JPH09205494A - Network controller for on-ringing communication - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a network controller for no-ringing communication capable of using the IC of low breakdown strength and being miniaturized and economized by reducing the voltage applied to an internal circuit. SOLUTION: When a second high breakdown strength switching transistor(TR 3) 9 is turned ON at the time of no-ringing call termination, the voltage from a telephone line 1 is applied through a diode bridge circuit 3, the second high breakdown strength switching transistor(TR3) 9 and a Zener diode(ZD1) 11 to the internal circuit 7 made into the IC. The voltage from the telephone circuit 1 is reduced for the constant voltage of the Zener diode(ZD1) 11 and applied to the internal circuit 7 made into the IC as a relatively small voltage.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a telephone line from a center device to a terminal device of each consumer in an automatic meter reading system or the like for automatically measuring the usage of electricity, gas, water, etc. via a telephone line. The present invention relates to a network control device for no-ringing communication used to receive a no-ringing communication via a telephone line. More specifically, the network control device is connected between a telephone line and a terminal device and responds to a no-ringing call from the telephone line. While transmitting the incoming call to the terminal device,
The present invention relates to a no-ringing communication network control device that performs terminal call communication to a telephone line in response to a call from a terminal device.

[0002]

2. Description of the Related Art This type of network controller for no-ringing communication is provided for each customer when used in an automatic meter reading system, so that its internal circuit can be integrated into an IC to achieve miniaturization and economy. It is necessary, but in no ringing communication, there is a provision that "the DC resistance when the subscriber telephone circuit is" semi-closed "must be 4 kΩ or more when measured at a current value of 5 mA to 20 mA". Therefore, the voltage applied from the telephone line side to the input end of the no-ringing communication network control device is about 43 volts, which is a considerably high voltage, and when the internal circuit of the no-ringing communication network control device is integrated into an IC, the withstand voltage of the IC is reduced. Needs to be quite high.

More specifically, as shown in FIG. 6, when the no-ringing communication network control device 63 is connected to the exchange 61 via the telephone line 62 during no-ringing communication, the exchange 61 has a total protection resistance. A resistance of 440Ω is connected, and the DC voltage of the exchange 61 is 48V via this resistance.
Is further supplied to the network controller 63 for no ringing communication through the telephone line 62. If the DC resistance value of the network controller is set to the above-mentioned minimum value of 4 kΩ as shown in the figure, the network controller Telephone line connection terminal L, which is the input terminal
The voltage Vn applied to 1, L2 is

## EQU00001 ## Vn = 4000.times.48 / (220 + 4000 + 220) .apprxeq.43.2V (1), and a relatively high voltage of about 43V is applied to the no-ringing communication network controller 63.

On the other hand, in the case of performing terminal call communication using a call mode similar to that of an ordinary telephone, the electrical condition is that "DC resistance when the subscriber telephone circuit is closed is 2
It must be 50Ω to 300Ω when measured at a current value of 0 mA to 120 mA. ”Therefore, as shown in FIG. 7, if the DC resistance of the no-ringing communication network controller 63 is set to the minimum of 50Ω, The voltage Vt applied to the telephone line connection terminals L1 and L2 of the network control device is

## EQU00002 ## Vt = 50.times.48 / (220 + 50 + 220) .apprxeq.4.9V (2), and a low voltage of about 5V is applied to the network controller 63. Therefore, generally, in a telephone or the like, an IC having a withstand voltage of about 10V to 15V is used as an IC used similarly to the terminal call communication of the network control device.

[0005]

As described above, when the internal circuit of the no-ringing communication network control device is integrated into an IC, the withstand voltage of the IC is required to be about 50V or more,
The withstand voltage is required to be about 5 times higher than that of the IC used in general telephones, but in the case of IC, the higher the withstand voltage is, the larger the area of the IC chip becomes, even with the same circuit configuration. As a result, there is a problem that the cost of the IC is increased.

It is to be noted that it is highly regulated that the DC resistance value should be 4 kΩ or more at the time of no-ringing communication because the exchange is "detected that the telephone line is off-hook because the line current of 20 mA or more flows. This is because there is a function to do. Therefore, during no-ringing communication, it is necessary to prevent the current more than the off-hook detection current from flowing in any state.

[0007] The present invention has been made in view of the above,
It is an object of the present invention to provide a no-ringing communication network control device which can use an IC having a low withstand voltage by reducing the voltage applied to an internal circuit, and which can achieve miniaturization and economy. .

[0008]

In order to achieve the above object, the present invention according to claim 1 is connected between a telephone line and a terminal device, and responds to a no ringing incoming call from the telephone line from the telephone line. Is a network control device for no-ringing communication, which transmits an incoming call to the terminal device, and responds to a call from the terminal device to perform terminal calling communication on the telephone line,
A diode bridge means connected to the telephone line for aligning the polarity of the voltage from the telephone line in a certain direction, and connected between the diode bridge means and the internal circuit, and the internal circuit is connected to the diode during call communication of the terminal. First high withstand voltage switch means for selectively transmitting to the telephone line through the bridge means and between the diode bridge means and the internal circuit, the telephone line is connected through the diode bridge means when no ringing is received. Second high withstand voltage switch means for connecting to the internal circuit, and the second high withstand voltage switch means connected in series with the second high withstand voltage switch means, and the diode bridge means and the second high withstand voltage switch from the telephone line when no ringing is received. And a constant voltage means for reducing the voltage transmitted to the internal circuit via the means. .

According to the first aspect of the present invention, when the second high breakdown voltage switch means is turned on at the time of no ringing incoming, the voltage from the telephone line is the diode bridge means and the second high breakdown voltage switch. Means, and through the constant voltage means, to the internal circuit, the relatively high voltage from the telephone line is reduced to a small value by the constant voltage means, and a relatively small voltage is applied to the internal circuit, The internal circuit can be composed of an IC having a low breakdown voltage.

The present invention described in claim 2 is the same as the claim 1.
In the invention described above, a series termination circuit comprising a terminating resistor and a capacitor for terminating the telephone line with a predetermined AC impedance when the telephone line is connected to an internal circuit via the second high voltage switch means. And a high resistance connecting means for connecting a high resistance in series when no ringing arrives, and a high resistance disconnecting means for disconnecting the high resistance from the series termination circuit after the charging of the capacitor via the high resistance is completed. And

According to the second aspect of the present invention, at the time of no ringing incoming, a high resistance is connected to a series termination circuit composed of a termination resistance and a capacitor to reduce an inrush charging current to the capacitor, thereby increasing the high resistance. The high resistance is disconnected from the series termination circuit after the charging of the capacitor via the circuit is completed, thereby terminating the telephone line with a predetermined AC impedance.

Further, the present invention according to claim 3 provides the invention according to claim 1.
Alternatively, in the invention described in item 2, it comprises a terminating resistor and a capacitor for terminating the telephone line with a predetermined AC impedance when the telephone line is connected to an internal circuit through the first or second high voltage switch means. The gist of the present invention is to have a correction unit that corrects the difference between the alternating current impedance formed by the series termination circuit when no ringing is received and the alternating current impedance formed during terminal call communication.

According to the third aspect of the present invention, the difference between the AC impedance formed at the time of no ringing incoming call and the AC impedance formed at the terminal calling communication is corrected by the series termination circuit including the termination resistor and the capacitor. Is corrected by.

According to a fourth aspect of the present invention, in the invention according to the third aspect, the correcting means has a correcting resistor connecting means for connecting a correcting resistor in parallel or in series with the terminating resistor.

According to the present invention of claim 4, a correction resistor is connected in parallel or in series with the terminating resistor, and correction is made so that the AC impedance during no ringing communication and the AC impedance during terminal calling communication are matched. ing.

The present invention according to claim 5 provides the invention according to claim 3.
In the invention described above, the gist is that the correcting means separately provides a terminating resistor for no ringing communication and a terminating resistor for terminal calling communication as the terminating resistors.

According to the present invention, the terminating resistor for no ringing communication and the terminating resistor for terminal calling communication are separately provided, and the AC impedance for no ringing communication and the AC for terminal calling communication are provided. Match the impedance.

[0018]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a circuit diagram showing a configuration of a network controller for no-ringing communication according to an embodiment of the present invention. In the network controller for no-ringing communication shown in the figure, a diode bridge circuit 3 is connected to a telephone line 1 via telephone line connecting terminals L1 and L2, and the polarity of the voltage applied from the telephone line 1 by the diode bridge circuit 3 is polarity. Are aligned in a certain direction and output to the internal circuit of the no-ringing communication network controller.

The output of the diode bridge circuit 3 is connected to the IC internal circuit 7 via the first high breakdown voltage switching transistor (TR1) 5 which is turned on at the time of terminal call communication, and is turned on at the time of no ringing incoming call. Second high breakdown voltage switching transistor (TR3) 9
Similarly, it is connected to the IC internal circuit 7 via the Zener diode (ZD1) 11.

The first high withstand voltage switching transistor (TR1) 5 has a first resistor (R) between the emitter and the base.
1) Connected at 13, and the base is about 3-5
It is connected to the collector of the first drive transistor (TR2) 17 via the second resistor (R2) 15 of kΩ, and the third resistor (R3) is provided between the base and the emitter of the transistor.
19 are connected. Furthermore, an off-hook signal (OFF-HOO) is applied to the base of the first drive transistor (TR2) 17.
K) is supplied.

The off-hook signal (OFF-HOOK) is transmitted to the first drive transistor (TR2) 1 at the time of the terminal call communication.
The first drive transistor (TR2) 17 is turned on by being supplied to the base of the transistor 7, thereby causing the collector current of the transistor to flow as the base current of the first high breakdown voltage switching transistor (TR1) 5, The high breakdown voltage switching transistor (TR1) 5 of No. 1 is turned on, and the telephone line 1 is connected to the IC integrated circuit 7 via the diode bridge circuit 3.

In the second high breakdown voltage switching transistor (TR3) 9, the emitter and the base are connected by a fourth resistor (R4) 21 and the base is about 100.
The second drive transistor (TR) is connected through the fifth resistor (R5) 23 having a relatively high resistance value of kΩ (about 100 kΩ).
4) It is connected to the collector of 25, and the sixth resistor (R6) 27 is connected between the base and emitter of the transistor. Further, the second drive transistor (TR4) 25
No-ringing communication ON signal (NR-ON) is supplied to the base of the.

Then, when the no-ringing communication ON signal (NR-ON) is supplied to the base of the second drive transistor (TR4) 25 upon arrival of the no-ringing, the second drive transistor (TR4) 25 is turned on, As a result, the collector current of the transistor flows as the base current of the second high breakdown voltage switching transistor (TR3) 9, the second high breakdown voltage switching transistor (TR3) 9 is turned on, and the diode bridge circuit 3
The telephone line 1 is connected to the IC integrated circuit 7 via the.

The collector which is the output of the first high breakdown voltage switching transistor (TR1) 5 and the IC internal circuit 7
Is connected to one end of a capacitor (C1) 33, and the other end of the capacitor (C1) 33 is connected to a terminating resistor (R7) 2 of 600Ω for determining an AC impedance.
9 and the resistance value of the second resistor (R2) 15 is substantially equal to 60 and at the time of no ringing incoming call.
One end of each correction resistor (R8) 31 for correcting the 0Ω AC impedance is connected.

The other end of the terminating resistor (R7) 29 has a high resistance (R9) 35 having a relatively high resistance value of several kΩ to several tens kΩ for reducing the rush charging current to the capacitor (C1) 33. And a third switching element (SW3)
It is connected to the reference potential via 37 and is also directly connected to the reference potential via the fourth switching element (SW4) 39. The other end of the correction resistor (R8) 31 is connected to the reference potential via the fifth switching element (SW5) 41.

Third switching element (SW3) 37
Is turned on by a Z-ON signal, which will be described later, when there is no ringing incoming, thereby connecting the capacitor (C1) 33 and the terminating resistor (R7) 29 to the reference potential via the high resistor (R9) 35, and thereby the capacitor ( C1) 33
The inrush charge current to is reduced. The fourth switching element (SW4) 39 is turned on by a 600Ω signal described later when the capacitor (C1) 33 is charged after the Z-ON signal and the inrush charging current becomes sufficiently small, which causes the fourth switching element (SW4) 39 to turn on. The telephone line 1 is terminated with 600Ω of the terminating resistor (R7) 29. Further, the fifth switching element (SW5) 41 is turned on by the Z-CONT signal described later after the 600Ω signal, thereby connecting the correction resistor (R8) 31 in parallel to the terminating resistor (R7) 29. , The AC impedance by the terminating resistor (R7) 29 is corrected.

Further, the collector of the first high breakdown voltage switching transistor (TR1) 5 and the capacitor (C1) 33.
The connection point between and is connected to the reception amplifier 45 of the IC internal circuit 7 via the capacitor (C2) 43, whereby the signal from the telephone line 1 is amplified and a reception signal is generated.

The connection point between the first high breakdown voltage switching transistor (TR1) 5 and the capacitor (C1) 33 is further extended to the integrated circuit IC 7, where the first constant current circuit (120 mA) 47 and the first constant current circuit 47 are connected. 1 switching element (S
W1) 51 is connected to the reference potential via a series circuit, and the second constant current circuit (10 mA) 49 is also similarly connected.
And a second switching element (SW2) 53 connected in series to the reference potential. Further, a transmission amplifier 55 is connected in parallel to these via an electromotive force unit, and a transmission signal is sent to the telephone line 1 via the transmission amplifier 55.

First switching element (SW1) 51
Is turned on by an off-hook signal (OFF-HOOK), thereby connecting the first constant current circuit (120 mA) 47 to the telephone line 1 and realizing a DC resistance value of 50Ω to 300Ω during terminal call communication. ing. In addition, the second switching element (SW2) 53 is turned on by the no-ringing communication ON signal (NR-ON), which connects the second constant current circuit (10 mA) 49 to the telephone line 1 for no ringing communication. A DC resistance value of 4 kΩ or more has been realized.

Next, the operation of the no-ringing communication network controller configured as described above will be described with reference to FIG.

First, the operation at the time of no ringing incoming call will be described. When the no-ringing communication ON signal (NR-ON) is turned on at the time of no-ringing incoming call as shown in FIG. 2A, the second drive transistor (TR4) 2
5 is turned on, the second high breakdown voltage switching transistor (TR3) 9 is turned on, and the second ring switching communication signal (NR-ON) turns on the second switching element (SW2) 53. As a result, the telephone line 1 is connected to the IC integrated circuit 7 through the diode bridge circuit 3, the second high breakdown voltage switching transistor (TR3) 9 and the Zener diode (ZD1) 11, and the second switching element ( When the SW2) 53 is turned on, the second constant current circuit (10 mA) 49 is connected to the telephone line 1 through the same path, and realizes a DC resistance of 4 kΩ or more during no ringing communication.

In this way, the telephone line 1 is integrated into the IC internal circuit 7
In the circuit configuration connected to, since the Zener diode (ZD1) 11 is connected in the path, the voltage V _L applied to the integrated circuit IC 7 is as described above (1 The voltage value is obtained by subtracting the constant voltage V _ZD1 of the Zener diode (ZD1) 11 from the voltage 43.2V expressed by the equation).

V _L = 43.2−V _ZD1 (3) By connecting the Zener diode (ZD1) 11 to the second high breakdown voltage switching transistor (TR3) 9 in series in this way, the IC internal circuit 7 is formed. The applied voltage V _L can be set to a considerably low voltage by subtracting the constant voltage of the Zener diode (ZD1) 11, and for example, the constant voltage V _ZD1 of the Zener diode (ZD1) 11 is set to 35.
When it is set to V, the voltage V _L applied to the IC-forming internal circuit 7 can be reduced to 8.2 V, whereby an IC having a low withstand voltage can be used, and downsizing and economy can be achieved. .

As described above, the second high breakdown voltage switching transistor (TR3) 9 is turned on to turn on the telephone line 1.
A diode bridge circuit 3, a second high breakdown voltage switching transistor (TR3) 9, a Zener diode (Z
It is necessary to connect a terminating resistor (R7) 29 through a capacitor (C1) 33 in order to terminate the telephone line 1 with an AC impedance of 600Ω after connecting the IC internal circuit 7 through D1) 11. Yes, but in this case 600
When the Ω terminating resistor (R7) 29 is directly connected, an inrush charging current flows through the capacitor (C1) 33,
This current is detected as an off-hook current by the exchange. Therefore, in order to prevent this, in the present embodiment, first, as shown in FIG. 2B, the third switching element (SW3) 37 is activated by the Z-ON signal. To turn on the high resistance (R9) 3 in series with the terminating resistance (R7) 29.
5 is connected.

By thus connecting the high resistance (R9) 35 in series with the terminating resistance (R7) 29, the inrush charging current Ic flowing through the capacitor (C1) 35 is

## EQU3 ## Ic = _VL / (R7 + R9) where R9 (several kΩ to several tens kΩ) >> R7 (600Ω)
Is reduced to a very small value and is not detected as off-hook current by the exchange.

After charging the capacitor (C1) 33 with such a very small charging current, the fourth switching element (SW4) receives a 600Ω signal as shown in FIG. 2C.
By turning on 39, the terminating resistor (R7) 29 is directly connected without passing through the high resistor (R9) 35, and the telephone line 1 can be terminated with an AC impedance of 600Ω.

As described above, the terminating resistor (R7) 29 is connected to the telephone line 1 by the fourth switching element (SW4) 39, whereby the telephone line 1 is terminated with an AC impedance of 600Ω, and then the In an embodiment,
As shown in FIG. 2D, the fifth switching element (SW5) 41 is turned on by the Z-CONT signal, the correction resistor (R8) 31 is connected in parallel to the termination resistor (R7) 29, and the telephone line 1 is connected. The AC impedance is corrected. The AC impedance in this case is a parallel resistance value of the terminating resistor (R7) 29 and the correction resistor (R8) 31, which is, as will be described below, the terminating resistor (R7) at the time of terminal outgoing call communication. ) 29 and the second resistor (R2) 15 in parallel with each other to match the AC impedance.

That is, in the terminal calling communication, FIG.
As shown in (a), the first switching element (SW1) 51 is turned on by the off-hook signal (OFF-HOOK) to connect the first constant current circuit (120 mA) 47 and the first drive transistor (SW1). TR2) 17 is turned on, whereby the first high breakdown voltage switching transistor (TR1) 5 is turned on, and the IC internal circuit 7 is called via the first high breakdown voltage switching transistor (TR1) 5 and the diode bridge circuit 3. It is connected to the line 1 so that it can make a call, and the first constant current circuit (120 mA) 47 is connected to the telephone line 1 via the first high voltage switching transistor (TR1) 5.
Therefore, in the case of this terminal calling communication, a current of about 120 mA is applied to the first high breakdown voltage switching transistor (TR
1) 5, so that the second resistor (R2) 15 that drives the first high breakdown voltage switching transistor (TR1) 5
Must be reduced to a few kΩ.

As described above, after the first high breakdown voltage switching transistor (TR1) 5 is turned on and the first constant current circuit (120 mA) 47 of the IC internal circuit 7 is connected to the telephone line 1. Also in the terminal call communication, as shown in FIG. 3 (b), the fourth switching element (SW4) 39 is turned on by the 600Ω signal, and the terminating resistor (R7) 29 of 600Ω is connected. Line 1
Is terminated with an AC impedance of 600Ω.

Thus, the terminating resistance (R7) 2 of 600Ω
When the telephone line 1 is terminated at 9, the terminating resistor (R7) 29 is connected in parallel to the second resistor (R2) 1 of several kΩ.
Since 5 is connected, the actual AC impedance to the telephone line 1 is the parallel resistance of the terminating resistor (R7) 29 and the second resistor (R2) 15.

That is, during terminal calling communication, the AC impedance of 600Ω is slightly lower than that during no ringing communication due to the influence of the second resistor (R2) 15.

Therefore, at the time of no ringing communication, the correction resistor (R8) 31 having a resistance value substantially equal to that of the second resistor (R2) 15 is terminated as described above in order to match the AC impedance at the time of this terminal calling communication. Resistance (R
7) It is connected in parallel to 29. As a result, the AC impedance corrected by the correction resistor (R8) 31 in the no ringing communication becomes almost the same as the AC impedance affected by the second resistor (R2) 15 in the terminal call communication.

FIG. 4A is a circuit diagram of a main part according to another embodiment of the present invention.

In the embodiment shown in FIG. 1 described above, 600
In order to match the AC impedance generated by the Ω terminating resistor (R7) 29 between the no ringing communication and the terminal calling communication, the terminating resistor (R7) 29 has a correction resistor (R8).
Although 31 are connected in parallel, in the embodiment shown in FIG.
Compensation resistor (R8) for terminating resistor (R7) 29 of 00Ω
1) 61 is connected in series so that the AC impedances during no ringing communication and terminal calling communication are matched.

That is, as shown in FIG. 4 (b), the fourth switching element (SW
4) By turning on 39, the terminating resistor (R7) 2
While the telephone line 1 is terminated by the AC impedance of 600Ω of 9, the fifth switching element (SW5) 41 is turned on during the terminal call communication, so that the termination resistor (R7) 29 and the correction resistor (R81) are connected. ) 61 is connected in parallel to the second resistor (R2) 15 so that the parallel resistance of both is set to be equal to 600Ω of the terminating resistor (R7) 29 at the time of no ringing communication. The AC impedances during communication and terminal call communication are matched.

FIG. 5A is a circuit diagram of a main part according to another embodiment of the present invention.

The above-described embodiment shown in FIG. 1 and FIG.
In the embodiment shown in (1), by connecting the correction resistors (R8) 31 and (R81) 61 to the terminating resistor (R7) 29 in parallel or in series, the AC impedance at the time of no ringing communication and at the time of terminal calling communication can be improved. Although they are matched with each other, in the embodiment shown in FIG. 5A, the terminating resistors for AC impedance are separately provided for no-ringing communication and for terminal calling communication.

That is, in the embodiment shown in FIG. 5A, the AC impedance for no ringing communication is 6
A terminating resistor (R7) 29 of 00Ω is provided, and the terminating resistor (R7) 29 is connected to the fourth switching element (SW4) 39.
The terminal resistance (R71) 63 having a resistance value of 600Ω + α is used as the AC impedance during terminal call communication.
And the terminating resistor (R71) 63 is connected by the fifth switching element (SW5) 41.

In such a configuration, as shown in FIG. 5 (b), the fourth switching element (SW4) 39 is turned on during no ringing communication and the terminating resistor (R7).
While the telephone line 1 is terminated with an AC impedance of 29 of 600Ω, the fifth switching element (SW5) 41 is turned on at the time of terminal call communication to obtain 600Ω + α.
The terminating resistor (R71) 63 of the second resistor (R2) 1
5 is connected in parallel so that the parallel resistance of both is set to be equal to 600Ω of the terminating resistance (R7) 29 at the time of no ringing communication so that the AC impedances at the time of no ringing communication and the terminal call communication are matched. Is what you are doing.

[0051]

As described above, according to the present invention as set forth in claim 1, when the second high withstand voltage switch means is turned on at the time of no ringing incoming, the voltage from the telephone line is diode bridge means, The relatively high voltage from the telephone line transmitted to the internal circuit via the second high voltage switch means and the constant voltage means is reduced to a small value by the constant voltage means, and the internal circuit has a relatively small voltage value. Is applied, the internal circuit can be composed of an IC having a low withstand voltage, and downsizing and economy can be achieved.

According to the second aspect of the present invention, when no ringing is received, a high resistance is connected to the series termination circuit composed of the termination resistance and the capacitor to reduce the inrush charge current to the capacitor, thereby reducing the high current. After the charging of the capacitor via the resistor is completed, the high resistance is disconnected from the series termination circuit, which terminates the telephone line with a predetermined AC impedance, so the exchange of the charging current to the capacitor may be falsely detected as off-hook. No ringing incoming call can be made accurately.

Further, according to the present invention as set forth in claims 3 to 5, the difference between the AC impedance formed at the time of no ringing incoming call and the AC impedance formed at the terminal call communication by the series termination circuit including the termination resistor and the capacitor. The correction resistor is connected in parallel or in series with the terminating resistor to correct the AC impedance during no ringing communication and the AC impedance during terminal calling communication, or no ringing is performed. The terminal resistance for communication and the terminal resistance for terminal call communication are separately provided so that the AC impedance during no ringing communication and the AC impedance during terminal call communication match.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a configuration of a no-ringing communication network control device according to an embodiment of the present invention.

FIG. 2 is a timing diagram showing an operation of the network controller for no-ringing communication shown in FIG. 1 during no-ringing communication.

FIG. 3 is a timing diagram showing an operation of the no-ringing communication network control device shown in FIG. 1 during terminal calling communication.

FIG. 4 is a circuit diagram of a main part according to another embodiment of the present invention.

FIG. 5 is a circuit diagram of a main part according to another embodiment of the present invention.

FIG. 6 is a diagram showing a circuit state of the network controller for no-ringing communication during no-ringing communication.

FIG. 7 is a diagram showing a circuit state of a no-ringing communication network control device during terminal call communication.

[Explanation of symbols]

 1 Telephone line 3 Diode bridge circuit 5 First high voltage switching transistor (TR1) 7 IC internal circuit 9 Second high voltage switching transistor (TR3) 11 Zener diode (ZD1) 15 Second resistance (R2) 29 Termination Resistance (R7) 31 Correction resistance (R8) 33 Capacitor (C1) 35 High resistance (R9)

Front page continued (72) Inventor Yuichi Hirayama 70 Yanagimachi, Saiwai-ku, Kawasaki-shi, Kanagawa Toshiba Yanagimachi factory

Claims (5)

[Claims] 1. A connection between a telephone line and a terminal device,
It is a network controller for no-ringing communication that transmits an incoming call from a telephone line to a terminal device in response to a no-ringing incoming call from a telephone line, and performs terminal calling communication to a telephone line in response to a call from the terminal device. Connected to the telephone line and connected between the diode bridge means for aligning the polarity of the voltage from the telephone line in a certain direction and the diode bridge means and the internal circuit. First for selectively transmitting to a telephone line through said diode bridge means
A high withstand voltage switch means, and a second high withstand voltage switch means connected between the diode bridge means and the internal circuit for connecting a telephone line to the internal circuit via the diode bridge means when no ringing is received. It is connected in series to the second high withstand voltage switch means, and is a constant voltage for reducing the voltage transmitted from the telephone line to the internal circuit through the diode bridge means and the second high withstand voltage switch means at the time of no ringing incoming call. A network control device for no-ringing communication, comprising: a voltage means. 2. A series termination circuit comprising a terminating resistor and a capacitor for terminating the telephone line with a predetermined AC impedance when the telephone line is connected to an internal circuit through the second high voltage switch means. High resistance connecting means for connecting a high resistance in series when no ringing arrives, and high resistance disconnecting means for disconnecting the high resistance from the series termination circuit after the charging of the capacitor via the high resistance is completed. The network controller for no-ringing communication according to claim 1. 3. A series termination composed of a terminating resistor and a capacitor for terminating the telephone line with a predetermined AC impedance when the telephone line is connected to an internal circuit through the first or second high voltage switch means. 3. The no-ringing communication network control device according to claim 1, further comprising a correction unit that corrects a difference between an AC impedance formed by the circuit at the time of no ringing incoming call and an AC impedance formed at the terminal calling communication. 4. The network controller for no-ringing communication according to claim 3, wherein the correction means has a correction resistance connection means for connecting a correction resistance in parallel or in series with the termination resistance. 5. The network controller for no-ringing communication according to claim 3, wherein the correcting means separately provides a terminating resistor for no-ringing communication and a terminating resistor for terminal-calling communication as the terminating resistors. .