JPH0591210A - Network controller - Google Patents

Abstract

PURPOSE:To provide both functions of the no-ringing incoming call signal system and the terminal dial system with simple configuration and to isolate the controller from a telephone line electrically so that the controller is used by a battery and a commercial power supply as the power supply. CONSTITUTION:In the case of no-ringing incoming call, a switch 4 is closed and after the polarity of a line voltage is inverted, when a voltage detection circuit 6 detects the voltage to be a prescribed voltage or over via a high dielectric strength switch circuit 3, no-ringing communication is started through a capacitor C9 and a communication transformer 10 and when the call is finished, a high dielectric strength switch control circuit 5 is operated by an end signal from a control circuit 11 to make the circuit 3 nonconductive. In the case of a call at a terminal equipment, the switch 4 is turned off tentatively by a line check control signal from the circuit 11 and then turned on again, and a voltage detection signal of the circuit 6 is changed via the circuit 3 with an output voltage of a bridge 2 in response to the line voltage and the circuit 11 discriminates the operating state of a telephone line accordingly.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a network control device provided between a telephone line and a terminal device.

[0002]

2. Description of the Related Art A network control device of this type is used, for example, by connecting a terminal device for reading meters for electricity, gas, water, etc. to a telephone line, and measuring the amount of water, gas, electricity, etc. used by the terminal device. Is used for a data collection system that transmits usage data to a center device, which is a central data collection management device, via a telephone line, and the center device collects usage data. In addition,
This data collection system includes, for example, a system for calling the terminal device from the center device and a system for calling the terminal device from the terminal device. In the following description, the system for calling the terminal device will be described. explain.

FIG. 8 is a system configuration diagram of a data collection system of such a terminal calling system. In this data collection system, the terminal side network control device 23 connected to the terminal device 21 is connected to the telephone exchange 2 via the terminal side telephone line 31.
5, a telephone line 33 on the center side and a network control device 27 on the center side with an automatic receiving function from the telephone exchange 25.
It is connected to the terminal calling center device 29 via.
A telephone 35 is connected to the terminal side telephone line 31 to which the terminal side network control device 23 is connected, via the terminal side network control device 23. That is, the terminal side network control device 2
3 has telephone line connection terminals L1 and L2 and other terminal device connection terminals T1 and T2, and telephone line connection terminals L1 and L2
The terminal side telephone line 31 is connected to, and the telephone set 35 is connected to the other terminal device connection terminals T1 and T2. The telephone 35 may be another network control device such as the terminal side network control device 23.

In the data collection system thus configured, the terminal device 21 captures the terminal side telephone line 31 of the telephone exchange 25 through the terminal side network control device 23, and the telephone of the terminal calling center unit 29 is called. A series of processes for calling the terminal calling center device 29, such as dialing a number and detecting a response of the terminal calling center device 29, are performed,
After calling the terminal calling center device 29, the meter reading data or the like is transmitted to the terminal calling center device 29, whereby the terminal calling center device 29 collects the data.

By the way, in order for the terminal device 21 to perform the calling operation for capturing the terminal side telephone line 31 via the terminal side network control device 23, it is necessary to confirm that the terminal side telephone line 31 is empty.
That is, it is necessary to identify by the terminal side network control device 23 that the telephone 35 connected to the same terminal side telephone line 31 is not using the terminal side telephone line 31 and that there is no incoming call from the telephone exchange 25. Then, the terminal side network control device 23 confirms that the terminal side telephone line 31 is free before making a call.

In order to detect whether the above-mentioned terminal side telephone line 31 is in use and whether or not there is an incoming call at the terminal side telephone line 31, the terminal side network control device 23 is conventionally used.
A circuit as shown in FIG. 9 is used. That is, the telephone line connection terminals L1 and L to which the terminal side telephone line 31 is connected
Two photocouplers 41, 4 are connected to one of the connection terminals L2.
The three light emitting diodes 41d and 43d are connected in parallel and in opposite directions. These photo couplers 41,
The phototransistors 41t and 43t of 43 have their emitters connected to a common ground, and their collectors have a resistor 41t.
It is connected to the power supply Vd via r and 43r, and detection signals S1 and S2 are output from both collectors, respectively. A series circuit including a check switch 45 and a resistor 47 is connected between the telephone line connection terminals L1 and L2 through the light emitting diodes 41d and 43d of the photocouplers 41 and 43 connected in parallel.
Further, the series circuit including the check switch 45 and the resistor 47 is connected to the off-hook / dial switch 4
A direct circuit composed of 9 and a resistor 51 is connected in parallel. The other terminal connection terminals T1 and T2 are connected between the telephone line connection terminals L1 and L2 via the light emitting diodes 41d and 43d of the photocouplers 41 and 43, that is, in parallel with the series circuit of the check switch 45 and the resistor 47. It is connected. The conventional checking of whether the terminal side telephone line 31 is in use and the presence or absence of an incoming call when the terminal side network control device 23 configured as described above performs a calling operation will be described. First, regarding whether or not the terminal side telephone line 31 is in use, this is connected to the same terminal side telephone line 31 via the other terminal device connection terminals T1 and T2 of the terminal side network control device 23. It suffices to detect the state where the telephone 35 being hooked is off-hook. When the telephone 35 is off-hook, the telephone exchange 2
Terminal side telephone line 31 and telephone 3 by the power supply from 5
Light-emitting diodes 41d and 43d through the off-hook of 5
It is only necessary to detect that a current is flowing in any of the above and any of them is conducting. Specifically, the telephone exchange 2 is connected to the telephone line connection terminal L1 via a corresponding telephone line.
5 is connected to the ground, and the telephone line connection terminal L2 is connected to the telephone exchange 25 through the corresponding telephone line.
Since the DC voltage of 48v is supplied, when the telephone 35 goes off-hook, the telephone line, the telephone line connection terminal L1, the terminal side network control device 23, the other terminal device connection terminal T1 and the telephone set off-hook from the ground of the telephone exchange 25. 35, the other terminal device connection terminal T2, the terminal side network control device 23, the light emitting diode 41d, the telephone line connection terminal L2, a current flows through the telephone line 25 to the -48v power source of the telephone exchange 25, thereby causing the photocoupler 41 to operate. Photo transistor 41t
The detection signal S1 is output from the device, so that the telephone 35 is known to be in use. When the telephone 35 is not off-hook and is not in use, the current does not flow, so that the phototransistors 41t and 43t of the photocouplers 41 and 43 are both non-conducting, and therefore are not in use. I understand.

When an incoming call is received from the telephone exchange 25 for calling the terminal device 21, a calling signal is supplied from the telephone exchange 25 via the terminal side telephone line 31, and the terminal from the telephone exchange 25 is supplied. The voltage polarity with respect to the side telephone line 31 is reversed, and the telephone line connection terminal L1 of the terminal device 21 is connected to the telephone exchange 25 through the corresponding telephone line.
From the telephone exchange 25 through the corresponding telephone line to the telephone line connection terminal L2. Therefore, the terminal side network control device 23 can detect whether or not there is an incoming call by detecting this state. Therefore, the terminal side network control device 23 turns on the check switch 45 for this purpose, and the telephone exchange. A loop having a large resistance with respect to the telephone line connection terminals L1 and L2 is formed via a relatively large resistance 47 such that 25 does not detect the loop. As a result, when there is an incoming call from the telephone exchange 25 with the above-mentioned reverse polarity, the corresponding telephone line from the ground of the telephone exchange 25, the telephone line connection terminal L2, and the photocoupler 43 of the terminal side network control device 23.
Current flows through -48v of the telephone exchange 25 through the light emitting diode 43d, the resistor 47, the check switch 45, the telephone line connection terminal L1, and the corresponding telephone line, which causes the detection signal S2 from the phototransistor 43t of the photocoupler 43. Is output, so that the incoming call can be recognized from the telephone exchange 25.

As a method of calling the terminal device from the center apparatus, a method based on no ringing incoming call is used, and there is a network controller for no ringing incoming call for this no ringing incoming call method. The detection or color of the no-ringing incoming call signal in this no-ringing incoming call network control device is described in, for example, Japanese Patent Application No. 2-121889. A feature of the network controller for no-ringing incoming call of this patent is that the no-ringing incoming call signal can be detected regardless of the polarity of the telephone line.

Therefore, if the circuit of FIG. 8 described above is added to the no-ringing incoming call network control device of this patent, a network control device having both a no-ringing incoming signal detection function and a terminal calling function can be constructed. Is possible.

[0010]

As described above, the method of realizing the terminal calling function by adding the circuit of FIG. 8 to the no-ringing incoming call network control device is a method of using a plurality of photocouplers, switch elements, and the like. There is a problem that it requires expensive parts and is uneconomical.

When a commercial power source (100 VAC, for example) is used as a power source for such a network control device, the circuit portion connected to the telephone line and the commercial power source operate in consideration of the insulation between the commercial power source and the telephone line. It is necessary to electrically separate the circuit portion to be used. At this time, such a network control device could not be separated.

The present invention has been made in view of the above,
It is an object of the present invention to provide a network control device which achieves a terminal calling function with a relatively simple structure and can be electrically separated from a telephone line.

[0013]

In order to achieve the above object, the present invention provides a terminal calling function which is connected between a telephone line and a terminal device and calls a telephone line in response to a calling request from the terminal device. In a network control device having a function of detecting the polarity reversal of the line voltage due to no ringing call from the telephone line, a diode bridge connected between the telephone lines so that the voltage polarity of the line voltage is aligned in a certain direction, and a diode bridge. Inputting the output voltage of the first switch, and conducting a switch when the voltage value falls within a predetermined range;
The voltage detection means that operates with the output voltage of the diode bridge that passes through the switch means to output a voltage detection signal and the line check control signal, and the telephone based on the voltage detection signal from the voltage detection means at this time First communication means for determining whether or not the line is in use, and after completion of communication by the no ringing call from the telephone line, the first switching means is made non-conductive by a completion signal from the first control means. Based on the second control means, the second switch means provided between the diode bridge and the first switch means, which performs the opening / closing operation by the line check control signal, and the discrimination signal from the first control means. It is composed of a line closing means for closing the telephone line when the telephone line is not used.

[0014]

In the network control device of the present invention, when the output voltage of the diode bridge falls within a predetermined range, the first switch means conducts to supply the output voltage to the voltage detecting means, and the first control means causes the line to operate. A check control signal is output to control the opening and closing of the second switch means, and thereafter, it is determined whether the telephone line is in use based on the voltage detection signal of the voltage detection means, and the line is determined by the determination signal. When the telephone line is closed by activating the closing means, and when calling no ringing,
After the communication is completed, a completion signal is output and the first switch means is made non-conductive through the second control means, so that the terminal calling function is realized with a simple configuration and electrically separated from the telephone line. Will be possible.

[0015]

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

FIG. 1 is a block diagram showing the configuration of a network control device according to an embodiment of the present invention. The network control device shown in the figure has telephone line connection terminals 1a, 1 connected to a telephone line.
b, and the telephone line connection terminals 1a and 1b are connected to the input of the diode bridge 2. This diode bridge 2 is for converting the polarity of the DC voltage from the telephone line supplied from the telephone line connection terminals 1a and 1b to a fixed direction. From the diode bridge 2 whose polarity is set to a fixed direction by the diode bridge 2. Output voltage, that is, the DC voltage from the telephone line is supplied to the high breakdown voltage switch circuit 3. The high breakdown voltage switch circuit 3 becomes conductive when the DC output voltage from the diode bridge 2 rises above a second predetermined voltage, and thereafter, even if the DC output voltage becomes a voltage lower than the second predetermined voltage. The continuity is maintained.

Further, the high withstand voltage switch circuit 3 is in a cut-off state when the DC output voltage from the diode bridge 2 becomes equal to or higher than a first predetermined voltage which is higher than the second predetermined voltage when in the conducting state, and thereafter. Keeps the cutoff state even when the DC output voltage becomes lower than the first predetermined voltage. Furthermore, the high voltage switch circuit 3
When in a conductive state, a high voltage switch control circuit 5 described later
When the cutoff signal is input from, the cutoff state is entered, and thereafter, the cutoff state is maintained even after the cutoff signal is released. The switch 4 is normally in the ON state, which will be described later.

When the high breakdown voltage switch circuit 3 becomes conductive, the DC output voltage from the diode bridge 2 is supplied to the voltage detection circuit 6 in the subsequent stage via the high breakdown voltage switch circuit 3. The voltage detection circuit 6 starts its operation by the electric power supplied from this DC voltage and outputs a detection signal. Therefore, when the high withstand voltage switch circuit 3 changes from the cut-off state to the conductive state, the voltage detection circuit 6 always generates a detection signal.

The no-ringing signal detection circuit 6 is AC-connected to the output of the high breakdown voltage switch circuit 3 via a capacitor 15, and when activated by the detection signal 8 from the voltage detection circuit 4, the high breakdown voltage switch circuit 6 is activated. A non-ringing incoming signal (NRS signal) superimposed on the DC voltage from the diode bridge 2 via 3 is detected, and this detection signal is supplied to the control circuit 7. The control circuit 11 catches the change of the line voltage at the time of no ringing call, and when the voltage detection circuit detects via the diode bridge 2 that the voltage becomes equal to or higher than a predetermined voltage, the control circuit 11 determines that it is called.

On the output side of the diode bridge 2, a line closing circuit 7 is connected in parallel with the switch 4, and the line closing circuit 7 is operated by a discrimination signal from the control circuit 11 to output the output of the diode bridge 2. Short the sides, which closes the telephone line and puts it off-hook.

After the completion of the no-ringing communication, the high breakdown voltage switch circuit 3 is made non-conductive by the high breakdown voltage switch control circuit 5 which operates by the completion signal from the control circuit 11.

The voltage detection circuit 6 is a high voltage switch circuit 3
Therefore, a voltage higher than the first predetermined voltage higher than the second predetermined voltage is detected, and this voltage detection signal is supplied to the control circuit 11.

FIG. 2 is a detailed circuit diagram of the network controller of FIG. As shown in detail in FIG.
Has a switching transistor Q31 connected in series to the output of the diode bridge 2 via a switch 4, and the output of the diode bridge 2 connected to the emitter of the transistor Q31 has resistors R34 and R3.
5, the zener diode ZD31 having a zener voltage (for example, 35V) corresponding to the second predetermined voltage, and the transistor Q32 are connected to the ground. A transistor Q34 is connected in parallel to both ends of the Zener diode ZD31. The transistor Q3
The base of No. 4 is connected to the collector of the transistor Q31 via the diode D33 and the resistor R36, and the resistor R38 is connected between the base and the emitter of the transistor Q34.

The output of the diode bridge 2 is connected to the ground via the resistor R32 and the transistor Q33, and is also connected to the ground via the resistor R31, the diode D31 and the capacitor C31, and the collector of the transistor Q33 is the above transistor. It is connected to the base of Q32. Further, the connection point between the resistor R31 and the diode D31 is connected to the collector of the transistor Q32 via the diode D32. Diode D
The connection point between the capacitor 31 and the capacitor C31 is a transistor Q.
It is connected to the base of 33.

Further, the collector of the transistor Q31 is
A resistor R37, a Zener diode ZD32 having a Zener voltage corresponding to the first predetermined voltage, and a diode D35 are connected to the connection point between the resistor R33 and the diode D36. In addition, the voltage detection circuit 6
Is a photocoupler PC61 which operates by being supplied with the DC output voltage from the diode bridge 2 supplied via the transistor Q31, that is, the DC voltage from the telephone line.
Have.

The collector of the transistor Q31 of the high breakdown voltage switch circuit 3 is connected to the primary side of the communication transformer 10 via the capacitor C9. On the other hand, the line closing circuit 7 is connected to the ground via the switch 7 and the resistor R71, and is also connected to the communication transformer T10 via the capacitor C8. The line closing circuit 7 is activated by the determination signal of the control circuit 11 to close the telephone line. .. Next, the operation of the network control device configured as described above will be described. First, the operation at the time of no ringing incoming call will be described with reference to FIGS. 3 and 4.

First, when the switch 4 is in the ON state, the Zener diode ZD31 starts from the low voltage supplied from the telephone line between the telephone line connection terminals 1a and 1b.
When the voltage rises above the second predetermined voltage which is the Zener voltage of irrespective of the polarity (voltage between FIG. 3, 3a and 3b), this voltage is aligned in a fixed direction by the diode bridge 2.
The high voltage switch circuit 3 is supplied with a positive voltage. Then, this voltage is applied to the transistor Q via the resistor R31 and the diode D31 of the high breakdown voltage switch circuit 3.
In addition to being supplied to the base of 33, it is supplied to the base of the transistor Q32 via the resistor R32, and tries to energize both transistors. However, transistor Q33
Since the capacitor C31 is connected to the base of the transistor Q31 and the voltage supplied to the base of the transistor Q33 is charged in the capacitor C31, the voltage at the base of the transistor Q33 does not rise and therefore the transistor Q33 does not conduct. On the other hand, the collector of the transistor Q33 is connected to the base of the transistor Q32, but since the transistor Q33 does not conduct, the base potential of the transistor Q32 rises and the transistor Q32 conducts. As a result, the potential of the resistor R31 decreases via the diode D32, and the base potential of the transistor Q33 becomes Vf potential or lower. Therefore, the transistor Q33 is suppressed in the cutoff state, and only the transistor Q32 is stable in the conductive state.

On the other hand, the DC voltage from the diode bridge 2 is applied to the resistors R34 and R35 connected to the emitter of the transistor Q31 and the Zener diode ZD3.
1. The voltage is supplied to the Zener diode ZD31 through the path of the transistor Q32 in the conductive state. The DC voltage at this time is the Zener voltage of the Zener diode ZD31.
Zener diode ZD
31 becomes conductive, a current flows, a voltage is generated across the resistor R34, and this voltage is Vf of the transistor Q31.
When the voltage is reached, the transistor Q31 becomes conductive. When the transistor Q31 becomes conductive, a voltage is generated on the collector side through the transistor Q31, which causes the resistor R36.
And a current flows through the resistor R38 through the diode D33, and the voltage across the resistor R38 causes a transistor Q
34 also conducts. When the transistor Q34 becomes conductive, a current route that bypasses the Zener diode ZD31 is formed, and thereafter, even if the DC voltage from the telephone line via the diode bridge 2 and the transistor Q31 drops, the transistor Q31 continues to be in the conductive state.

When the transistor Q31 becomes conductive,
A DC voltage is supplied to the voltage detection circuit 6 via the transistor Q31, and a current flows through the resistor 61 → photocoupler PC61 / diode, so that the photocoupler PC61 operates and the polarity inversion of the telephone exchange 25 can be detected. (FIG. 3, No Ringing Call Detection). After detecting the extreme reversal, through the capacitor C9 and the communication transformer T10,
Performs a series of operations for no ringing communication.

On the other hand, when the communication started by the no ringing call is completed, the control circuit 11 outputs a completion signal to the high voltage switch control circuit 5. As a result, the photocoupler PC51 of the high withstand voltage switch control circuit 5 is turned on, C31 is charged through the diode D36 and the resistor R33, and when the base potential of the transistor Q33 becomes the Vf voltage, the transistor Q33 becomes conductive. .. When the transistor Q33 becomes conductive, the base potential of the transistor Q32 drops, and the transistor Q32 is cut off. When the transistor Q32 is cut off, the base current of the transistor Q31 stops flowing, so that the transistor Q31 is cut off. When the transistor Q32 is cut off, the diode D32
Since the potential of the transistor rises, the current stops flowing through the diode D32, whereby the transistor Q33 maintains the conductive state and the transistor Q32 stabilizes in the cutoff state. That is, due to the action of the capacitor C31, the high withstand voltage switch circuit 3 becomes non-conductive with a slight delay after the completion signal is output.
As a result, the voltage detection circuit 6 stops (see FIG. 4). In addition, the DC voltage of the telephone line is the Zener diode ZD32.
First predetermined voltage (eg, 60V) that is the Zener voltage of
When the voltage rises above the above, a current flows through the Zener diode ZD32, and this current flows through R37 and the Zener diode ZD3.
2, the capacitor C31 is charged through the diode D35 and the resistor R33, and the same operation as when the completion signal is supplied is performed. Next, with reference to the timing charts shown in FIGS. 5 to 7, the line in-use check processing when the terminal call operation is performed will be described.

Since the voltage between the telephone line connecting terminals 1a and 1b is -48V when the telephone line is not used, the voltage between the connecting points 3a and 3b shown by the diode bridge 2 as shown in FIG. It is 48V, which is higher than the second predetermined voltage of the Zener diode ZD31.

At the time of checking the line use, the control circuit 11
A line check control signal is output to switch the switch 4 from the ON state to the OFF state, and then the switch 4 is turned on again.
As a result, as shown in FIGS. 5 to 7, the input voltage (voltage between 3a and 3b) of the high breakdown voltage switch circuit 3 undergoes a voltage change similar to that at the time of polarity reversal.

Therefore, as described above, the transistor Q
32 is made conductive, and the transistor Q31, the resistor R35, the zener diode ZD31, and the resistor R35 are connected by the voltage between the connection points 3a and 3b, which is equal to the voltage between the telephone line connection terminals 1a and 1b.
A current flows through the transistor Q32 in the conductive state, whereby the transistor Q31 becomes conductive, that is, the high breakdown voltage switch circuit 3 becomes conductive, and the DC voltage from the diode bridge 2 is supplied to the voltage detection circuit 6. In this state,
Even if the line check control signal disappears, the output of the diode bridge 2 passes through the resistor R32 and the transistor Q
Current continues to flow to the base of 32, and the transistor Q32 continues to be conductive, whereby the conductive state of the transistor Q31 is maintained.

When the DC voltage from the diode bridge 2 is supplied to the voltage detection circuit 6 via the conductive high-voltage switch circuit 3, the operation similar to that at the time of no ringing incoming call occurs.
If the line is unused (voltage is 48 V), the Zener voltage ZD31 or higher, so the photocoupler (PC61) of the voltage detection circuit 6 is turned on and the voltage detection signal is output.

Therefore, this voltage detection signal is kept for a certain time T.
By monitoring the output (for example, about 2 seconds), the unused state of the telephone line can be identified. In addition,
The reason why it is determined that there is a continuous presence of 2 seconds or more is
This is because the 75 V, 16 Hz calling signal supplied from the exchange to the telephone is sent by repeating 1 second sending and 2 second rest.

Next, with reference to the timing chart shown in FIG. 6, the line busy check processing for performing the terminal call operation when the telephone line is being used by the telephones connected in parallel will be described.

Since the voltage between the telephone line connection terminals 1a and 1b is about 6 V when the parallel-connected telephone is in use, the connection point 3a-output from the diode bridge 2 is
The voltage between 3b is 6V, and the Zener diode ZD3
It is lower than the second predetermined voltage of 1. When the line in use is checked in this state, the high withstand voltage switch circuit 3 does not conduct because the line voltage is the Zener voltage ZD31 or less. That is, no voltage detection signal is output from the voltage detection circuit 6. This allows the control circuit 7 to identify that the telephone line is in use by the telephone.

Next, with reference to the timing chart shown in FIG. 7, the line in-use check processing for performing the terminal call operation when the telephone call signal (75 V, 16 Hz) is being received will be described.

In the state where the call signal is arriving, the voltage between the connection points 3a and 3b output from the diode bridge 2 which is equal to the voltage between the telephone line connection terminals 1a and 1b is synchronized with the transmission of the signal for 2 seconds and for 1 second. 48V and a voltage in which 75V and 16Hz are superimposed on this 48V, and as shown in the figure, the second predetermined voltage of the Zener diode ZD31 is generated in the negative cycle portion of the calling signal of 75V and 16Hz. Is lower than.

When the line busy check is performed when the telephone call signal is transmitted from the telephone exchange 25, when the signal is in a stopped state,
As described above, the voltage detection circuit 6 outputs the voltage detection signal.

Call signal is 48V to 75V, 16H
When it changes to z and becomes equal to or higher than the Zener voltage of the Zener diode ZD32, that is, the first predetermined voltage, the voltage detection signal of the voltage detection circuit 6 is output to the control circuit 11, and the current passing through the Zener diode ZD32 is changed to the resistance R.
Since the capacitor C31 is charged via 33, when this charging voltage becomes equal to or higher than the V _BE voltage of the transistor Q33,
Transistor Q33 becomes conductive, which causes transistor Q32 to become non-conductive, and transistor Q31,
That is, the high voltage switch circuit 3 is turned off. Therefore, the voltage detection signal of the voltage detection circuit 6 stops.

Note that once the transistor Q33 is turned on, even if the line voltage of 75V, 16Hz superimposed on DC 48V fluctuates, the transistor Q33 is connected by the capacitor C31 connected to the base of the transistor Q33.
Is kept conductive, and the high breakdown voltage switch circuit 3 does not become conductive.

Therefore, since the voltage detection signal is output for 1 second and stopped for 2 seconds while the call signal is being received,
By identifying these signals, it is possible to identify when the telephone line is in use. Next, the line closing operation at the time of making a call from the terminal after the line in use check has identified that the line is not in use will be described. After identifying that the line is not in use and confirming that the terminal can make a call, the control circuit 11 supplies a determination signal to the line closing circuit 7 to close the line.

In the description of the present invention, for simplification,
Although the switches SW4 and SW7 are composed of relays, the same function as that of the present invention can be realized even if the switches SW4 and SW7 are composed of semiconductor elements such as photocouplers.

[0045]

As described above, according to the present invention, the terminal calling function, which is connected between the telephone line and the terminal device and calls the telephone line in response to the calling request from the terminal device, and the no ringing from the telephone line. In a network control device having a function of detecting the polarity reversal of the line voltage due to calling, input a diode bridge connected between telephone lines so that the voltage polarity of the line voltage is aligned in a certain direction, and the output voltage of the diode bridge, First switch means that conducts when the voltage value falls within a predetermined range, voltage detection means that operates by the output voltage of the diode bridge that passes through the first switch means and outputs a voltage detection signal, and line check control A first control means for outputting a signal and determining whether or not the telephone line is in use based on the voltage detection signal from the voltage detection means at this time; Is provided between the diode bridge and the first switch means, and second control means for making the first switch means non-conductive by the completion signal from the first control means after the completion of communication by the no ringing call from The second that opens and closes according to the line check control signal
The switch calling means and the line closing means for closing the telephone line based on the discrimination signal from the first control means when the telephone line is not used, the terminal calling function has a relatively simple structure. By achieving the above and electrically separable from the telephone line, it is possible to obtain a network control device which can use a battery and a commercial power source as a power source.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a network control device of the present invention.

FIG. 2 is a detailed circuit diagram of FIG.

FIG. 3 is a timing chart showing the operation of [FIG. 1] and [FIG. 2].

FIG. 4 is a timing chart showing the operation of [FIG. 1] and [FIG. 2].

FIG. 5 is a timing chart showing the operation of [FIG. 1] and [FIG. 2].

FIG. 6 is a timing chart showing the operation of [FIG. 1] and [FIG. 2].

FIG. 7 is a timing chart showing the operation of [FIG. 1] and [FIG. 2].

FIG. 8 is a block diagram of a data collection system of a terminal calling method.

FIG. 9 is a conventional circuit diagram for checking the line usage status.

[Explanation of symbols]

2 ... Diode bridge, 3 ... High breakdown voltage switch circuit, 4 ... Switch 5 ... High breakdown voltage switch control circuit, 6 ... Voltage detection circuit,
7 ... Circuit closing circuit 11 ... Control circuit

Claims (1)

[Claims] 1. A connection between a telephone line and a terminal device,
In a network control device having a terminal calling function for calling a telephone line in response to a calling request from a terminal device and a function for detecting a polarity reversal of the line voltage due to a no ringing call from the telephone line, a voltage polarity of the line voltage With a diode bridge connected between the telephone lines so that they are aligned in a certain direction, with the output voltage of the diode bridge being input, and with the first switch means conducting when the voltage value falls within a predetermined range, and the first switch means. A voltage detection means that operates by the output voltage of the diode bridge that passes through the switch means to output a voltage detection signal, and a line check control signal, and the telephone based on the voltage detection signal from the voltage detection means at this time First control means for determining whether or not the line is in use, and after completion of communication by the no ringing call from the telephone line, before A second control means for turning off the first switch means in response to a completion signal from the first control means and the diode bridge and the first switch means are provided. A network control device having a second switch means for performing an opening / closing operation and a line closing means for closing a telephone line when the telephone line is not in use based on a discrimination signal from the first control means.