JPH06261140A - Terminal network controller - Google Patents

Abstract

PURPOSE:To provide a terminal network controller which can perform the communication by the no-ringing incoming and the automatic outgoing, can reduce the waveform distortion of a dial pulse, and also can use an IC of low withstand voltage. CONSTITUTION:A terminal network controller consists of a closing means 1 which controls the termination and opening with a DC impedance in a terminal calling communication state, a half-closing means 9 which performs the termination with a DC impedance in a no-ringing communication state and outputs the signal transmitted from a modem, a switch means 16 which switches the AC impedance according to a dial pulse transmission state, a no-ringing incoming detection state or a communication state, and a connector means 22 which connects the means 1, 9 and 12 to a telephone circuit L2.

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 connected between a telephone line and a terminal device, and in particular, it is activated by receiving a no-ringing signal sent from an exchange through the telephone line, and the terminal device is activated by the telephone line. The present invention relates to a terminal network control device having both a function of connecting to a terminal and a function of enabling a call operation from a terminal device.

[0002]

2. Description of the Related Art Recent telephones are equipped with a speech path IC for sending an AC signal such as voice to a telephone line by closing a DC loop circuit of the telephone line by simply hooking the handset off hook. Since this IC has a withstand voltage of about 15 V, it is relatively inexpensive. The line voltage of the telephone line is about 48V when the DC loop circuit is open, but it is 50V when the DC loop circuit is closed.
10 to terminate with DC impedance of Ω to 300Ω
It will be about V. The termination of the AC impedance is made by a resistor and capacitor RC circuit.

FIG. 3 shows an example of a circuit of a conventional terminal device. A telephone line is connected to the terminals L1 and L2, a switch S is connected between the terminal L2 and the output terminal 0 of the communication path IC1, and the terminal L1 is grounded. A protection zener diode ZD1 with a zener voltage of 12 V is connected between the output terminal 0 of the communication path IC1 and the ground point, and the collector and emitter of the transistor Q1 of the communication path IC1 are connected via a resistor R1. Has been done. A series connection of resistors R2, R3 and R4 is connected between the collector and emitter of the transistor Q1, and the base of the transistor Q1 and the output terminal of the operational amplifier A are connected to the connection point of the resistors R3 and R4. . The value of the resistor R1 is set so that the DC impedance of the line is 50Ω to 300Ω. Resistance R2
Since the connection point between the resistor R3 and the resistor R3 is grounded via the large-capacity capacitor C1, it is possible to match the AC impedance for transmitting and receiving a voice signal or the like to 600Ω. As an example, the resistance R2 is 600Ω, and the resistances R3 and R4 are each several tens of KΩ. Transmitting circuit T for transmitting audio signal
Is connected to the input terminal of the operational amplifier A. Further, a receiving circuit R for receiving an audio signal is connected to the terminal L2 via the capacitor C2 and the switch S.

When the switch S is closed, the transistor Q1 is turned on by the line voltage and the DC loop of the telephone line is closed. Also, the transmission of the dial pulse is achieved by turning on / off the switch S. The charging time constant of the capacitor C1 for matching the AC impedance to 600Ω is large, but since the Zener voltage of the Zener diode ZD1 is as low as 12V, it is not affected by the charging time constant when the switch S is closed, and the square wave dial is used. Pulses can be output on the line.

On the other hand, there is a terminal network control device developed for a telecontrol system for connecting a gas meter, a water meter or the like to a terminal and performing automatic meter reading, automatic notification and remote control with a communication service center. This network control device is equipped with a no-ringing receiving means for accepting calls from the center (for automatic meter reading) using the no-ringing communication service of the telephone network, and an automatic calling means for calling the center to automatically notify of gas leaks. ing. When making an automatic call, the DC loop circuit is terminated with a low DC impedance as with a telephone, but in this no-ringing incoming communication, it is terminated with a high DC impedance of several tens of KΩ or more when an incoming call is detected, and 4 KΩ or more during no-ringing communication, so there is almost no voltage drop. Does not happen. The closing of this DC loop circuit is called semi-closing. And
As described above, an active element IC having a high breakdown voltage is required when the direct current loop circuit is semi-closed to form a speech path.

[0006]

The problems to be solved by the present invention include the following two points. (1) In order to enable no ringing incoming call and automatic outgoing call, it is necessary to switch the DC impedance and the AC impedance between the closed state and the semi-closed state. Also,
In order to use the switch S for both closing and half-closing of the DC impedance matching circuit, the Zener voltage of the Zener diode ZD1 must be about 48V, and the discharge of the capacitor C1 for matching the AC impedance to 600Ω.
The dial pulse does not become a square wave because the charging time constant is large. (2) A high withstand voltage IC is required for a communication path IC capable of receiving no ringing by using the switch S for both closed and semi-closed states of the DC impedance matching circuit, which increases the cost.

A first object of the present invention is to provide a network control device for a terminal, which is capable of communication by no ringing incoming call and automatic outgoing call and can send a square wave dial pulse. A second object of the present invention is to provide a terminal network control device. It is an object of the present invention to provide a terminal network control device which can use a low withstand voltage communication path IC capable of receiving no ringing.

[0008]

In order to achieve the first object of the present invention, the present invention has a closing means for controlling termination and opening at a DC impedance during terminal call communication, and a DC impedance during no ringing communication. Semi-closed means for terminating the transmission signal from the modem and outputting an output signal from the modem, AC impedance switching means for switching the AC impedance depending on whether the dial pulse is transmitted or during the communication, the closing means and the half-closed during the communication. And a connecting means for connecting the AC impedance switching means to a telephone line.

Further, in order to achieve the second object, a closing means for terminating with a DC impedance during a terminal call communication, and a signal output from a modem for terminating with a DC impedance during no ringing communication. Semi-closing means including a variable resistance part for changing the resistance value by means of, an AC impedance switching means for switching the AC impedance depending on whether an incoming call is detected or during communication, and a first connection for connecting the closing means to a telephone line. And a second connecting means for connecting the semi-closing means and the AC impedance switching means to a telephone line.

[0010]

According to the structure described in claim 1, the connecting means at the time of calling the terminal connects the closing means, the semi-closing means and the AC impedance switching means to the telephone line, whereby impedance matching at the time of closing is achieved. The signal from the modem is sent to the telephone line through the semi-closing means. The AC impedance switching means can reduce the time constant of the termination at the time of sending the dial pulse in the terminal call. Further, when the no-ringing signal is received, the closing means is kept open, and the semi-closing means and the AC impedance switching means are connected to the telephone line. This terminates the impedance in the semi-closed state, and the signal from the monitor is sent to the telephone line through the semi-closed means.

According to the structure of the second aspect, the circuit voltage of about 12 V is applied to the closing means only when the closing means is connected to the telephone line by the first connecting means. Further, when the no-ringing signal arrives, the semi-closed means is connected to the telephone circuit by the second connection means while the first connection means is turned off. Therefore, the circuit voltage in the semi-closed state is supplied only to the variable resistor portion. Is applied.

[0012]

Embodiments Embodiments will be described below with reference to the drawings.

FIG. 1 is a block diagram of a terminal network controller according to a first embodiment of the present invention. Output terminal 2 of closing means 1
Between the collector and the emitter of the transistor 3 is connected between the collector and the base of the transistor 3 through the resistor 4, the resistor 5 is connected between the collector and the base of the transistor 3, and the resistor 6 is connected between the base and the emitter of the transistor 3. . A capacitor 7 and a switch 8 are connected between the base of the transistor 3 and the ground point.

Between the output terminal 10 of the semi-closing means 9 and the grounding point, the collector and emitter of the transistor 11 are connected via a resistor 12, and the base of the transistor 11 has a resistor 13 and a resistor 14. Is connected to the voltage dividing circuit for bias voltage and the signal output terminal of the operational amplifier 15.

A 600 Ω resistor 18, a large-capacity capacitor 19 and a small-capacity capacitor 20 are connected in series between the output terminal 17 of the AC impedance switching means 16 and the ground point. The connection point between the capacitor 20 and the small-capacity capacitor 20 is grounded via the switch 21.

The output terminal 2 of the closing means 1, the output terminal 10 of the semi-closing means 9 and the output terminal 17 of the AC impedance switching means 16 are connected to the terminal L2 via the connecting means 22. Reference numeral 23 is a transmitting circuit, 24 is a receiving circuit, and 25 is a coupling capacitor of the receiving circuit 24.

In such a structure, the operation when the no-ringing signal arrives will be described first.

When the no-ringing signal arrives, the switch 8 of the closing means 1 is closed and the switch 21 of the AC impedance switching means 16 is closed, and the connecting means 22 is turned on. As a result, the closing means 8 and the semi-closing means 9 are connected to the telephone line.
And the AC impedance switching means 16 is connected.
However, since the transistor 3 is off when the switch 8 of the closing means 1 is closed, it is in a high impedance state, and the telephone lines are terminated with a DC impedance of about 5 KΩ by the resistors R13, 14, 12 of the half closing means 9. It will be in a state of being. The AC impedance becomes 600Ω due to the resistor 18 and the capacitor 19. The no-ringing communication is performed in this state, and the push button dial signal and the modem signal from the transmitting circuit 23 are the operational amplifier 1 of the semi-closing means 9.
5 is sent to the telephone line. At the end of the no-ringing communication, the connection means 22 is turned off to open the telephone line. The signal is received by the receiving circuit 24 through the capacitor 25.
Done in.

Next, the operation when calling communication is performed using dial pulses will be described. First, the switch 8 of the closing means 1 is opened, and the switch 2 of the AC impedance switching means 16 is opened.
Keep 1 open. Next, the connection means 22 is turned on / off in combination and sent as a dial pulse to the line,
Connect to the center via telephone line. At this time, the DC impedance is set to a low value of about 150Ω in the parallel connection state of the closing means 1 and the semi-closing means 9, and the AC impedance switching means 16 has a resistor 18, a large-capacity capacitor 19 and a small-capacity capacitor. The capacitor 20 is connected in series, and its time constant is low. Therefore, the rising and falling edges of the output pulse become sharp. During communication, AC impedance switching means 1
6 switch 21 is closed and AC impedance is 600Ω
Then, the push button dial signal and the modem signal from the transmitting circuit 23 are output through the semi-closing means 9. The signal is received by the receiving circuit 24 as in the case of no ringing communication. At the end, the connection means 22 is turned off and the telephone line is opened.

According to the configuration of this embodiment, it is possible to perform communication by no ringing incoming call and terminal calling by the single connecting means 22. Also, the dial pulse can be transmitted without distortion when a call is made from the terminal network control device.

FIG. 2 is a block diagram of a terminal network controller according to a second embodiment of the present invention. The capacitor 7 in this configuration has one end connected to the base of the transistor 3 and the other end directly connected to the ground point. Further, the output terminal 2 of the closing means 1 is connected to the terminal L2 via the first connecting means 26.
The connection means 26 connects / disconnects the telephone line and the closing means 1. 27 is a Zener diode. The second connecting means 28 connects / disconnects the telephone line and the semi-closing means 9. Reference numeral 29 is a signal sending unit, which is a resistor 13 of several hundred KΩ connected to the operational amplifier 15 and its output terminal.
The signal from the modem is amplified and output. Reference numeral 30 denotes a variable resistance portion, which is composed of a variable resistance element 11 and a resistor 12 having a resistance of several tens of Ω, and changes its resistance value according to the voltage applied from the signal transmitting portion 29.

In the above configuration, the operation when a no ringing signal arrives will be described first. When there is no ringing incoming call, the telephone line is connected to the semi-closing means 9 by turning on the second connecting means 28, and the telephone line has a DC impedance of about 5 KΩ by the divided voltage value by the resistors 13 and 14. It will be in the state terminated by. The AC impedance becomes 600Ω due to the resistor 18 and the capacitor 19. The no-ringing communication is performed in this state, and the push button dial signal and the modem signal from the transmitting circuit 23 are sent to the telephone line through the semi-closing means 9.
The reception of the signal is performed by the receiving circuit 24 through the capacitor 25. After the end of the no-ringing communication, the second connecting means 28 is turned off to open the telephone line.

Next, the operation of making a call from the terminal network controller using dial pulses for communication will be described. In this case, with the second connecting means 28 turned off,
The connection means 26 is turned on / off in combination and sent as a dial pulse to the line to connect to the center terminal through the telephone line. Next, AC impedance switching means 16
Both the first connecting means 26 and the second connecting means 28 are turned on while the switch 21 is turned on. Communication is performed in this state, and a push button dial signal or a modem signal is output to the telephone line through the semi-closing means 9 as in the first embodiment. The signal is received by the receiving circuit 24 through the capacitor 25 as in the case of no ringing communication. At the end, both the first connecting means 26 and the second connecting means 28 are turned off to open the telephone line.

According to the structure of this embodiment, since the Zener diode 27 having a Zener voltage of about 12 V can be connected between the closing means 1 and the first connecting means 26, the closing means 1 has a low breakdown voltage. It can be configured with an IC. Further, since the semi-closing means 9 is composed of the signal sending part 29 and the variable resistance part 30, it is sufficient that the signal sending part 23 has a withstand voltage higher than the sending voltage of the operational amplifier 15. The sending unit 29 and the sending unit 29 can be formed of a low withstand voltage IC.

[0025]

As described above, according to the present invention, impedance matching can be performed at the time of call origination communication of a terminal and at the arrival of a no ringing signal, and a dial pulse with less waveform distortion can be transmitted to a telephone line. Further, according to the second configuration, the Zener voltage is 12V when the terminal calls.
Since the voltage can be limited by a Zener diode or the like, a low withstand voltage IC can be used as the closing means. Further, the semi-closing means is connected to the telephone line by the second connecting means at the time of no-ringing incoming call. However, since the signal sending portion of the semi-closing means only needs to withstand the outgoing signal voltage, a low withstand voltage element is used to reduce the cost. The circuit can be configured.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a terminal network control device according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram of a terminal network control device according to a second embodiment of the present invention.

FIG. 3 is a block diagram of a terminal connected to a conventional telephone line.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Closing means 8,21 Switch 9 Semi-closing means 16 AC impedance switching means 22 Connecting means 26 1st connecting means 28 2nd connecting means

Claims (2)

[Claims] 1. Closing means for controlling termination and opening with a DC impedance during terminal call communication, and semi-closing means for terminating with a DC impedance during no ringing communication and outputting a signal sent from a modem. An AC impedance switching means for switching the AC impedance depending on whether the dial pulse is transmitted or during the communication, and a connecting means for connecting the closing means, the semi-closing means and the AC impedance switching means to a telephone line. Network control equipment for terminals. 2. Closing means for terminating with DC impedance during terminal call communication, and variable resistance section for terminating with DC impedance during no ringing communication and changing the DC impedance according to the signal voltage sent from the modem. A semi-closed connection means, an AC impedance switching means for switching the AC impedance depending on whether a no-ringing signal is received or during the communication, a first connection means for connecting the closed connection means to a telephone line, and the semi-closed connection And a second connecting means for connecting the AC impedance switching means to a telephone line.