 1a and the capacitor 102.
Of the transistor 111 which is connected to the negative output terminal 34 of the transistor 111 and operates based on the output of the polarity reversal detection circuit 40B input to the base to form a DC loop current necessary for no ringing communication.
The operation stabilizing resistor 112 connected between the emitters, the Miller capacitor 113 added between the base and collector of the transistor 111, and the cathode of the transistor 1
Rectifier diode 114 connected to the base of 11 and having its anode connected in series with Miller capacitor 113
And a high resistance 115 that is connected to the negative output terminal 34 of the rectifier circuit 30 and sets a potential to one electrode of the mirror capacitor 113.

The first output terminal 92 of the control signal generation circuit
Is the polarity reversal detection circuit 40 via the charge storage circuit 120.
It is connected to the reset signal input terminal 45 of B. The charge storage circuit 120 is connected between the charge storage capacitor 121 connected between the negative output terminal 34 of the rectifier circuit 30 and the first output terminal 92, and the first output terminal 92 and the reset signal input terminal 45. Has a resistor 122. The output terminal 44 of the polarity inversion detection circuit is connected to the base of the transistor 11 in the Miller integrating circuit 110 via the delay circuit 130 and the switching means 140, and the delay circuit 13 thereof is connected.
0 has a capacitor 131 and a resistor 132.
The switch means 140 serves as an input clamp circuit of the Miller integrating circuit 110, and has a transistor 141 having a collector and an emitter connected between the base and the emitter of the transistor 111 in the Miller integrating circuit 110. An operation stabilizing resistor 142 is added between the base and emitter of the transistor 141, and a drive signal is input to the base from the second output terminal 93 of the control signal generation circuit 80, so that the transistor 141 operates.

Next, the operation of the no-ringing terminal analog front end shown in FIG. 1 will be described. FIG. 6 is a diagram showing the operation waveforms of FIG. 1, and the operation of FIG. 1 will be described with reference to FIG. When setting a normal no-ringing communication state, it is similar to the conventional or previous proposal. That is, exchange 1
When polarity inversion is performed on the transmission lines L1 and L2 from a polarity inversion circuit (not shown) provided in 0, the polarity inversion detection circuit 40B in the no-ringing terminal analog front end 20B detects this, and its output terminal 44 The detection result is output to. Since this output drives the base of the transistor 111 to which the mirror capacitor 113 is added, the loop current required for communication causes a polarity reversal circuit (not shown) in the exchange 10 → transmission line L1 → input terminal 31 of the rectifier circuit 30 → Positive side output terminal 33 of rectifier circuit 30 → DC loop current forming resistor 103 → transistor 111 → negative side output terminal 34 of rectifier circuit 30 → input terminal 32 of rectifier circuit 30 → transmission line L2 → not shown in exchange 10 The current flows in the route of the polarity inversion circuit while smoothly changing due to the so-called Miller effect of the mirror capacitor 113.
As described above, the communication state of the no-ringing terminal analog front end 20B is set.

Next, when the telephone terminal is called, the exchange 1
The operation when the bell signal is transmitted from 0 will be described. The output voltage V30 of the rectifier circuit 30 is the DC power supply V _BB (e.g., -48V) of the exchange 10 to which the bell signal (e.g., 75Vr.ms) of the bell signal source 16 is superposed, so that the output voltage V30 of FIG. As shown in (a) of the above, about 15 of | -48V-2 (75) ^1/2 V |
4V and | -48V + 2 (75) ^1/2 V | of about 58V. The bell signal from the exchange 10 is P in FIG.
When the signal is transmitted from the point, the bell signal detection circuit 50 operates and the output current of FIG. 6B is obtained. At this time, P
When the voltage at the point is large, the output voltage V30 exceeds the operation threshold value of the polarity inversion detection circuit 40B, so that the polarity inversion detection circuit 40B also operates ((e) in FIG. 6). The output of the polarity inversion detection circuit 40B is as shown in (f) of FIG.
It is delayed by the delay circuit 130 and supplied to the base of the transistor 111. On the other hand, the control signal generation circuit 80 becomes operable by the output current of the bell signal detection circuit 50. Then, when the output voltage V30 of the rectifier circuit 30 exceeds the threshold value, the Zener diode 85 in the control signal generation circuit 80 becomes conductive, and the transistors 86 and 87 operate to operate 2
Two control signals are generated. These control signals are signals that make the inoperative range (t1, t2 in (b), (c) and (g) of FIG. 6) when the output voltage V30 is less than or equal to the threshold value. One of the two control signals is a reset signal for the polarity inversion detection circuit 40B, and the other is a drive signal for the switch means 140. The reset signal is
After being smoothed through the charge storage circuit 120 as shown in FIG. 6D, it is continuously supplied to the reset signal input terminal 45 of the polarity inversion detection circuit 40B. Therefore, the detection result held in the holding circuit 43 in the polarity inversion detection circuit 40B is reset as shown in (e) of FIG. Since the output of the polarity inversion detection circuit is turned off, the output current of the delay circuit 130, that is, the input current of the Miller integrating circuit 110 stops after the time t3 shown in (f) of FIG.

On the other hand, the drive signal output from the second output terminal 93 of the control signal generating circuit 80 is synchronized with the bell signal, and is represented by t4 in FIG.
Is supplied to. Here, by appropriately selecting the capacitor 131 of several μF and the resistor 132 of several kΩ in the delay circuit 130, and the capacitor 121 of several μF and the resistor 122 of several tens kΩ in the charge storage circuit 120, the time t3.
It may be <t4. As a result, the switch means 1
Reference numeral 40 serves as an input clamp circuit of the Miller integrating circuit 110 that reliably controls the operation of the Miller integrating circuit 110. That is, the inrush current J in the problem of the previous proposal of FIG.
To prevent the occurrence of. Furthermore, after (f) in FIG.
The polarity inversion detection circuit 40B is reset, and the polarity inversion detection circuit 40B does not send the output current. Therefore, even when the switch means 140 for the Miller integrating circuit 110 is in the off state for the time t2 shown in (g) of FIG. 6, the off state of the transistor 111 is maintained. That is, it is possible to prevent the generation of the inrush currents K, L, and M in FIG. The above-described operation is performed, and the bell signal current BI is generated by bell signal source 16 → ring trip detection resistor 15 → current limiting resistor 14 → switch 13 → transmission line L2 → input terminal 32 of rectifier circuit 30 → rectifier circuit 30. Three
Positive output terminal 33 of 0 → transformer 1 in termination circuit 100
01 primary winding 101a → capacitor 102 (also shunted to resistor 103 for forming a DC loop current) → mirror capacitor 113 → resistor 115 → negative side output terminal 3 of rectifier circuit 30
4 → Input terminal 31 of rectifier circuit 30 → Transmission line L1 → Switch 11 in switch 10 → Current limiting resistor 12 → Battery V
_BB → flows to earth. In the bell signal receiving state, the bell signal current BI passing through the mirror capacitor 113 is
The diode 114 blocks the flow into the switch means 140, and its bell signal current BI has a resistance 1 for applying a potential to the electrode of the mirror capacitor 113.
It flows to the negative side output terminal 34 of the rectifier circuit 30 via 15. If the resistance value of the resistor 115 is set to a high resistance, the bell signal current BI passing through the mirror capacitor 113 can reduce the influence on the magnitude of the output voltage V30 of the rectifier circuit 30. Now, assuming that the bell signal frequency f = 16 Hz and the capacitance C of the mirror capacitor 113 is 0.1 μF in the conventional example of FIG. 2, the impedance Z of the mirror capacitor is about 99.5 KΩ, and for example, the output voltage V30 of 154 V is 154 V. 154V when voltage is applied
It is about 1.55 mA determined by /99.5 KΩ. Also,
When 58 V is applied, a bell signal current BI of about 0.58 mA determined by 58 V / 99.5 KΩ flows. The magnitude of the asymmetrical current of the bell signal current BI is 1.55 m
A-0.58 mA = 0.97 mA.

FIG. 7 is a diagram showing a multi-connected no-ringing terminal analog front end. In FIG. 7, for the pair of transmission lines L1 and L2, a plurality of no-ringing terminal analog front ends 20B ₁ to
20B _n are connected. For example, when 10 units are multi-connected, the magnitude of the asymmetric current of the bell signal current BI is 0.97 mA × 10 units = 9.7 mA. Considering overshoot, undershoot, etc. due to the transient response of the terminal or the exchange 10, for example, the exchange 10
There is almost no margin for the minimum ring trip threshold of 12 mA, and the risk of false trips is high. here,
When the resistance value of the resistor 115 is set to about 1 MΩ, the sum of the impedance Z of the mirror capacitor 113 and the resistance value of the resistor 115 is 1.995 MΩ. Therefore, the bell signal current BI is the output voltage V of the applied rectifier circuit 30.
When 30 is 154V, about 154V / 1.995MΩ about 0.0
77mA ... (I) 58V, 58V / 1.995MΩ about 0.02
It becomes 9mA ... (II). Therefore, the magnitude of the positive / negative asymmetric current flowing through the transmission line is 0.077 mA-0.029 mA = 0.00.
It is extremely small at 48 mA and can be regarded as almost symmetrical ((i) and (h) in FIG. 6). That is, as shown in FIG.
Even when 0 units are multi-connected, the positive / negative asymmetric current is
0.048 mA x 10 units = 0.48 mA, and even if the overshoot and undershoot due to the transient response of the terminal or the exchange 10 are taken into consideration, a sufficient margin can be obtained for the minimum ring trip threshold 12 mA in the exchange 10. You can

As described above, in this embodiment, when the bell signal is received, the output of the polarity inversion detection circuit 40B is the delay circuit 13.
0, while the control signal generation circuit 80 operates,
The switch means 140 is driven. Therefore, the bell signal current BI flows while the transistor 111 in the Miller integrating circuit 110 is maintained in the off state. Further, the control signal generation circuit 80 supplies the smoothed reset signal to the polarity inversion detection circuit 40B, and the polarity inversion detection circuit 40B.
The output of B is stopped. These prevent inrush current from being generated when the bell signal is received. In addition, when the bell signal is received, the current flowing through the mirror capacitor 113 is set to the high resistance 1
Since it is flowing to the negative side output terminal of the rectifier circuit 30 via 15, the positive / negative asymmetric current is made small. Therefore, it is possible to prevent an erroneous trip due to positive / negative asymmetry. Especially, the Norling Gink terminal analog front end,
Even when multiple connections are made, the positive / negative asymmetric current does not become large, so that an erroneous trip can be prevented. Furthermore, the control signal generation circuit 80, the Miller integration circuit 110, the charge storage circuit 120, the delay circuit 130, and the switch means 140 can be configured by elements that can be integrated except for a large-capacity capacitor. The end can be miniaturized. The present invention is not limited to the above-mentioned embodiment, and for example, the transistor 1
The transistor 41 or the transistor 111 can be modified in various ways, such as by using other switching means such as a MOS transistor, or by making the termination circuit 100 into another circuit configuration.

[0023]

As described above in detail, according to the first aspect of the invention, the delay circuit for delaying the output of the polarity inversion detection circuit at the time of receiving the bell signal and the switch means at the time of receiving the bell signal are driven to perform the Miller integration. And a charge storage circuit for smoothing a reset signal from the control signal generation circuit and supplying the smoothed reset signal to the polarity inversion detection circuit. Therefore, it is possible to prevent the occurrence of the inrush current at the time of receiving the bell signal and the erroneous trip caused thereby. Second
According to the invention, a rectifying element for blocking a current flowing into the control electrode of the switch element through the mirror capacitor at the time of receiving the bell signal, and a resistor for setting a potential with respect to the electrode connected to the rectifying element of the mirror capacitor. have. By setting the resistance value of the resistor to be large, the current flowing through the mirror capacitor is reduced, and the influence of the asymmetry of the bell signal current is reduced. Therefore, for example, when the no-ringing terminal analog front end is multi-connected, an erroneous trip due to the asymmetry of the bell signal current can be prevented. According to a third aspect of the present invention, the switching element of the second aspect has a structure in which the first electrode is formed of a collector, the second electrode is formed of an emitter, and the control electrode is formed of a base. Since the rectifying element is composed of a diode whose anode is connected to the base and the high resistance is connected between the cathode of the diode and the emitter of the transistor, The device of the second invention can be realized with a simple structure.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a no-ringing terminal analog front end according to an embodiment of the present invention.

FIG. 2 is a circuit diagram showing a conventional no-ringing terminal analog front end.

FIG. 3 is a diagram showing operation waveforms in FIG.

FIG. 4 is a circuit diagram showing a previously proposed no-ringing terminal analog front end.

5 is a diagram showing operation waveforms in FIG. 4;

FIG. 6 is a diagram showing operation waveforms in FIG. 1.

FIG. 7 is a configuration block diagram showing a multi-connected no-ringing terminal analog front end.

[Explanation of symbols]

10 Switch 20, 20A, 20B No-ringing terminal Analog front end 30 Rectifier circuit 31, 32 First and second input terminals 33 Positive side output terminal 34 Negative side output terminal 40, 40B Polarity inversion detection circuit 45 Reset signal input terminal 50 bell Signal detection circuit 60,100 Termination circuit 65,113 Mirror capacitor 80 Control signal generation circuit 110 Mirror integration circuit 111 Switch element 120 Charge storage circuit 130 Delay circuit 140 Switch means L1, L2 Transmission line

Claims (3)

[Claims] 1. A first input terminal, a second input terminal, a positive output terminal,
And a rectifier circuit having negative side output terminals, the first and second input terminals being connected to a pair of transmission lines extending from the exchange, and a polarity inversion state on the transmission lines connected to the transmission line. A polarity reversal detection circuit for detecting, a bell signal detection circuit that is connected in parallel between the positive side output terminal and the negative side output terminal of the rectifier circuit, and detects a bell signal from the transmission line; and an output of the polarity reversal detection circuit. And a termination circuit connected in parallel between the positive side output terminal and the negative side output terminal of the rectifier circuit, which has a Miller integrator circuit that forms a DC loop current required for no ringing communication. In the terminal analog front end, a delay circuit for delaying the output of the polarity reversal detection circuit and transmitting it to the Miller integrator circuit, and a delay circuit connected between the delay circuit and the Miller integrator circuit for driving. Switch means for turning off the Miller integrator circuit in an off state, and operating based on a voltage between the positive side output terminal and the negative side output terminal, converting the output level of the bell signal detection circuit A control signal generation circuit that generates a reset signal that resets the detection result of the polarity inversion detection circuit and a drive signal that is given to the switch means, and a charge storage that smoothes the reset signal and supplies the reset terminal of the polarity inversion detection circuit. A no-ringing terminal analog front end that is equipped with a circuit. 2. A first and a second input terminal, a positive side output terminal,
And a rectifier circuit having negative side output terminals, the first and second input terminals being connected to a pair of transmission lines extending from the exchange, and a polarity inversion state on the transmission lines connected to the transmission line. A polarity reversal detection circuit for detecting, a bell signal detection circuit that is connected in parallel between the positive side output terminal and the negative side output terminal of the rectifier circuit, and detects a bell signal from the transmission line; and an output of the polarity reversal detection circuit. And a termination circuit connected in parallel between the positive side output terminal and the negative side output terminal of the rectifier circuit, which has a Miller integrator circuit that forms a DC loop current required for no ringing communication. In the terminal analog front end, the Miller integrating circuit includes a control electrode, a first electrode and a second electrode.
A switch element that has a second electrode and forms the DC loop current by conducting the first and second electrodes based on the output of the polarity reversal detection circuit given to the control electrode; A no-ringing terminal analog front end, comprising: a mirror capacitor connected between the control electrodes via a rectifying element; and a resistor for setting a potential with respect to the electrodes of the mirror capacitor. 3. The switch element, wherein the first electrode is formed of a collector, the second electrode is formed of an emitter, and the control electrode is formed of a base, and a stabilizing resistor is connected between the base and the emitter. 3. The rectifying element is composed of a diode whose anode is connected to the base, and a high resistance is connected between the cathode of the diode and the emitter of the transistor.
Analog front end with no ringing terminal as described.