JPH07221873A - Terminal equipment system - Google Patents

Abstract

PURPOSE:To provide a slow polarity inversion detection system by which a limit of number of terminal equipments connected in parallel with one line is relieved in the terminal equipment system utilizing no-ringing communication. CONSTITUTION:A rectifier circuit 2 is connected to a telephone line 15, a charging circuit 3 is provided to a secondary side of the rectifier circuit 2, that is charged up in the usual standby state. Since the polarity of the telephone line 15 is inverted slowly, since a voltage of a line L1 or L2 exceeds a prescribed voltage with respect to a negative terminal of the secondary side of the rectifier circuit 2, a voltage detection circuit 5 or 4 detects it to activate a switch circuit 7 or 6 thereby supplying the charge stored in the charging circuit 3 to a photocoupler 8, then the DC resistor of the telephone line 15 is kept high at the detection of the slow polarity inversion signal to relieve the limit in number of terminal equipments connected in parallel with one line.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a terminal device system for calling a terminal device having a polarity reversal detection circuit for performing data communication and remote control using no ringing communication.

[0002]

2. Description of the Related Art A conventional terminal device system includes, for example, a Zener diode, a resistor, a capacitor, and a photocoupler as shown in FIG. 4 as an inexpensive means for detecting the polarity reversal of a telephone line while maintaining circuit insulation. A circuit to which the used bell detection circuit is applied can be considered.

However, if this bell circuit is diverted, no ringing trunk (hereinafter referred to as NRT) is used.
It is difficult to detect a slow-polarity inversion signal when an incoming call arrives at the terminal device when using.

This is because the slow polarity reversal signal gently changes polarity so as not to ring the telephone bell.

As a publicly known example of the technique for detecting the slow polarity inversion signal having such a characteristic, Japanese Patent Laid-Open No. 2-278957 is known.

[0006]

In a circuit to which a bell circuit is applied, a photocoupler is used to transmit a detection signal while insulating a telephone line and a circuit other than the telephone line, and a light emitting diode of the photocoupler is used. The electric current to light up is obtained from the telephone line.

Therefore, when a plurality of terminal devices are connected to one telephone line and a specific one of the terminal devices is selected and called out, a no-ringing communication service of the multiple call system is used in parallel. When the number of connected terminal devices increases, the current for lighting the light emitting diode of the photocoupler increases, so in order to satisfy the technical conditions for connection of the no-ringing communication terminal, which will be described later, the parallel connection is required. It was necessary to limit the number of connectable terminal devices.

The technical condition of connection of a no-ringing communication terminal or the like is that the DC resistance of the DC circuit at the time of receiving a no-ringing ringing signal of a meter terminal or the like and at the time of no-ringing communication is a case where a plurality of meter terminals or the like are connected. However, there was a problem that the value measured with a current of 5 mA or more and 20 mA or less had to be 4 KΩ or more.

[0009]

In a terminal device system for calling a terminal device having a polarity reversal detection circuit from a centralized monitoring center without ringing a telephone connected to the telephone line via a no ringing trunk, the polarity of the telephone line is Connected to the secondary side of the rectifier circuit for accumulating electric charge, the negative side of the secondary side of the rectifier circuit, and one of the telephone lines of the telephone line. , A voltage detection circuit that outputs a signal when the voltage between the connection points becomes a predetermined value or more, and a negative pole side of the secondary side of the rectifier circuit and the other office line of the telephone line, A voltage detection circuit that outputs a signal when the voltage between the connection points becomes a predetermined value or more, and the voltage detection circuit that is connected to the charging circuit and the anode of the diode of the photocoupler. A switch circuit for supplying the charge stored in the charging circuit by an output signal to the photocoupler,
A switch circuit connected to the charging circuit and the anode of the diode of the photocoupler to supply the charge stored in the charging circuit to the photocoupler according to the output signal of the voltage detection circuit, and the switching circuit and the switching circuit have a diode anode. The polarity reversal detection circuit is composed of a photocoupler in which the cathode of the diode is connected to the negative side of the secondary side of the rectifier circuit, and the phototransistor side is connected to the control circuit.

[0010]

[Function] Connect the rectifier circuit to the telephone line to
The electric charge is stored in the capacitor through the telephone line through the high resistance limiting resistor on the next side, and the light emitting diode of the photocoupler is caused to emit light by using this electric charge.

The telephone line on the primary side of the rectifier circuit is judged to have become equal to or higher than a preset voltage value with respect to the negative polarity side of the secondary side of the rectifier circuit. It detects that the polarity has been inverted, and outputs a polarity inversion detection signal.

A switch circuit such as a transistor is operated by the polarity inversion detection signal, and the charge accumulated in the capacitor is supplied to the photocoupler to cause the light emitting diode to emit light.

As described above, by operating the photocoupler by utilizing the electric charge once stored in the capacitor, the polarity reversal signal can be transmitted while maintaining insulation from the telephone line without directly taking the line current from the telephone line. It is possible to increase the DC resistance to the telephone line when the polarity inversion is detected.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing a configuration of a terminal device system showing an embodiment of the present invention, FIG. 2 is a circuit configuration diagram thereof, and FIG. 3 is an operation waveform diagram showing the operation of the circuit.

First, an embodiment of a system using the present invention will be described with reference to FIG.

A centralized monitoring center 11 is housed in the center side exchange 12.

Reference numeral 13 is a terminal side exchange, and a telephone line 15
Are housed.

Reference numeral 16 denotes a telephone, which is connected to the terminal side exchange 13 via a telephone line 15. Reference numeral 17 denotes a terminal device, which is connected to the telephone line 15 in parallel with the telephone 16.

14 is a no ringing trunk (NRT)
Is a switch that is connected to the terminal-side switch 13 and performs no ringing communication, and calls the terminal device 17 without ringing the bell of the telephone 16 by a dial from the centralized monitoring center 11 and calls the centralized monitoring center 1
1 and the communication line of the terminal device 17 are connected.

A polarity reversing circuit 1 constitutes a part of the terminal device 17, and is connected to the telephone line 15 and the control circuit 9.

Reference numeral 9 denotes a control circuit, which is the polarity inverting circuit 1
Is connected to the communication circuit 10 and controls the operation of the terminal device 17.

A communication circuit 10 is connected to the control circuit 9 and the telephone line 15, and is connected to the centralized monitoring center 11
It is a circuit that performs data communication with.

Next, the configuration of a circuit which is an embodiment of the present invention will be described with reference to FIG.

A rectifier circuit 2 is connected to the respective polarities L1 and L2 of the telephone line 15 and supplies a constant polarity to the secondary side of the same rectifier circuit 2 even if the polarities of L1 and L2 are reversed. In this embodiment, a diode bridge circuit is used.

The resistor R1, the resistor R6, the capacitor C1 and the capacitor C2 are components of the charging circuit 3. The resistor R1, the capacitor C1 and the resistor R6 and the capacitor C2 are connected in series, and the other ends of the resistors R1 and R6 are connected. Is a capacitor C on the positive side of the rectifier circuit 2 (hereinafter referred to as point A).
The other ends of 1 and C2 are connected to the negative pole side, and the capacitors C1 and C2 are constantly charged to the power supply voltage of the telephone line 15 via resistors R1 and R6.

The resistor R2, the zener diode ZD1, the resistor R3, and the transistor TR2 are components constituting the voltage detection circuit 4, and the emitter of the TR2, which is an NPN transistor, is on the negative pole side of the rectifier circuit 2 (hereinafter referred to as point B). The base is connected to the point B via the resistor R3, and the base is also connected to the anode of the Zener diode ZD1.

The cathode of the Zener diode ZD1 is connected to L2 of the telephone line 15 via a resistor R2. In this embodiment, the resistor R2 is connected to L2, but the resistor R2 may be connected to either L1 or L2.

The resistor R7, the Zener diode ZD2, the resistor R8, and the transistor TR4 are components of the voltage detection circuit 5. The emitter of the transistor TR4, which is an NPN transistor, is at the point B, and the base is at the point B via the resistor R8. In addition to being connected, the base is Zener diode Z
It is also connected to the anode of D2.

The cathode of the Zener diode ZD2 is connected to L1 of the telephone line 15 via a resistor R7. In this embodiment, the resistor R7 is connected to L1, but the resistor R7 may be connected to the opposite polarity to the polarity of the resistor R2 connected to the telephone line 15.

TR1 is a component of the switch circuit 6 and is a PNP transistor.

The emitter of the transistor TR1 is connected to the contact point of the resistor R1 and the capacitor C1, and the base of the transistor TR1 is connected to the collector of the transistor TR2. When the transistor TR2 is turned on, the transistor TR1 is turned on.
1 is also turned on.

TR3 is a component of the switch circuit 7 and is a PNP transistor.

The emitter of TR3 is connected to the contacts of R6 and C2, and the base of TR3 is connected to the collector of TR4. When TR4 is turned on, TR3 is also turned on.

Reference numeral 8 is a photocoupler, the anode of the light emitting diode is connected to the collector of the transistor TR1 and the collector of the transistor TR3, and the cathode is connected to the point B via the resistor R5.

The transistor side of the photo coupler is connected to the control circuit 9.

The resistor R4 is connected in parallel with the light emitting diode of the photocoupler 8, and the switch circuit 6 is connected.
Alternatively, it is a shunt resistance for preventing the light emitting diode of the photocoupler 8 from being turned on by a leak current flowing except when the charge accumulated by turning on the TR1 or TR3 of the switch circuit 7 is supplied to the photocoupler 8.

Next, the operation will be described with reference to FIG.

FIG. 3 shows operating voltage waveforms of various parts of the circuit when a slow polarity inversion signal is input to the telephone line 15.

The voltage between L1 and L2 indicates the change in voltage between L1 and L2 of the telephone line 15.

The voltage between the point A and the point B is 2 of the rectifier circuit 2.
It shows the voltage change between the positive and negative poles on the next side.

The voltage between the L1 and B points indicates the voltage change between the L1 of the telephone line 15 and the negative pole on the secondary side of the rectifier circuit 2.

The voltage between the points L2 and B indicates the voltage change between the L2 of the telephone line 15 and the negative pole on the secondary side of the rectifier circuit 2.

The PC input current is T of the switch circuit 6.
The current change when R1 or TR3 of the switch circuit 7 is turned on to supply a current to the light emitting diode of the photocoupler 8 is shown.

The PC output current indicates the change in the output current of the output side phototransistor when the PC input current is supplied.

It is assumed that the time now progresses from left to right.

Operation before a This state corresponds to a normal standby state, where L1 is -48V,
This is a region where L2 has a polarity of 0V.

At this time, the voltage between the points L1 and B is -48V for L1, so the voltage at L1 is the diode 1 of the rectifier circuit 2.
It is lower than the point B by Vf, but is approximately 0V.

Therefore, since the base of TR4 of the voltage detection circuit 5 is connected to about 0 V through ZD2 and R7,
TR4 is OFF, so TR3 of the switch circuit 7 is also OF
It becomes F, and C2 is charged from point A to about 48V via R6.

On the other hand, the voltage between the points L2 and B is 0V for L2.
Therefore, the voltage of L2 is about 48V with respect to the point B.

Therefore, since the base of TR2 of the voltage detection circuit 4 is connected to 48V via ZD1 and R2,
If the zener voltage Vz1 of ZD1 is selected to be a voltage lower than 48V, ZD1 is turned on, so TR2 is also turned on, and thus TR1 of the switch circuit 6 is also turned on, and C1 is always discharged.

At this time, since TR1 is ON, the leak current flows from point A through R1 to R4 and R5.
The resistance value is selected so that the voltage generated at R4 due to this leakage current becomes lower than Vf of the light emitting diode of the photocoupler 8 so that the photocoupler 8 does not operate during normal standby.

Operation from a to b: A gentle polarity inversion signal is input, and the voltage between L1 and L2 is 0V.
It is an area that gradually decreases toward.

During this period, the voltage between the points L1 and B does not change, so the state of the voltage detection circuit 5 does not change, and the switch circuit 7 does not change.
Since TR3 also holds the OFF state, the electric charge stored in C2 is held.

At this time, the voltage between the points A and B also gradually decreases toward 0V, so that the charge of C2 leaks out through R6, but since the time from the start of the slow polarity inversion to the end thereof is several seconds, C2 , R6 is sufficiently short with respect to the time constant, and there is no problem.

On the other hand, the voltage between points L2 and B gradually decreases as the voltage between L1 and L2 decreases, and when this voltage falls below Vz1, ZD1 of the voltage detection circuit 4 turns off, so that TR2 turns off. , TR1 of switch circuit 6 is also OFF
To do.

Operation from b to c Slow polarity inversion is in progress and the voltage between L1 and L2 is temporarily 0.
This is a region that becomes V.

Since the voltage between points L1 and B does not change during this time, the states of the voltage detection circuit 5, the switch circuit 6 and C2 are the same as the operations from a to b.

The voltage between points L2 and B is also 0V,
TR2 of the voltage detection circuit 4 and TR1 of the switch circuit 6 are O
Although FF is performed, the voltage between points A and B is 0 V, so C1
Is not charged.

Operation from c to e Slow polarity reversal progresses further, and from L to L2 from c to e
The polarity is reversed and the voltage gradually increases, and at L1-L
This is a region where the voltage between the two becomes 48V.

At this time, the voltage between points L1-B is L1-
It gradually increases as the voltage across L2 increases. If the zener voltage of ZD2 of the voltage detection circuit 5 is Vz2, ZD2 is turned on and TR4 is turned on when the voltage between points L1 and B gradually increases and reaches Vz2 shown by d in the figure.

Since TR3 of the switch circuit 7 is turned on along with this, the electric charge stored in C2 is transferred to the photocoupler 8.
Is supplied to the control circuit 9, and the light emitting diode emits light while the discharge of C2 continues, and transmits the signal of the slow polarity inversion detection to the control circuit 9.

On the other hand, the voltage between the points L2 and B is 0 V and does not change, and TR2 of the voltage detection circuit 4 and TR1 of the switch circuit 6 are present.
Is off. At this time, the voltage between points A and B is L1-
As the voltage across L2 increases, C1 starts charging via R1.

Operation from e to f This state is a region where the polarity between L1 and L2 is inverted by the gentle polarity inversion and 48V is applied.

This state is L, which is different from the above-mentioned area before a.
Only the polarity between 1 and L2 is reversed.

Therefore, the voltage detection circuit 4 and the switch circuit 6
And C1, the voltage detection circuit 5, the switch circuit 7 and C2
The operation of is switched, but the operation in the standby state similar to the area before a is performed.

Hereinafter, a region from f to g, a region from g to h,
Similarly, even if the region from h to i and the region from i to j are attached, L
Only the polarities between 1 and L2 are reversed, and the voltage detection circuit 4, switch circuit 6 and C1 in the regions a to b, the regions b to c, the regions c to d, and the regions d to e, respectively
Then, the operations of the voltage detection circuit 5, the switch circuit 7 and the C2 are merely interchanged.

As is clear from the above description, in the present invention, L1 and L2 are connected to -48 V and L2 to 0 V, respectively.
The polarity reversal between is detected.

Further, according to the present invention, the polarity inversion signal is not limited to the slow polarity inversion signal, and the normal polarity inversion signal is in the range from a to e.
It can be considered that the region from f to j is very short and is detected similarly to the slow polarity inversion signal.

[0070]

As described above, according to the present invention, when a slow polarity inversion signal is detected, it is necessary to directly obtain from the telephone line the current supplied to the photocoupler for transmitting the detection signal while maintaining insulation from the telephone line. Since it is eliminated, the DC resistance of the DC circuit of the telephone line at the time of signal detection can be increased, and the number of terminal devices that can be connected to one telephone line can be increased, thereby providing a useful terminal device system. .

[Brief description of drawings]

FIG. 1 is a configuration block diagram of a terminal device system showing an embodiment of the present invention.

FIG. 2 is a circuit configuration diagram of a terminal device system showing an embodiment of the present invention.

FIG. 3 is a circuit operation waveform diagram of a terminal device system showing an embodiment of the present invention.

FIG. 4 is a circuit diagram of a general bell detection circuit showing a conventional terminal device system.

[Explanation of symbols]

 1 Polarity Inversion Circuit 2 Rectifier Circuit 3 Charging Circuit 4 Voltage Detection Circuit 5 Voltage Detection Circuit 6 Switch Circuit 7 Switch Circuit 8 Photocoupler 9 Control Circuit 11 Centralized Monitoring Center 14 No Ringing Trunk 15 Telephone Line 16 Telephone 17 Terminal Equipment

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kuniaki Ito 3-3 Shinjuyoji, Kashiwa-shi, Chiba Prefecture 1 Home Tech Co., Ltd. (72) Inventor Junichi Shimizu 3-3 Shinjuyoji, Kashiwa-shi, Chiba Prefecture 1 Hitachi, Ltd. In Home Tech

Claims (1)

[Claims] 1. A terminal device (17) having a polarity reversal detection circuit (1) without ringing a telephone set (16) connected to a telephone line (15) from a centralized monitoring center (11) via a no ringing trunk (14). ), A rectifying circuit (2) for rectifying the polarity of the telephone line (15), and a charging circuit (3) connected to the secondary side of the rectifying circuit (2) for accumulating charges. , The negative side of the secondary side of the rectifier circuit (2) and the telephone line (15)
A voltage detection circuit (4) which is connected to either one of the station lines and outputs a signal when the voltage between the connection points becomes a predetermined value or more, and a minus on the secondary side of the rectification circuit (2). A voltage detection circuit (5) that is connected to the other side of the telephone line (15) on the pole side and outputs a signal when the voltage between the connection points exceeds a predetermined value, and the charging circuit ( A switch circuit (6) which is connected to the anode of the diode of (3) and the photocoupler (8) and supplies the charge accumulated in the charging circuit (3) to the photocoupler (8) by the output signal of the voltage detection circuit (4). ), And the charge accumulated in the charging circuit (3) by the output signal of the voltage detection circuit (5) connected to the anodes of the diode of the charging circuit (3) and the photocoupler (8).
An anode of a diode is connected to the switch circuit (7) supplied to the switch circuit (6) and the switch circuit (6) and the switch circuit (7), and a cathode of the diode is connected to the negative side of the secondary side of the rectifier circuit (2), A terminal device system comprising a polarity reversal detection circuit (1) comprising a photocoupler (8) whose phototransistor side is connected to a control circuit (9).